Peripheral PYY inhibits intracisternal TRH-induced gastric acid secretion by acting in the brain

Hong Yang, Keishi Kawakubo, Helen Wong, Gordon Ohning, John Walshdagger, and Yvette Taché

CURE: Digestive Diseases Research Center, Veterans Affairs Greater Los Angeles Healthcare System, and Digestive Diseases Division, Department of Medicine and Brain Research Institute, School of Medicine, University of California, Los Angeles, California 90073


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

The site of action of peripheral peptide YY (PYY)-induced inhibition of vagally stimulated gastric acid secretion was studied using immunoneutralization with PYY antibody in urethan-anesthetized rats. Gastric acid secretion (59 ± 7 µmol/90 min) stimulated by intracisternal injection of the stable thyrotropin-releasing hormone (TRH) analog RX-77368 (14 pmol/rat) was dose-dependently inhibited by 52%, 69%, and 83% by intravenous infusion of 0.25, 0.5, and 1.0 nmol · kg-1 · h-1 PYY, respectively. PYY or PYY3-36 (2.4 pmol/rat) injected intracisternally also inhibited the acid response to intracisternal RX-77368 by 73% and 80%, respectively. Intravenous pretreatment with PYY antibody (4.5 mg/rat), which shows a 35% cross-reaction with PYY3-36 by RIA, completely prevented the inhibitory effect of intravenously infused PYY (1 nmol · kg-1 · h-1). When injected intracisternally, the PYY antibody (280 µg/rat) reversed intracisternal PYY (2.4 pmol)- and intravenous PYY (1 nmol · kg-1 · h-1)-induced inhibition of acid response to intracisternal RX-77368 by 64% and 93.5%, respectively. These results provide supporting evidence that peripheral PYY inhibits central vagal stimulation of gastric acid secretion through an action in the brain.

immunoneutralization; vagus; dorsal vagal complex


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

PEPTIDE YY (PYY) is released by endocrine cells in the ileum in response to the presence of fatty acids in the intestinal lumen (30). PYY1-36 and PYY3-36 are the two molecular forms of PYY abundant in the blood (9). Peripheral administration of PYY produces a potent antisecretory effect that is selective for central vagally mediated stimulation of gastric acid and pancreatic exocrine secretions (24, 25), while having little, if any, effect on secretions elicited by peripherally acting exogenous secretagogues (24). Convergent studies indicate that the inhibition of gastric and pancreatic secretory and motor functions elicited by peripheral PYY involves a central vagal dependent mechanism. Circulating PYY may enter the brain through the area postrema and portions of the nucleus of the solitary tract (NTS), where the blood-brain barrier is incomplete and can be the portal of entry for circulating peptide hormones (10). PYY binding sites are presented in the area postrema and the dorsal vagal complex (DVC) (7, 18), which includes the NTS and the dorsal motor nucleus of the vagus (DMN) (16). The PYY derivatives [Leu31,Pro34]PYY (or Pro34 PYY) and PYY3-36 (or PYY13-36) show selective affinity to Y1 and Y2 receptors, respectively (1). Specific [125I][Leu31,Pro34]PYY (Y1) and [125I]PYY3-36 (Y2) binding sites have been detected in the NTS and the area postrema (7). PYY infused into peripheral circulation at physiological concentrations gains access to PYY binding sites located in specific portions of the DVC (12). In addition, peripheral injection of PYY activates neurons in the area postrema and dorsomedial NTS, as shown by Fos induction in these areas (4). Microinjection of PYY or PYY13-36 into the DVC inhibits gastric motility through Y2 receptors (6), whereas PYY or Pro34 PYY stimulates gastric motility and acid secretion through Y1/PYY-preferring receptors (6, 39). Both PYY and PYY13-36 administered in vivo, or in vitro to brain stem slice preparation, inhibit the activity of cholinergic vagal efferent neurons in the DMN, suggesting mediation through Y2 receptors (5). However, despite these convergent findings supporting a possible action of circulating PYY in the brain, direct evidence showing that the antisecretory effect of peripheral PYY is initiated at a central site is still lacking.

In vivo immunoneutralization has been extensively used to inhibit the biological actions of gastrointestinal peptides or neuropeptides and to assess their physiological relevance in the brain or periphery (32, 40, 41). Antibodies do not necessarily require access to intracellular compartments to inhibit peptide action and are extremely stable within biological tissues (36, 37). Antibodies administered into the lateral ventricles have been shown to diffuse through brain tissue (34, 35) and to become concentrated at sites expressing the immunogenic epitopes (31). In the present study, we first established that the specific PYY polyclonal antibody [Center for Ulcer Research and Education (CURE) no. 9153] injected intravenously or intracisternally prevents intravenous or intracisternal PYY-induced inhibition, respectively, of the acid response to central thyrotropin-releasing hormone (TRH) analog, and second, we administered the antibody intracisternally to assess whether peripherally infused PYY inhibits gastric acid secretion at a central site.


    MATERIALS AND METHODS
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Animals. Male Sprague-Dawley rats (Harlan Laboratory, San Diego, CA) weighing 250-310 g were maintained under conditions of controlled temperature (22-24°C) and illumination (12:12-h light-dark cycle starting at 6 A.M.). Rats had ad libitum access to Purina laboratory chow (St. Louis, MO) and tap water. Animals were deprived of food for 24 h but had free access to water until 2 h before the beginning of the experiments. All studies were performed in rats anesthetized by intraperitoneal injection of urethan (1.5 g/kg, Sigma Chemical, St. Louis, MO).

Drugs and treatments. Porcine/rat PYY (p/r PYY) (kindly provided by Dr. J. Rivier, Salk Institute, La Jolla, CA) was dissolved in 0.1% BSA (Sigma Chemical)/saline before intravenous infusion. p/r PYY and p/r PYY3-36 (Peptides Synthesis Core Facility, University of California, Los Angeles, CA) were dissolved in saline before intracisternal injection. The stable TRH analog RX-77368 [pGlu-His-(3,3'-dimethyl)-Pro-NH2; Ferring Pharmaceuticals, Feltham, UK] was diluted in saline before intracisternal injection from aliquots of a stock solution (30 µg/ml in 0.1% BSA and saline, kept at -70°C). The control groups were infused intravenously or injected intracisternally with the corresponding vehicles.

The protein A-Sepharose column-purified IgG from a polyclonal PYY antiserum (CURE 9153) was provided by the Antibody Core Laboratory of CURE: Digestive Diseases Research Center (Los Angeles, CA). This antibody has been used previously for in vivo immunoneutralization to assess endogenous PYY actions (3, 43). By RIA, the PYY antibody has no cross-reactivity with rat or human pancreatic polypeptide (3), but displays a 35% cross-reactivity with p/r PYY3-36 at a dilution of 1:30,000 (Fig. 1) when tested under the same conditions as previously reported (3). Normal rabbit IgG (NRIgG) was used as the control antibody. The anti-PYY IgG and NRIgG used for intracisternal injection were dialyzed against 20 mM phosphate and 110 mM NaCl (pH 7.0) and concentrated using an S-43-70 Spectra/Por stirred cell with 100k MWCO type C ultrafiltration membranes (Spectrum Medical Industries, Los Angeles, CA). IgG concentration was estimated by measuring the optical density at the light wavelength of 280 nm.


View larger version (17K):
[in this window]
[in a new window]
 
Fig. 1.   Characterization of the peptide YY (PYY) polyclonal antibody (CURE 9153) for sensitivity and specificity by liquid phase RIA. The serum was diluted 1:30,000 and 125I-[Tyr1]-PYY1-36 was used as labeled antigen. ID50, half-maximal inhibitory dose. B/F, bound/free.

For intracisternal injection, rats were placed in ear bars of a stereotaxic apparatus, and the atlantooccipital membrane was punctured with a 50-µl Hamilton syringe (Reno, NV). The correctness of needle placement into the cisterna magna was insured by the presence of cerebrospinal fluid in the Hamilton syringe on aspiration before injection of vehicle or peptides.

Experimental protocols and measurement of gastric acid secretion. In urethan-anesthetized rats, the jugular vein was cannulated with a PE-50 catheter (Clay Adams) for intravenous infusion. The esophagus was ligated at the cervical level, and a laparotomy was performed. The pylorus was ligated, and a double-lumen gastric cannula was implanted into the forestomach. After a 30-min stabilizing period, gastric acid secretion was measured every 10 min by flushing the stomach through the double-lumen cannula with two 5-ml boluses of saline at room temperature and one 5-ml bolus of air at the end of each 10-min period. Acid output was determined by titration of the flushed perfusate with 0.01 N NaOH using an autotitrator (TTT titrator, Radiometer, Copenhagen, Denmark). The PYY infusion through the jugular vein (1.08 ml/h) was started 30 min before intracisternal injection of the stable TRH analog RX-77368 (14 pmol/10 µl). Antibodies were administered intravenously (1 ml/kg) or intracisternally (280 µg/20 µl) at 10 min before the start of intravenous PYY infusion (1 nmol · kg-1 · h-1) or intracisternal injection of PYY (2.4 pmol/5 µl) and RX-77368 (1.4 pmol/5 µl). Gastric acid secretions were measured from 20 min before any treatment to 90 min after intracisternal injection of RX-77368. In one experiment, PYY or PYY3-36 (2.4 pmol/5 µl) was injected intracisternally 10 min before intracisternal RX-77368 (14 pmol/5 µl). The net gastric acid output was calculated by subtracting the average basal value of acid output from each postinjection value. Reversal of the PYY intravenous or intracisternal inhibitory effect by PYY antibody was calculated by dividing the difference in acid output for PYY antibody and PYY vs. control antibody and PYY by the difference in acid output for PYY vs. vehicle groups.

Statistical analysis. All results are expressed as means ± SE. Comparisons among multiple groups were performed by one-way ANOVA followed by Duncan's contrast. Comparisons between two groups were performed by Student t-test. P < 0.05 was considered statistically significant.


    RESULTS
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Effect of intravenous PYY on gastric acid secretion stimulated by intracisternal RX-77368. Basal gastric acid secretion was low (0-0.4 µmol/10 min) in urethan-anesthetized rats. In rats intravenously infused with vehicle, the stable TRH analog RX-77368 (14 pmol/rat) injected intracisternally induced a net acid secretion of 58.8 ± 6.7 µmol/90 min. The acid response began at 10 min and reached its peak 20-40 min after intracisternal injection of the TRH analog. PYY (0.25, 0.5, or 1 nmol · kg-1 · h-1) infused intravenously starting at 30 min before intracisternal RX-77368 (14 pmol) dose- dependently inhibited the acid response to intracisternal RX-77368 by 52%, 69%, and 83%, respectively, compared with vehicle-infused control, whereas PYY at 0.125 nmol · kg-1 · h-1 had no significant inhibitory effect (61.7 ± 13.9 µmol/90 min) (Fig. 2). Intravenous PYY infusion (0.125, 0.25, 0.5, or 1 nmol · kg-1 · h-1 for 30 min) did not influence basal gastric acid secretion in urethan-anesthetized rats (data not shown).


View larger version (23K):
[in this window]
[in a new window]
 
Fig. 2.   The inhibitory effect of intravenous PYY infusion on intracisternal RX-77368-induced gastric acid secretion and the reversal of PYY action by intravenous PYY antibody in urethan-anesthetized rats. Intravenous PYY infusion was started 30 min before intracisternal RX-77368, and PYY antibody was injected intravenously 10 min before intravenous infusion of PYY. Each bar represents the mean ± SE of the no. of rats indicated at the base of each bar. * P < 0.05 compared with intravenous 0.1% BSA/saline group. # P < 0.05 compared with 1 nmol · kg-1 · h-1 iv PYY without PYY antibody (Ab) pretreatment group.

Effect of intravenous PYY antibody on intravenous PYY antisecretory action. The PYY antibody injected intravenously (2.25 or 4.5 mg/rat, -10 min) dose-dependently blocked peripheral PYY (1 nmol · kg-1 · h-1 iv)-induced inhibition of the acid response to intracisternal RX-77368 (14 pmol) in urethan-anesthetized rats. PYY antibody at 2.25 or 4.5 mg/rat returned gastric acid output values to 29.5 ± 16.3 and 79.3 ± 5.4 µmol/90 min, respectively (3- and 8-fold increases, respectively, compared with 10.1 ± 5.2 µmol/90 min in rats without antibody pretreatment). PYY antibody at a lower dose (1 mg/rat iv) did not influence the PYY (1 nmol · kg-1 · h-1 iv) inhibitory effect on intracisternal RX-77368-induced gastric acid secretion (14.7 ± 2.0 µmol/90min) (Figs. 2 and 3). PYY antibody alone injected intravenously at 4.5 mg/rat did not influence basal acid secretion in urethan-anesthetized rats (net acid output, 2.7 ± 5.8 µmol/90 min; n = 4).


View larger version (22K):
[in this window]
[in a new window]
 
Fig. 3.   Time course of the blockade of intravenous PYY-induced inhibition on acid response to intracisternal RX-77368 by intravenous PYY antibody. Each point represents the mean ± SE of the no. of rats indicated in parentheses. * P < 0.05 compared with the corresponding value in the PYY antibody (1 mg/rat) group.

Effect of intracisternal PYY and PYY3-36 on gastric acid secretion-induced by intracisternal RX-77368. In the saline-pretreated group (5 µl saline ic, administered at -10 min), the acid response to RX-77368 (14 pmol/5 µl) was 112 ± 28 µmol/90 min (Fig. 4). Pretreatment with intracisternal PYY (2.4 pmol/5 µl) or PYY3-36 (2.4 pmol/5 µl) significantly inhibited the acid response to intracisternal RX-77368 by 80% and 73%, respectively, compared with the intracisternal saline-pretreated group (Fig. 4). PYY (2.4 pmol) injected intracisternally did not influence basal gastric acid secretion (see Fig. 7).


View larger version (22K):
[in this window]
[in a new window]
 
Fig. 4.   Effect of intracisternal injection of PYY1-36 and PYY3-36 on intracisternal RX-77368-induced gastric acid secretion in urethan-anesthetized rats. Each point represents mean ± SE of the no. of rats indicated in parentheses. Inset, the mean ± SE of the integrated net acid output in each group. No. of rats is indicated at the base of each bar. * P < 0.05 compared with intracisternal saline-pretreated group.

Effect of intracisternal PYY antibody on intracisternal PYY antisecretory action. The control antibody (280 µg/20 µl ic) injected 10 min before intracisternal injection of a mixture of PYY (2.4 pmol) and RX-77368 (1.4 pmol) in a volume of 5 µl did not influence the inhibitory effect of intracisternal PYY on RX-77368-induced acid secretion. The net acid output (25.5 ± 15.4 µmol/90min, Fig. 5) was similar to that obtained when the two peptides were injected intracisternally separately (Fig. 4). In contrast, intracisternal PYY antibody pretreatment (280 µg/20 µl, -10 min) reversed the PYY inhibitory effect by 64%, and the net acid output returned to 77.0 ± 13.2 µmol/90min (Fig. 5).


View larger version (24K):
[in this window]
[in a new window]
 
Fig. 5.   PYY antibody injected intracisternally prevents intracisternal PYY-induced inhibition of acid response to intracisternal RX-77368 in urethan-anesthetized rats. Each point represents the mean ± SE of the no. of rats indicated in parentheses. Inset, the mean ± SE of the integrated net acid output in each group. No. of rats is indicated at the base of each bar. * P < 0.05 compared with intracisternal control antibody-pretreated group.

Effect of intracisternal PYY antibody on intravenous PYY antisecretory action. The PYY antibody (280 µg/20 µl) injected intracisternally 10 min before the intravenous infusion of PYY (1 nmol · kg-1 · h-1) reversed the intravenous PYY-induced inhibition of gastric acid secretion stimulated by intracisternal RX-77368 (14 pmol) (Fig. 6). The net acid responses to intracisternal RX-77368 in intracisternal control and PYY antibody-pretreated rats infused intravenously with PYY (1 nmol · kg-1 · h-1) were 4.5 ± 3.5 and 55.3 ± 10.0 µmol/90 min, respectively. This represents a 93.5% reversal of the inhibitory effect of intravenous PYY on the acid response to intracisternal RX-77368 (Fig. 6). PYY antibody (280 µg) or the control antibody (280 µg) injected intracisternally did not significantly influence either the basal gastric acid secretion or the acid response to intracisternal RX-77368 (14 pmol) in urethan-anesthetized rats (Fig. 7).


View larger version (19K):
[in this window]
[in a new window]
 
Fig. 6.   PYY antibody injected intracisternally prevents intravenous PYY-induced inhibition of acid response to intracisternal RX-77368 in urethan-anesthetized rats. Each point represents the mean ± SE of no. of rats indicated in parentheses. * P < 0.05 compared with intracisternal control antibody-pretreated group.



View larger version (14K):
[in this window]
[in a new window]
 
Fig. 7.   Influence of intracisternal injection of PYY peptide (2.4 pmol), PYY antibody (280 µg), and the control antibody (280 µg) on basal or intracisternal RX-77368-induced gastric acid secretion in urethan-anesthetized rats. Each bar represents the mean ± SE of no. of rats indicated at the base of each bar


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

TRH is an endogenous neurotransmitter in the medulla that plays an important physiological role in the vagal regulation of gastric functions (28). Medullary TRH-synthesizing neurons are mainly located in the caudal raphe nuclei and project to innervate the DMN (17, 19, 27). TRH microinjected into the DMN stimulates gastric acid secretion through activating the vagus (13, 21). The intracisternal injection of the stable TRH analog RX-77368 is a well established and widely used tool to induce central vagally mediated stimulation of gastric acid secretion and motility in conscious or anesthetized rats (28). In the present study, PYY infused intravenously dose-dependently inhibited gastric acid secretion induced by intracisternal RX-77368 in urethan-anesthetized rats. This finding provides additional evidence that peripheral PYY is a potent inhibitor of central vagally stimulated gastric acid secretion, as previously reported in other models, such as acid responses to sham feeding (24) and 2-deoxy-glucose (25). The minimal effective dose at which intravenous PYY exerts an antisecretory effect (250 pmol · kg-1 · h-1) is in the range similar to that previously reported (14) to induce physiological concentrations in the circulation. The acid response to intracisternal RX-77368 (14 pmol) mimics the levels of acid secretion stimulated by cold stress (42), which has been shown to be mediated through medullary TRH (11, 42). Based on the well-established demonstration that medullary TRH stimulates vagal efferent activity (22) and plays a physiological role in the cephalic phase of acid secretion (2, 29), whereas PYY is one of the enterogastrones (30), the present findings suggest a possible physiological relevance of the interaction between peripheral PYY and central TRH to regulate gastric acid secretion during digestion.

Although the physiological significance of endogenous PYY and its interactions with other gastrointestinal peptides to regulate gastric secretion after a meal is important to investigate, the present study was focused on the mechanism of peripheral PYY inhibitory action. Growing evidence (8, 26) has revealed the central vagal components that respond to a meal. In particular, Fos immunoreactivity was induced in neurons of the NTS and area postrema after feeding and intraduodenal loading (8, 26, 38). Peripheral injection of PYY has a similar effect (4). Several lines of morphological and functional evidence (7, 12, 18, 23-25) also support the view that the medulla is the action site for peripheral PYY to inhibit gastric and pancreatic functions. To be consistent with the hypothesis that intravenously administered PYY inhibits central TRH-induced gastric acid secretion by acting in the medulla, PYY injected directly into the cisterna magna at lower doses should mimic the inhibitory effect of peripherally infused PYY. Indeed, PYY or PYY3-36 injected intracisternally at 2.4 pmol inhibits intracisternal RX-77368-stimulated acid secretion similarly to intravenous infusion of PYY at 0.5-1 nmol · kg-1 · h-1. PYY1-36 and PYY3-36 are the two molecular forms that are abundant in the blood (9). Both PYY and PYY3-36 (or PYY13-36) exhibit similar affinity to the Y2 receptors (1), and when applied to the DMN in femtomole levels, inhibited DMN neuronal activity (5), as well as TRH-stimulated gastric motility (6). These findings, together with present results showing that PYY and PYY3-36 injected intracisternally are equipotent to inhibit vagally stimulated acid secretion by intracisternal TRH analog, support the view that the medulla is an action site for a low dose of PYY to inhibit vagally stimulated gastric functions through Y2 receptors.

In the absence of available specific Y2 receptor antagonists, to obtain direct evidence that peripheral PYY acts in the medulla to inhibit gastric acid secretion, we used the immunoneutralization method of approach. The PYY antibody CURE 9153 proved to be valuable in evaluating the role of circulatory PYY in intestinal nutrition-induced absorption (3) and inhibition of gastric acid secretion (43) in dogs. This antibody is selective for PYY and has ~35% cross-reactivity with PYY3-36 (present study) but does not cross-react with pancreatic polypeptide (3). The PYY antibody injected intravenously completely blocked intravenous PYY-induced inhibition of the acid response to intracisternal RX-77368, and when injected intracisternally, prevented the inhibitory effect of intracisternal PYY by 64%. This provides biological evidence of its immunoneutralizing potency in rats. The lower amount of PYY antibody that has no peripheral effect abolished the antisecretory effect of intravenously infused PYY by 93.5% when injected into the cisterna magna. To avoid the possibility of serendipitous phenomenon, the same experiment was repeated three times with similar reproducible significant results each time. These findings provide strong evidence that peripherally infused PYY does act in the brain to inhibit intracisternal TRH analog-induced stimulation of gastric secretion. It is most likely that the PYY antibody injected intracisternally neutralized PYY that entered from the circulation into the medulla via the area postrema and part of the NTS, where the blood-brain barrier is deficient (10). The present result is in line with the demonstration that intravenous infusion of PYY at physiological concentrations gains access to PYY binding sites located in portions of the DVC (12). The possibility that the intracisternal-injected PYY antibody reacts with intracisternal-injected RX-77368 to increase acid secretion can be excluded, because intracisternal injection of PYY antibody or control antibody did not influence basal and RX-77368-induced gastric acid secretion.

Intracerebroventricular or intracisternal passive immunization has been used extensively to inhibit central actions of peptide (20, 32). It has been proved by immunohistochemistry that antibody injected intracerebroventricularly penetrated into brain tissues (34) and specifically accumulated by neurons with the antigen protein (31). The vast majority of investigators using this technique made the assumption that the small quantities of antisera or purified antibodies administered into the ventricles inhibit the action of a neuropeptide specifically within the brain and do not gain access to peripheral tissues in substantial quantities. This assumption is based on an understanding of limited transport of large-molecular-weight proteins across the blood-brain barrier (15) and the unlikelihood that antibodies can reach the systemic circulation in significant amounts after intracisternal or intracerebroventricular administration. However, recent studies (33) revealed that small quantities of antisera injected intracerebroventricularly can neutralize peripheral peptides. All three tested antisera injected into the rat cerebroventricle were detected in the systemic circulation within 30 min after intracerebroventricular infusion of 5 µl antiserum (33). However, it is unlikely that similar mechanisms would contribute to the results obtained in the present study. Although 280 µg/rat of purified anti-PYY IgG injected intracisternally almost completely prevented the antisecretory action of intravenous PYY, a 10-fold larger amount (2.25 mg/rat) of the same antibody injected intravenously showed a much weaker effect. To obtain a potency similar to that observed after intracisternal PYY antibody injection, the required dose of intravenous PYY antibody was 4.5 mg, i.e., 16 times larger than the intracisternal effective dose.

Zhao et al. (43) recently reported that intravenous PYY antibody did not prevent intraduodenal fat-induced inhibition of acid secretion in dogs. The results of the present study are not incompatible with the findings of Zhao et al. (43). Our observations are consistent with other previous studies (24, 25) showing that PYY is more potent in inhibiting the cephalic phase of acid secretion, whereas in the study of Zhao et al.(43) there was no cephalic phase involved, as the acid was stimulated by intragastric peptone, which mimics a gastric phase of acid secretion.

In summary, PYY was more potent in inhibiting intracisternal TRH analog-induced stimulation of gastric acid secretion in urethan-anesthetized rats when administered intracisternally rather than intravenously. PYY antibody was more potent in reversing the antisecretory action of intravenously infused PYY when injected intracisternally rather than intravenously. In addition, intracisternal injection of PYY3-36 mimics the antisecretory effect of intracisternal PYY. These findings, together with previous observations (4, 5, 7, 12, 18, 23-25), strongly support the view that peripheral PYY-induced inhibition of vagally stimulated gastric functions involves a Y2-mediated central mechanism, possibly at a medullary site.


    ACKNOWLEDGEMENTS

We thank Dr. J. Rivier (Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, CA) for supplying rat PYY, Dr. J. Reeve, Jr. (Peptides Synthesis Core Facility, University of California, Los Angeles, CA) for supplying porcine/rat PYY and porcine/rat PYY3-36, and Paul Kirsch for assistance in manuscript preparation.


    FOOTNOTES

dagger Deceased 14 June 2000.

This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grants DK-30110 (Y. Taché), DK-50255 (H. Yang), and DK-41301 (Animal Core, Antibody Core, and Peptides Core).

Address for reprint requests and other correspondence: H. Yang, CURE: Digestive Diseases Research Center, Veterans Affairs Greater Los Angeles Healthcare System, Bldg 115, Rm. 203, 11301 Wilshire Blvd., Los Angeles, CA 90073 (E-mail: hoyang{at}ucla.edu).

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Received 2 February 2000; accepted in final form 10 April 2000.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Balasubramaniam, AA. Neuropeptide Y family of hormones: receptor subtypes and antagonists. Peptides 18: 445-457, 1997[ISI][Medline].

2.   Barrachina, MD, Wu SV, and Taché Y. Central TRH receptors are involved in the gastric secretory response to sham-feeding in rats (Abstract). Gastroenterology 112: A1130, 1997[ISI].

3.   Bilchik, AJ, Hines OJ, Ashley SW, Adrian TE, Walsh J, Wong H, Liu CD, Zinner MJ, and McFadden DW. Peptide YY immunoneutralization inhibits meal-induced absorption in vivo. Surgery 116: 1153-1157, 1994[ISI][Medline].

4.   Bonaz, B, Taylor I, and Taché Y. Peripheral peptide YY induces c-fos-like immunoreactivity in the rat brain. Neurosci Lett 163: 77-80, 1993[ISI][Medline].

5.   Chen, CH, and Rogers RC. Peptide YY and the Y2 agonist PYY-(13-36) inhibit neurons of the dorsal motor nucleus of the vagus. Am J Physiol Regulatory Integrative Comp Physiol 273: R213-R218, 1997[Abstract/Free Full Text].

6.   Chen, CH, Stephens RLJ, and Rogers RC. PYY and NPY: control of gastric motility via action on Y1 and Y2 receptors in the DVC. Neurogastroenterol Motil 9: 109-116, 1997[ISI][Medline].

7.   Dumont, Y, Fournier A, St-Pierre S, and Quirion R. Autoradiographic distribution of [125I]Leu31,Pro34 PYY and [125I]PYY3-36 binding sites in the rat brain evaluated with two newly developed Y1 and Y2 receptor radioligands. Synapse 22: 139-158, 1996[ISI][Medline].

8.   Emond, MH, and Weingarten HP. Fos-like immunoreactivity in vagal and hypoglossal nuclei in different feeding states: a quantitative study. Physiol Behav 58: 459-465, 1995[ISI][Medline].

9.   Grandt, D, Schimiczek M, Beglinger C, Layer P, Goebell H, Eysselein VE, and Reeve JRJ Two molecular forms of peptide YY (PYY) are abundant in human blood: characterization of a radioimmunoassay recognizing PYY 1-36 and PYY 3-36. Regul Pept 51: 151-159, 1994[ISI][Medline].

10.   Gross, PM, Wall KM, Pang JJ, Shaver SW, and Wainman DS. Microvascular specializations promoting rapid interstitial solute dispersion in nucleus tractus solitarius. Am J Physiol Regulatory Integrative Comp Physiol 259: R1131-R1138, 1990[Abstract/Free Full Text].

11.   Hernandez, DE, Arredondo ME, Xue BG, and Jennes L. Evidence for a role of brain thyrotropin-releasing hormone (TRH) on stress gastric lesion formation in rats. Brain Res Bull 24: 693-695, 1990[ISI][Medline].

12.   Hernandez, EJ, Whitcomb DC, Vigna SR, and Taylor IL. Saturable binding of circulating peptide YY in the dorsal vagal complex of rats. Am J Physiol Gastrointest Liver Physiol 266: G511-G516, 1994[Abstract/Free Full Text].

13.   Ishikawa, T, Yang H, and Taché Y. Medullary sites of action of the TRH analog, RX-77368, for stimulation of gastric acid secretion in the rat. Gastroenterology 95: 1470-1476, 1988[ISI][Medline].

14.   Jin, H, Cai L, Lee K, Chang TM, Li P, Wagner D, and Chey WY. A physiological role of peptide YY on exocrine pancreatic secretion in rats. Gastroenterology 105: 208-215, 1993[ISI][Medline].

15.   Johansson, BB. The physiology of the blood-brain barrier. Adv Exp Med Biol 274: 25-39, 1990[Medline].

16.   Laughton, WB, and Powley TL. Localization of efferent function in the dorsal motor nucleus of the vagus. Am J Physiol Regulatory Integrative Comp Physiol 252: R13-R25, 1987[Abstract/Free Full Text].

17.   Liao, N, Bulant M, Nicolas P, Vaudry H, and Pelletier G. Immunoelectron microscopic localization of thyrotropin-releasing hormone (TRH) precursor in the rat raphe nuclei. Peptides 11: 397-400, 1990[ISI][Medline].

18.   Lynch, DR, Walker MW, Miller RJ, and Snyder SH. Neuropeptide Y receptor binding sites in rat brain: differential autoradiographic localizations with 125I-peptide YY and 125I-neuropeptide Y imply receptor heterogeneity. J Neurosci 9: 2607-2619, 1989[Abstract].

19.   Lynn, RB, Kreider MS, and Miselis RR. Thyrotropin-releasing hormone-immunoreactive projections to the dorsal motor nucleus and the nucleus of the solitary tract of the rat. J Comp Neurol 311: 271-288, 1991[ISI][Medline].

20.   Niida, H, Takeuchi K, and Okabe S. Role of thyrotropin-releasing hormone in acid secretory response induced by lowering of body temperature in the rat. Eur J Pharmacol 198: 137-142, 1991[ISI][Medline].

21.   Okuma, Y, Osumi Y, Ishikawa T, and Mitsuma T. Enhancement of gastric acid output and mucosal blood flow by tripeptide thyrotropin releasing hormone microinjected into the dorsal motor nucleus of the vagus in rats. Jpn J Pharmacol 43: 173-178, 1987[ISI][Medline].

22.   O-Lee, TJ, Wei JY, and Taché Y. Intracisternal TRH and RX-77368 potently activate gastric vagal efferent discharge in rats. Peptides 18: 213-219, 1997[ISI][Medline].

23.   Pappas, TN, Debas HT, Chang AM, and Taylor IL. Peptide YY release by fatty acids is sufficient to inhibit gastric emptying in dogs. Gastroenterology 91: 1386-1389, 1986[ISI][Medline].

24.   Pappas, TN, Debas HT, and Taylor IL. Enterogastrone-like effect of peptide YY is vagally mediated in the dog. J Clin Invest 77: 49-53, 1986[ISI][Medline].

25.   Putnam, WS, Liddle RA, and Williams JA. Inhibitory regulation of rat exocrine pancreas by peptide YY and pancreatic polypeptide. Am J Physiol Gastrointest Liver Physiol 256: G698-G703, 1989[Abstract/Free Full Text].

26.   Rinaman, L, Baker EA, Hoffman GE, Stricker EM, and Verbalis JG. Medullary c-Fos activation in rats after ingestion of a satiating meal. Am J Physiol Regulatory Integrative Comp Physiol 275: R262-R268, 1998[Abstract/Free Full Text].

27.   Segerson, TP, Hoefler H, Childers H, Wolfe HJ, Wu P, Jackson IM, and Lechan RM. Localization of thyrotropin-releasing hormone prohormone messenger ribonucleic acid in rat brain in situ hybridization. Endocrinology 121: 98-107, 1987[Abstract].

28.   Taché, Y, and Yang H. Role of medullary TRH in the vagal regulation of gastric function. In: Innervation of the Gut: Pathophysiological Implications, edited by Wingate DL, and Butkd TF.. Boca Raton, FL: CRC, 1994, p. 67-80.

29.   Taché, Y, Yang H, and Yoneda M. Vagal regulation of gastric function involves thyrotropin-releasing hormone in the medullary raphe nuclei and dorsal vagal complex. Digestion 54: 65-72, 1993[ISI][Medline].

30.   Taylor, IL. Pancreatic polypeptide family: pancreatic polypeptide, neuropeptide Y, and peptide YY. In: Handbook of Physiology. The Gastrointestinal System. Neural and Endocrine Biology. Bethesda, MD: Am. Physiol. Soc, 1989, sect. 6, vol. II, chapt. 21, p. 475-544.

31.   Thomas, LB, Book AA, and Schweitzer JB. Immunohistochemical detection of a monoclonal antibody directed against the NGF receptor in basal forebrain neurons following intraventricular injection. J Neurosci Methods 37: 37-45, 1991[ISI][Medline].

32.   Turnbull, AV, and Rivier CL. Intracerebroventricular passive immunization. I The effect of intracerebroventricular administration of an antiserum to tumor necrosis factor-alpha on the plasma adrenocorticotropin response to lipopolysaccharide in rats. Endocrinology 139: 119-127, 1998[Abstract/Free Full Text].

33.   Turnbull, AV, and Rivier CL. Intracerebroventricular passive immunization. II. Intracerebroventricular infusion of neuropeptide antisera can inhibit neuropeptide signaling in peripheral tissues. Endocrinology 139: 128-136, 1998[Abstract/Free Full Text].

34.   Van der Zee, CE, Fawcett J, and Diamond J. Antibody to NGF inhibits collateral sprouting of septohippocampal fibers following entorhinal cortex lesion in adult rats. J Comp Neurol 326: 91-100, 1992[ISI][Medline].

35.   Van der Zee, CE, Lourenssen S, Stanisz J, and Diamond J. NGF deprivation of adult rat brain results in cholinergic hypofunction and selective impairments in spatial learning. Eur J Neurosci 7: 160-168, 1995[ISI][Medline].

36.   Van Oers, JW, and Tilders FJ. Antibodies in passive immunization studies: characteristics and consequences. Endocrinology 128: 496-503, 1991[Abstract].

37.   Van Oers, JW, van Bree C, White A, and Tilders FJ. Antibodies to neuropeptides as alternatives for peptide receptor antagonists in studies on the physiological actions of neuropeptides. Prog Brain Res 92: 225-234, 1992[ISI][Medline].

38.   Wang, L, Cardin S, Mart Tach, and Lloyd KC. Duodenal loading with glucose induces Fos expression in rat brain: selective blockade by devazepide. Am J Physiol Regulatory Integrative Comp Physiol 277: R667-R674, 1999[Abstract/Free Full Text].

39.   Yang, H, Li WP, Reeve JRJ, Rivier J, and Taché Y. PYY-preferring receptor in the dorsal vagal complex and its involvement in PYY stimulation of gastric acid secretion in rats. Br J Pharmacol 123: 1549-1554, 1998[Abstract].

40.   Yang, H, Ohning GV, and Taché Y. TRH in dorsal vagal complex mediates acid response to excitation of raphe pallidus neurons in rats. Am J Physiol Gastrointest Liver Physiol 265: G880-G886, 1993[Abstract/Free Full Text].

41.   Yang, H, Wong H, Wu V, Walsh JH, and Taché Y. Somatostatin monoclonal antibody immunoneutralization increases gastrin and gastric acid secretion in urethane-anesthetized rats. Gastroenterology 99: 659-665, 1990[ISI][Medline].

42.   Yang, H, Wu SV, Ishikawa T, and Taché Y. Cold exposure elevates thyrotropin-releasing hormone gene expression in medullary raphe nuclei: relationship with vagally mediated gastric erosions. Neuroscience 61: 655-663, 1994[ISI][Medline].

43.   Zhao, XT, Walsh JH, Wong H, Wang L, and Lin HC. Intestinal fat-induced inhibition of meal-stimulated gastric acid secretion depends on CCK but not peptide YY. Am J Physiol Gastrointest Liver Physiol 276: G550-G555, 1999[Abstract/Free Full Text].


Am J Physiol Gastrointest Liver Physiol 279(3):G575-G581
0193-1857/00 $5.00 Copyright © 2000 the American Physiological Society