Pancreatic polypeptide microinjection into the dorsal motor nucleus inhibits pancreatic secretion in rats.
OBJECTIVE
Pancreatic polypeptide (PP), a hormone released from the pancreas, inhibits pancreatic secretion in vivo but not in vitro, suggesting that the inhibitory action of PP on pancreatic secretion is indirect. Circulating PP in physiological concentrations binds to specific receptors in the dorsal vagal complex in the brainstem. Therefore, the hypothesis of this study was that PP acts centrally and inhibits pancreatic secretion by modulating vagal tone.


METHODS
The effects of microinjection of PP into the dorsal motor nucleus on 2-deoxy-D-glucose-stimulated and cholecystokinin octapeptide (CCK-8)-stimulated pancreatic secretion were examined in urethane-anesthetized rats.


RESULTS
Microinjection of PP to the dorsal motor nucleus but not brainstem sites outside it inhibited 2-deoxy-D-glucose-stimulated pancreatic flow and protein output. CCK-8-stimulated pancreatic protein output was inhibited by PP in the dorsal motor nucleus in dose-dependent and site-specific manners. The inhibitory effect of PP on CCK-8-stimulated protein output was eliminated by vagotomy.


CONCLUSIONS
The results suggest that PP acts in the dorsal motor nucleus to modulate vagal tone on the pancreas, thereby inhibiting pancreatic secretion. This study shows for the first time that the dorsal motor nucleus is involved in central feedback inhibition of the exocrine pancreas.
Okumura
T
T
Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA.
Pappas
T N
TN
Taylor
I L
IL
D000704:Analysis of Variance; D000818:Animals; D001933:Brain Stem; D002766:Cholecystokinin / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D005246:Feedback; D008297:Male; D008845:Microinjections; D009046:Motor Neurons; D010179:Pancreas / Q000187:drug effects* / Q000378:metabolism; D010191:Pancreatic Polypeptide / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014628:Vagotomy; D014630:Vagus Nerve
D010191:Pancreatic Polypeptide; D002766:Cholecystokinin; D003847:Deoxyglucose