Thyrotropin-releasing hormone (TRH) may play a physiological role as a neurotransmitter or a neuromodulator in addition ot its hormonal role. It is distributee not only in the hypothalamus but also in extrahypothalamic tissues including pancreas
and
gastrointestinal tissue. but limited studies suggest that TRH can stimulate pancreatic secretion and a paucity in information and contrtoversy still remain. Therefore, in treh resent study, the mechanism of the intracerebroventricular (i. c. v.)
TRH-induced pancreatic exocrine stimulation was investigated in trat pancreas in relation to central vagal factor, gastric acid factor, duodenal factor and local vagal reflex affecting secretory mechanism of exocrine pancreas. I. . v. injection
of
TRH
(3 ㎍) stimulated the amylase and protein secretion. The effect reached maximum at 30 minutes and returned to basal level at 90 minutes after a dministration. But pancreatico-biliary flow was little affected. These effects of TRH were blocked by
bilateral vagotomy and posterior truncal vagotomy. but not by anterior truncal vagotomy. Procedures of the pylorus ligation and the resection of pyloroduodenal junction also blocked TRH-induced pancreatic secretion. However. treatment with
cimetidine,
L-364, 718 (a selective CCK antagonist) or reconnection of pyloroduodenal junction had small or no effect on TRH-induced pancreatic secretion.
These results suggest that the central TRH stimulates the pancreatic exocrine secretion, which is mediated mainly via vagus, especially posterior vagal trunk.
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