Central somatostatin prevents vagal efferent nerve excitation produced by TRH but not by 2-deoxy-D-glucose.
Thyrotropin-releasing hormone (TRH) administered intracerebroventricularly and intravenous injection of 2-deoxy-D-glucose (2-DG) stimulate pancreatic exocrine secretion via vagal efferent nerve excitation. We examined whether centrally administered somatostatin would inhibit pancreatic exocrine secretion that was stimulated by vagal efferent nerve excitation in conscious rats. The animals were prepared with cannulas draining bile and pancreatic juice separately and with a duodenal cannula, a cerebroventricular cannula, and a right jugular vein cannula. Intracerebroventricular injection of somatostatin (0.4 or 4 nmol) significantly inhibited pancreatic secretion induced by TRH (50 or 500 pmol) in a dose-dependent manner. Intravenous injection of somatostatin had no effect on pancreatic secretion stimulated by TRH. On the other hand, somatostatin injected centrally did not affect pancreatic secretion induced by 2-DG (75 mg/kg) or basal secretion. These results suggest that TRH and 2-DG stimulate vagal efferent nerves via distinct mechanisms and that central somatostatin selectively inhibits excitation of the vagus induced by peptidergic (TRH) stimulation.
Masuda
M
M
Department of Clinical Physiology, Tokyo Metropolitan Institute of Gerontology, Japan.
Kanai
S
S
Miyasaka
K
K
D000818:Animals; D001921:Brain / Q000502:physiology*; D003847:Deoxyglucose / Q000494:pharmacology*; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology; D006727:Hormone Antagonists / Q000494:pharmacology*; D007276:Injections, Intraventricular; D008297:Male; D010179:Pancreas / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000494:pharmacology*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014630:Vagus Nerve / Q000187:drug effects* / Q000502:physiology
D006727:Hormone Antagonists; D013004:Somatostatin; D013973:Thyrotropin-Releasing Hormone; D003847:Deoxyglucose