The nucleus raphe obscurus controls pancreatic hormone secretion in
the rat.
Krowicki, Zbigniew K., and Pamela J. Hornby.
Department of Pharmacology and Experimental Therapeutics, Louisiana
State University Medical Center, New Orleans, Louisiana 70112
APStracts 2:0021E, 1995.
Until recently, the dorsal vagal complex (DVC) was considered as the
only brainstem regulatory center for the vagal control of the
endocrine pancreas. Since the nucleus raphe obscurus (NRO) maintains
anatomical connections via the DVC to the pancreas, a functional
significance of these findings was investigated in the present study.
Kainic acid and vehicle were microinjected into the right DVC and the
NRO of alpha-chloralose-anesthetized rats and plasma concentrations
of rat insulin, glucagon, and glucose were determined before and 5,
15, 30, and 60 min after injections. Chemical stimulation of neurons
in the DVC by kainic acid at a dose of 200 pmol evoked increases in
concentrations of insulin, with a peak at 15 min, and glucagon, with
a peak at 30 min. Microinjection of kainic acid into the NRO at a
dose of 200 pmol but not at a dose of 20 pmol, produced increases in
plasma concentrations of insulin, with a peak at 30 min, and
glucagon, with a peak at 60 min. Plasma glucose levels upon
microinjection of kainic acid into the NRO at a dose of 20 pmol were
decreased, whereas no changes upon microinjection of kainic acid at a
dose of 200 pmol were observed. The effects of kainic acid on insulin
and glucagon secretion in the NRO were abolished by bilateral
vagotomy. The study demonstrates for the first time that the NRO can
contribute to vagal control of pancreatic endocrine function,
although the exact circuitry and neurotransmitters involved in this
response remain unknown.
Received 25 July 1994; accepted in final form 2 February 1995.
APS Manuscript Number E289-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.