Intracerebral adrenoceptor agonists influence rat duodenal mucosal
bicarbonate secretion.
Larson, Gerald M., Gunilla Jedstedt, Olof Nylander, Gunnar
Flemstr[diaeresis]om.
Department of Physiology and Medical Biophysics, Uppsala,
University, BMC Box 572, S-751 23 Uppsala, Sweden; and the Department
of Surgery, University of Louisville School of Medicine, Louisville,
Kentucky 40292
APStracts 3:0108G, 1996.
We have studied the effects of intracerebral administration of
selective [alpha]-adrenergic agonists on duodenal bicarbonate
secretion. Duodenum free of Brunner's glands was cannulated in situ
in anesthetized rats and bicarbonate secretion into the luminal
reperfusate was continuously titrated by pH stat. Infusion of the
[alpha]1-selective adrenoceptor agonist, phenylephrine (1,000-2,500
[mu]g x kg-1 x h-1), into a lateral brain ventricle increased
(p<0.01) duodenal bicarbonate secretion. Pretreatment with
prazosin, an [alpha]1-antagonist, significantly (p<0.01) reduced
the stimulatory effect when infused into the lateral ventricle (30
[mu]g x kg-1 x h-1), but not when administered intravenously (1,000
[mu]g x kg-1 x h-1). Hexamethonium (10 mg x kg-1 x h-1,
intravenously) abolished stimulation whereas cervical vagotomy,
epidural blockade, and naloxone each were without effect.
Vasopressin, vasopressin antagonists and oxytocin did not affect
basal secretion. Intracerebroventricular administration of the
[alpha]2-adrenoceptor agonist, clonidine (1,000[mu]g x kg-1 x h-1),
in contrast to [alpha]1-receptor activation, decreased (p<0.01)
the secretion. Thus central nervous adrenoceptors influence duodenal
mucosal bicarbonate secretion, and [alpha]1-adrenoceptor stimulation
may provide protection against luminal acid. This potent stimulation
was not mediated by the vagal nerves, spinal cord pathways, nor the
release of [beta]-endorphin but involves nicotinic, possibly enteric
nervous transmission.
Received 14 August 1995; accepted in final form 7 May 1996.
APS Manuscript Number G354-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96