Regulation of rat ileal water absorption by central alpha 2 adrenergic receptors.
This study examined the role of central adrenergic receptors in the regulation of water absorption by the rat ileum. Clonidine, an alpha 2-adrenergic receptor agonist, increased water absorption in vivo following intracerebroventricular but not intravenous injection. Intracerebroventricular injection of prazosin, an alpha 1-adrenergic receptor antagonist, did not alter basal water absorption. Prazosin did not prevent the clonidine effect. In contrast, the alpha 2-adrenergic receptor antagonist, yohimbine, reduced basal absorption and prevented the intracerebroventricular clonidine effect. Treatment with reserpine reduced ileal norepinephrine content by 98%, reduced basal water absorption consistent with a loss of sympathetic outflow to the mucosa, but did not prevent the increase in water absorption due to intracerebroventricular clonidine. These results suggest that central alpha 2 receptors regulate water absorption by the rat ileum. The clonidine-induced increase in water absorption is not mediated by the sympathetic nerves innervating the intestine.
Fogel
R
R
Department of Medicine, University of Louisville, Kentucky 40292.
Kong
T H
TH
Dong
W H
WH
Pfeiffer
M
M
Michelson
G
G
D000042:Absorption; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000502:physiology*; D003000:Clonidine / Q000494:pharmacology*; D007082:Ileum / Q000378:metabolism*; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012110:Reserpine / Q000494:pharmacology; D013562:Sympathectomy; D014867:Water / Q000493:pharmacokinetics*
D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D014867:Water; D012110:Reserpine; D003000:Clonidine