The alpha 1-blocker dapiprazole inhibits diuresis but not drinking and feeding induced by U-50,488H.
To further explore the interaction between opiates and catecholamines in the control of water balance, we studied the effects of the alpha 1-adrenoceptor antagonist dapiprazole on the modifications in drinking and diuresis produced by U-50,488H (a selective kappa-opiate agonist), morphine, naloxone, and amphetamine in rats. Because animals were maintained in a free-feeding paradigm and water intake is also controlled by feeding (prandial drinking), food intake was also measured. At doses administered (3-6 mg/kg, IP), dapiprazole had no effect on basal food and water intake or on diuresis. Nor did it modify changes in feeding and drinking produced by U-50,488H, morphine, naloxone, and amphetamine. It did, however, antagonize the diuretic effect of both U-50,488H and amphetamine. In addition, suppression of diuresis was obtained by combining doses of dapiprazole and morphine or naloxone that were devoid of antidiuretic effects when administered independently. A further experiment showed that diuresis produced by water load was also prevented by dapiprazole. alpha 1-Adrenoceptors thus appear to play a role in the regulation of water balance in a condition of free access to water, inhibiting diuresis without affecting drinking.
Institute of Medical Pharmacology, University of Rome La Sapienza, Italy.
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Nencini
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Valeri
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Pimpinella
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000661:Amphetamine / Q000494:pharmacology; D000700:Analgesics / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000818:Animals; D004231:Diuresis / Q000187:drug effects*; D004327:Drinking Behavior / Q000187:drug effects*; D005247:Feeding Behavior / Q000187:drug effects*; D008297:Male; D010879:Piperazines; D011759:Pyrrolidines / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014230:Triazoles / Q000494:pharmacology*; D014554:Urination; D014882:Water-Electrolyte Balance / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D000700:Analgesics; D010879:Piperazines; D011759:Pyrrolidines; D014230:Triazoles; C035289:dapiprazole; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000661:Amphetamine