Adrenoceptor involvement in the cardiovascular responses to B-HT 920 in sinoaortic denervated rats.
1. A study was made relating the involvement of alpha-adrenoceptors in the cardiovascular responses to intracerebroventricular (i.c.v.) injection of B-HT 920, a clonidine-type drug, in conscious sham-operated and sinoaortic-denervated rats. 2. Wistar rats were used, 7 days after the sham operation or sinoaortic denervation. For i.c.v. injection of drugs, a guide cannula had been previously implanted in the left lateral ventricle. 3. In sham-operated rats, cardiovascular responses to B-HT 920 (10-60 microg) were increased blood pressure and bradycardia; but, in sinoaortic-denervated rats, after the pressor response, a decrease in blood pressure also was seen. The responses to this agent were greater in sinoaortic-denervated rats than in sham-operated animals. Treatment with the alpha2-adrenoceptor antagonist yohimbine (30 microg), the imidazoline receptor antagonist idazoxan (15 microg) and the alpha1A-adrenoceptor antagonist 5-methylurapidil (15 microg) blocked the responses to B-HT 920 (30 microg). The alpha1-adrenoceptor antagonist prazosin (15 microg) and the alpha1B-adrenoceptor antagonist chloroethylclonidine (100 microg) did not modify the responses to agonist. 4. Sinoaortic denervation enhances the cardiovascular responses to B-HT 920. Moreover, the effects of i.c.v. administration of B-HT 920 could be mediated by several types of brain receptors: imidazoline receptors and alpha1A- and alpha2-adrenoceptors.
Ricci
D
D
Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
Taira
C A
CA
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D003714:Denervation; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D011311:Pressoreceptors / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D001381:Azepines; D011941:Receptors, Adrenergic; C024763:talipexole