D. Ricci et Ca. Taira, ADRENOCEPTOR INVOLVEMENT IN THE CARDIOVASCULAR-RESPONSES TO B-HT 920 IN SINOAORTIC DENERVATED RATS, General pharmacology, 32(1), 1999, pp. 29-34
1. A study was made relating the involvement of alpha-adrenoceptors in
the cardiovascular responses to intracerebroventricular (ICV) injecti
on of B-HT 920, a clonidine-type drug, in conscious sham-operated and
sinoaortic-denervated rats. 2. Wister rats were used, 7 days after the
sham operation or sinoaortic denervation. For ICV injection of drugs,
a guide cannula had been previously implanted in the left lateral ven
tricle. 3. In sham operated rats, cardiovascular responses to B-HT 920
(10-60 mu g) were increased blood pressure and bradycardia; but, in s
inoaortic-denervated rats, after the presser response, a decrease in b
lood pressure also was seen. The responses to this agent were greater
in sinoaortic-denervated rats than in sham-operated animals. Treatment
with the alpha(2)-adrenoceptor antagonist yohimbine (30 mu g), the im
idazoline receptor antagonist idazoxan (15 mu g) and the alpha(1A)-adr
enoceptor antagonist 5-methylurapidil (15 pg) blocked the responses to
B-HT 920 (30 mu g). The alpha(1)-adrenoceptor antagonist prazosin (15
mu g) and the alpha(1B)-adrenoceptor antagonist chloroethylclonidine
(100 mu g) did not modify the responses to agonist. 4. Sinoaortic dene
rvation enhances the cardiovascular responses to B-HT 920. Moreover, t
he effects of ICV administration of B-HT 920 could be mediated by seve
ral types of brain receptors: imidazoline receptors and alpha(1A)- and
alpha(2)-adrenoceptors. (C) 1998 Elsevier Science Inc.