Ja. Terron et al., ROLE OF ALPHA(1)-ADRENOCEPTORS IN THE REDUCTION OF EXTERNAL CAROTID BLOOD-FLOW INDUCED BY BUSPIRONE AND IPSAPIRONE IN THE DOG, Life sciences, 58(1), 1995, pp. 63-73
Citations number
28
Categorie Soggetti
Biology,"Medicine, Research & Experimental","Pharmacology & Pharmacy
The effects of the 5-HT1A receptor agonists with anxiolytic properties
, buspirone and ipsapirone, in the external carotid bed of anaesthetiz
ed dogs were analyzed. Since these agonists produce several vascular e
ffects via activation of both 5-HT receptors and alpha(1)-adrenoceptor
s, their effects were compared with those elicited by the 5-HT agonist
, quipazine, and the alpha(1)-adrenoceptor agonist, methoxamine. 1-Min
intracarotid (i.c.) infusions of buspirone (300 mu g/min), ipsapirone
(40 mu g/min), quipazine (300 mu g/min) and methoxamine (15 mu g/min)
produced consistent decreases in external carotid blood flow (ECBF);
since these changes in blood flow were not accompanied by modification
s in systemic blood pressure, the agonists produced parallel increases
in external carotid resistance. After interruption of the sympathetic
tone by bilateral cervical vagosympathectomy, the vasoconstrictor res
ponses to all the agonists remained unaffected. The intravenous (i.v.)
administration of the nonselective 5-HT1-like receptor antagonist, me
thiothepin (1-100 mu g/kg), potently and dose-dependently antagonized
buspirone-, ipsapirone- and quipazine-induced vasoconstriction; methio
thepin similarly antagonized the vasoconstrictor responses to methoxam
ine. Interestingly, the alpha(1)-adrenoceptor antagonist, prazosin (1-
100 mu g/kg, i.v.), also antagonized the vasoconstrictor responses to
buspirone, ipsapirone and methoxamine in a dose-dependent manner. Fina
lly, buspirone (300 mu g/min, i.c.) and ipsapirone (40 mu g/min, i.c.)
did not modify the responses to noradrenaline (10 mu g/min, i.c.) or
tyramine (100 mu g/min, i.c.). It is concluded that canine external ca
rotid vasoconstriction induced by buspirone and ipsapirone is mainly m
ediated by activation of alpha(1)-adrenoceptors located in vascular sm
ooth muscle, These data further highlight the ability of the above anx
iolytics to produce significant vascular effects under in vivo conditi
ons.