ISSN:
1432-1912
Keywords:
α-Adrenoceptors
;
Baroreflex
;
Clonidine
;
Noradrenaline
;
Sympathetic tone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Microinjection of noradrenaline and clonidine into lateral medullary pressor area (LMPA) of chloralose anaesthetized cats produced dose dependent decrease in blood pressure without affecting heart rate, while phenylephrine did not elicit any cardiovascular response. Selectiveα 2-adrenoceptor, antagonists idazoxan and piperoxan, microinjected locally, blocked the effects of the agonists but prazosin and phenoxybenzamine, which are relatively selective forα 1-adrenoceptors, failed to do so. Clonidine did not elicit any response in guanethidine pretreated cats but noradrenaline microinjected into LMPA of these animals induced a pressor response which was blocked by prazosin pretreatment. It is concluded that catecholaminergic fibres impinging upon this are inhibit the activity of the inhibitory second order baroreceptor neurone by activatingα 1-adrenoceptors whileα 2-adrenoceptors situated presynaptically on these inhibitory catecholaminergic nerve terminals are responsible for the manifestation of the hypotensive effect of clonidine and exogenously administered noradrenaline.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00572428
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