Central alpha 1- and alpha 2-adrenoceptors and brain cholinergic stimulation in sinoaortic denervated rats.
The central alpha-adrenoceptor role in cardiovascular responses to intracerebroventricular (i.c.v.) injection of neostigmine, a tertiary anticholinesterase, was studied in conscious sham-operated and sinoaortic-denervated rats. Neostigmine (0.1-1 micrograms i.c.v.) showed dose-dependent pressor and bradycardiac effects in vehicle-pretreated sham-operated rats but only an increased pressor effect in sinoaortic-denervated animals. The pretreatment with the catecholaminergic neurotoxin, 6-hydroxydopamine (250 micrograms i.c.v.), given 72 h previous to the corresponding operation, blunted the cardiovascular effects of neostigmine in both groups of rats. Prazosin (10 and 30 micrograms i.c.v.), an alpha 1-adrenoceptor antagonist, prevented the pressor response to neostigmine (0.3 micrograms i.c.v.) in sham-operated and sinoaortic-denervated rats. Yohimbine, a alpha 2-adrenoceptor antagonist (10 and 30 micrograms i.c.v.), only prevented the bradycardia induced by neostigmine (0.3 micrograms i.c.v.) in the sham-operated rats. 6-Hydroxydopamine pretreatment lowered the norepinephrine content in hypothalamus, midbrain, medulla oblongata and spinal cord, but did not modify it in the pons, in sham-operated rats and sinoaortic-denervated animals. The present results suggested that brain alpha 1-adrenoceptors would mediate the pressor response to neostigmine (i.c.v.) in sham-operated and sinoaortic-denervated rats and central alpha 2-adrenoceptors mediate the bradycardia in sham-operated rats. This work lends support to the view that cardiovascular responses to brain cholinergic stimulation in sham-operated and sinoaortic-denervated rats could be mediated by a central catecholaminergic activation.
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Cátedra de Farmacología, Facultad de Farmacia y Bioquímica, UBA, Argentina.
Enero
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D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000502:physiology*; D001923:Brain Chemistry / Q000187:drug effects; D003714:Denervation; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009388:Neostigmine / Q000008:administration & dosage / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects*; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects*; D012849:Sinoatrial Node / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine; D009388:Neostigmine; D016627:Oxidopamine; D009638:Norepinephrine; D011224:Prazosin