Evidence for functional separation of alpha-1 and alpha-2 noradrenaline receptors by pre-synaptic terminal re-uptake mechanisms.
Information transfer within the central nervous system is predominantly chemical in nature, and occurs both through synaptic specialisations and non-specific diffuse release. The localisation and description of receptors for these two types of neurotransmission is currently a contentious issue. In the present study, the noradrenaline reuptake inhibitor cocaine has been shown to overcome the inhibitory effects of idazoxan, a selective alpha-2 receptor antagonist, but not phentolamine, a non-selective alpha receptor antagonist, on eating following injection of noradrenaline into the rat hypothalamic paraventricular nucleus. Similarly, lesion by 6-hydroxydopamine of noradrenaline terminals in the paraventricular nucleus also reduced the efficacy of idazoxan in blocking eating induced by noradrenaline. These data confirm that postsynaptic alpha-2 receptors are involved in the feeding response to exogenous noradrenaline, but in addition, when taken in conjunction with previously published data, are used to suggest a differential distribution of NA receptors within the hypothalamic paraventricular nucleus. It is proposed that the alpha-2 subtype may be extrasynaptic, the alpha-1 subtype intrasynaptic.
Psychological Laboratory, University of St. Andrews, Fife, UK.
A J
AJ
Clark
S P
SP
Butcher
P
P
Winn
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D004435:Eating / Q000187:drug effects; D006892:Hydroxydopamines / Q000494:pharmacology; D019329:Idazoxan; D066298:In Vitro Techniques; D008297:Male; D008845:Microinjections; D009411:Nerve Endings / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology*; D016627:Oxidopamine; D010286:Paraventricular Hypothalamic Nucleus / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects* / Q000378:metabolism
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D006892:Hydroxydopamines; D011942:Receptors, Adrenergic, alpha; D016627:Oxidopamine; D003042:Cocaine; D009638:Norepinephrine; D019329:Idazoxan; D010646:Phentolamine