Effects of antidepressant treatment on inhibitory avoidance behavior and amygdaloid beta-adrenoceptors in rats.
Chronic treatment of rats with a variety of antidepressants results in the down-regulation of beta-1-adrenoceptors in the amygdaloid nuclei. The present study sought to determine if this specific neurochemical effect caused an alteration in inhibitory avoidance conditioning, a behavior considered to be mediated by beta-adrenoceptors in the amygdala. Rats treated chronically with either desipramine (DMI) or phenelzine (PHEN), which down-regulate beta-1-adrenoceptors in the amygdala, or fluoxetine (FLUOX), which does not do this, did not exhibit a deficit in the retention of the inhibitory avoidance task. However, when scopolamine was given prior to acquisition of the task in a dose that, by itself, did not affect retention, DMI- and PHEN-treated rats showed a marked deficit in retention. This effect was also observed after acute administration of these drugs, although they did not down-regulate amygdaloid beta-1-adrenoceptors at this time. It seems that the ability of these antidepressants to potentiate the amnesic effect of scopolamine is unrelated to their effect on beta-1-adrenoceptor number in the amygdala and that the extent of the antidepressant-induced amygdaloid beta-1-adrenoceptor down-regulation is not sufficient, by itself, to cause a deficit in an inhibitory avoidance task.
Department of Pharmacology, University of Texas Health Science Center, San Antonio, Texas, USA.
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D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000679:Amygdala / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects*; D003891:Desipramine / Q000494:pharmacology; D005473:Fluoxetine / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010624:Phenelzine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects* / Q000378:metabolism; D012601:Scopolamine / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D000928:Antidepressive Agents; D018727:Muscarinic Antagonists; D018342:Receptors, Adrenergic, beta-1; D005473:Fluoxetine; D011433:Propranolol; D012601:Scopolamine; D010624:Phenelzine; D003891:Desipramine