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Adrenoceptor mechanisms underlying imipramine-induced memory deficits in rats

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, PO Box 13145-784, Tehran, Iran; zarinmr{at}ams.ac.ir

Maryam Ghiasvand

Houman Homayoun

Parvin Rostami

Bijan Shafaghi

Simin Khavandgar

Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran

The post-training administration of tricyclic antidepressant imipramine impairs memory consolidation in the passive avoidance task. The present study investigated the effects of intrahippocampal (i.h.) injection of adrenoceptor agents on imipramine-induced (2–8 µg/rat) amnesia. The administration of the 1-adrenoceptor agonist phenylephrine (0.05 µg/rat) and the 1-adrenceptor antagonist prazosin (0.5 µg/rat) did not alter the effect of imipramine. The lower doses of phenylephrine (0.005 and 0.015 µg/rat) impaired, while the higher dose of the drug (0.025 and 0.05 µg/rat) improved retention. The effect of phenylephrine was not altered by prazosin (0.5 and 1 µg/rat) pretreatment, although prazosin alone decreased retention latencies. The 2-adrenoceptor antagonist yohimbine (0.5 and 1 µg/rat) decreased the response induced by imipramine. However, the 2-adrenoceptor agonist clonidine (0.08 µg/rat) did not alter the effect of the drug. Clonidine (0.15 and 0.3 µg/rat) by itself decreased, while yohimbine (1 and 2 µg/rat) increased retention latencies. Yohimbine pretreatment attenuated the effect of clonidine. It is concluded that 2-adrenoceptor mechanism(s) may be involved in imipramine-induced impairment of memory.

Key Words: adrenoceptor agents • amnesia • imipramine • passive avoidance task • rat

Journal of Psychopharmacology, Vol. 17, No. 1, 83-88 (2003)
DOI: 10.1177/0269881103017001709


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