DOPAMINE EFFLUX IN THE RAT NUCLEUS-ACCUMBENS EVOKED BY DOPAMINE-RECEPTOR STIMULATION IN THE ENTORHINAL CORTEX IS MODULATED BY ESTRADIOL ANDPROGESTERONE

This study compared the effects of dopamine receptor stimulation in th e entorhinal cortex on dopamine release in the nucleus accumbens, meas ured by in vivo microdialysis in conscious Sprague-Dawley rats, with a nd without oestradiol and progesterone priming. Nonselective dopamine receptor stimulation with apomorphine reduced dopamine release in the nucleus accumbens, an effect which was prevented by injection of cis-f lupenthixol into the entorhinal cortex. Selective D-1 receptor stimula tion with SKF38393 increased dopamine release, whereas selective D-2 r eceptor stimulation with quinpirole did not affect dopamine release. C ombined administration of oestradiol and progesterone potentiated the response to apomorphine and prevented the response to SKF38393. The ef fects of single hormone administration on the response to apomorphine suggested that the modulation was primarily due to oestradiol enhancin g effects of progesterone. Experiments with high [K+] suggested these hormonal effects were exerted predominantly in the entorhinal cortex. The present experiments have demonstrated that dopaminergic modulation of transmission in a cortico-striatal loop linking temporal and prefr ontal cortex is regulated by oestradiol and progesterone. Dysfunction in this system in humans may give rise to affective and cognitive symp toms which may, if initiated by a postpartum fall in oestrogen and pro gesterone concentrations, constitute the core pathophysiology of puerp eral psychosis. (C) 1997 Wiley-Liss, Inc.