Modulation of glutamate receptor expression by gonadal steroid hormones in the rat striatum

The non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist dizocilpine (MK-801) attenuates morphine-induced immediate-early gene expression in the rat striatum in a sexually dimorphic manner that depends in part on gonadal steroids. To determine if this effect was dependent on modulation of glutamate receptor gene expression, we studied the effect of gonadal hormones on levels of the NR1 subunit of NMDA receptor and the GluR2 subunit of the AMPA-subtype of glutamate receptor in the rat striatum, using autoradiographic immunocytochemistry. We found that ovariectomy decreased GluR2 immunoreactivity in the striatum, but no changes were seen in levels of NR1 following gonadectomy in either sex. Thus, the effects of gonadal steroids on NMDA receptor-mediated responses are not due to regulation of NR1 expression.