Dibutyryl cyclic adenosine monophosphate stimulates in vitro luteinizing hormone-releasing hormone release only from median eminence derived from ovariectomized, estradiol-primed rats

The present study examined the effect of intermittent infusion of dibutyryl cyclic AMP (dbcAMP; 10(-7) M; 10 min on, 20 min off) on in vitro luteinizing hormone-releasing hormone (LH-RH) release from the rat median eminence (ME) derived from immature rats: intact females, intact males, ovariectomized (OVX) females, castrated (CAST) males, ovariectomized, estradiol primed (OVX + E2) females and castrated, estradiol primed (CAST + E2) males. In intact, OVX and CAST conditions, spontaneous LH-RH release from MEs was not modified by dbcAMP infusion. However, E2 implants in OVX and CAST rats selectively affected the responsiveness of MEs to dbcAMP: ME from OVX + E2 were highly responsive to dbcAMP; contrarily, MEs from CAST + E2 were unresponsive to this nucleotide. Therefore, these differences in MEs responsiveness to dbcAMP-induced LH-RH release appear to be dependent upon a critical effect of E2 priming on this tissue in female but not in male rats.