Phorbol esters and forskolin infused into midbrain central gray facilitate lordosis

Several peptides, when infused into the MCG, facilitate lordosis in estrogen-primed female rats. Since these peptides can act through cAMP and/or protein kinase C, and these second messenger systems have been implicated in neuromodulation, this study examined if pharmacological agents which stimulate these systems would facilitate lordosis. Ovariectomized female Fisher rats were given bilateral cranial cannulae targeted to the MCG, or cortex dorsal to MCG, and allowed at least a week to recover. Forty-eight hours after injection of 1.25 micrograms estradiol benzoate (EB), 1 microliter of each of the following was infused into the MCG (n=8-12): 1) forskolin (5 micrograms/microliter 50% DMSO); 2) phorbol-20-oxo-20-deoxy-12,13-dibutyrate (PBu; 5 micrograms/microliter 50% DMSO); 3) both forskolin and PBu (2.5 micrograms of each/microliter); 4) vehicle (50% DMSO). In a separate study of identical design, 1 microliter of another phorbol ester (12-myristate 13-acetate) was infused into the MCG of EB-primed rats. Forskolin and phorbol esters each facilitated lordosis maximally at 60-90 minutes after infusion. Combining both agents also facilitated lordosis, and vehicle had no effect. These results suggest that infusing agents which stimulate cAMP and protein kinase C into the MCG can facilitate lordosis in estrogen-primed female rats.