Stimulation of the hippocampus and ovulation in the rat: specific or nonspecific effects

Bilateral electrochemical stimulation (ECS) of the ventral hippocampus (VHPC) or dorsal hippocampus (DHPC) under acute condition at 10.00, 12.00 or 13.00 h on proestrus did no interfere with ovulation. When the same ECS of the VHPC was repeated at 12.00 h proestrus followed by the taking of blood samples at 14.00, 16.00 and 18.00 h under ether anesthesia from the jugular vein, the LH surge and ovulation were significantly (p less than 0.05) inhibited. Acute unilateral ECS of the VHPC or passing the same current through a platinum electrode had no effect on the LH surge. When large electrolytic lesions were bilaterally made in the VHPC with a platinum electrode at 12.00 h of proestrus followed by blood samples, the LH surge and ovulation were also inhibited (p less than 0.05). Large lesions in the caudate putamen also resulted in a significant (p less than 0.05) suppression of the LH surge and the number of ova. These data suggest that (1) electrochemical stimulation of the hippocampus is not inhibitory to ovulation, and (2) acute procedures on the day of proestrus can inhibit LH secretion.