A single subcutaneous (sc) injection of picrotoxin in a dose ranging from 3 to 40 mg/kg to proestrous female rats produced sustained clonic-tonic convulsions and resulted in a significant elevation of serum LH levels. FSH release was not stimulated. Serum calcium levels increased, with a positive correlation with the increment of serum LH increase in these animals. Similarly, 5 mg/kg of picrotoxin was effective in inducing an increase in serum LH and calcium, but not FSH, in adult male rats. Pentylenetetrazol in a dose of 120 mg/kg induced sustained clonic-tonic convulsions and stimulated the release of LH, but not of FSH, in both adult male and female rats. An increase in serum calcium levels also was evident. These results suggest that sustained convulsions induce overall excitation of the central nervous system and result in the enhancement of LH release from the pituitary. The mechanism responsible for the differential stimulation of LH and FSH release remains to be clarified.