Effect of histamine, phencyclidine, phenoxybenzamine and gamma-aminobutyric acid on ovulation and quality of ova in rats.

The gonadotropin-stimulated prepuberal female rat is a good model for the study of drugs affecting ovulation and the quality of ova released. Various pharmacological agents, such as histamine, phencyclidine, phenoxybenzamine (PBZ) and gamma-aminobutyric acid (GABA), were tested in this paradigm for evaluation on incidence of ovulation, number of ova released and degeneration in the ova shed. A dose of 25 iu of pregnant mare serum gonadotropin (PMS) was found to be most effective in inducing superovulation in these rats. The percentage of degenerative eggs obtained was least in this dose group. Histamine and GABA appeared to cause an increased number of oocytes to be released, while phencyclidine reduced the number of animals responding to PMS treatment. PBZ was effective in completely blocking ovulation only when given before the LH surge occurred in the treated animals. The quality of ova released was affected by GABA, phencyclidine and PBZ. GABA and phencyclidine reduced the incidence of degenerative oocytes while treatment of animals with PBZ at the time of PMS administration increased the degenerative oocytes. It is suggested that more studies be carried out to observe the effect of various drugs, administered shortly before ovulation, on ovum quality.