The effect of intrahypothalamic infusions of dopamine and noradrenaline on ovulation in reserpine-treated female rats.

Abstract

SUMMARY Cyclic female rats were treated with reserpine (5 mg/kg) on the 2nd day of dioestrus (15.00 h) or on the day of pro-oestrus (11.30 h) to produce a total or partial depletion of brain amines. Ovulation was inhibited in 18 out of 21 rats. Intrahypothalamic infusions of 0·4–80 μg dopamine or noradrenaline on the afternoon of pro-oestrus did not restore ovulation in reserpine-treated rats. In normal pro-oestrous rats, 80 μg dopamine significantly inhibited ovulation, whereas 80 μg noradrenaline had no significant effect. Electrochemical stimulation of the basal hypothalamus or the administration of luteinizing hormone induced ovulation only in those animals treated with reserpine at pro-oestrus. The results indicate that reserpine exerts a marked peripheral effect when given on the 2nd day of dioestrus and has a partial effect on the ovaries when administered at pro-oestrus. The failure of monoamines to induce ovulation suggests that some aminergic synapses involved in gonadotrophin release may lie outside the medial basal hypothalamus. In addition, high levels of dopamine appear to exert an inhibitory action on the release of pituitary gonadotrophins.