Role of α-Adrenergic Mechanism in Regulating Tonic Luteinizing Hormone Release in Conscious Ovariectomized Rats*

The role of brain catecholamines in controlling tonic LH secretion was studied in unanesthesized, freely moving, ovariectomized rats. Pretreatment with reserpine (10 mg/kg), given 24 h before the experiment, significantly suppressed pulsatile LH secretion in these rats. Intraperitoneal administration of clonidine (1 mg/kg), an alpha-adrenergic stimulating agent, significantly raised plasma LH levels in reserpine-treated rats. On the other hand, the administration of apomorphine (1.5 mg/kg), a dopamine receptor-stimulating agent, had no effect on the plasma LH levels. These findings suggest an excitatory role of noradrenaline, operating through alpha-adrenergic receptors, in pulsatile LH secretion in ovariectomized rats.