Role of alpha-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.