Pharmacological studies on the noradrenergic control of luteinizing hormone secretion in the domestic fowl.

A neuropharmacological approach was utilized in order to investigate catecholaminergic involvement in the control of LH secretion in the domestic fowl. Inhibition of catecholamine synthesis by alpha-methyl-p-tyrosine (alpha Mpt) at several doses was accompanied by significant reductions in the circulating LH concentration of 6-week-old male cockerels. Plasma LH was similarly depressed following the selective inhibition of NE synthesis by either diethyldithiocarbamate (DDC) or FLA 63. Blockade of alpha 1-adrenergic receptors with phenoxybenzamine was consistently associated with precipitous declines in plasma LH concentrations. Stimulation of alpha-adrenergic receptors by phenylephrine and clonidine elevated circulating LH levels. Activation of the dopaminergic system by apomorphine depressed LH release. However, pimozide was without effect. These data suggest that norepinephrine is involved in the stimulation of LH release, while dopamine may exert an inhibitory influence. Evidence of some stimulatory beta-adrenergic effect is also described.