Effects of Drugs That Modify Brain Monoamine Concentrations on Photoperiodically-Induced Testicular Growth in Coturnix Quail (Coturnix coturnix japonica)1

Abstract

The monoamine oxidase inhibitor tranylcypromine (TCP) increases brain dopamine (DA), norepinephrine (NE) and serotonin (5-HT) levels and inhibits photoperiodically-induced testicular growth in quail. Blockade of catecholamine synthesis by α-methyl-tyrosine (MT) in TCP treated quail preferentially elevates 5-HT levels and does not interfere with TCP inhibition of the gonads, however, treatment with parachlorophenylalanine (PCPA) reduces 5-HT and DA and antagonizes the action of TCP. Treatment with PCPA alone causes further augmentation of testicular response to photostimulation and reduces 5-HT and DA levels in the brain, whereas 5-hydroxytryptophan (5-HTP) administration elevates central 5-HT stores and partially inhibits testicular development.