PINEAL ACTIVITY IS UNDER THE CONTROL OF RETINAL D-1-DOPAMINERGIC PATHWAYS

THE role Of dopaminergic pathways in the retina in controlling the fun ctional state of the pineal was investigated. Dopaminergic agents were injected into the eyes of dark-adapted chickens which were maintained in the dark. Changes in the activity of N-acetyltransferase (NAT) in the retina and pineal were then monitored. Injection of the non-specif ic dopamine agonist 6,7-ADTN depressed retinal and pineal NAT. The D-1 -specific agonist SKF38393 did not affect retinal NAT but depressed pi neal NAT. In contrast, quinpirole, a D-2-specific agonist, depressed r etinal NAT, but did not depress pineal NAT. Thus, D-1- rather than D-2 -dopaminergic pathways in the retina are involved in the retinal circu its which control pineal function.