2 A high-affinity uptake system for dopamine exists in rat retina in vitro; K_m value was calculated as 1.89 μM, V_max value as 1.4 nmol g^-1 tissue h^-1.

3 Dopamine (0.8 and 4 mM) inhibited the spontaneous release of ³H]-glycine from retina, and in the case of 0.8 mM dopamine this inhibitory effect was antagonized by 10 μM (+)-butaclamol but not by 10 μM (-)-butaclamol.

4 The potassium-evoked (25 mM) release of ³H]-glycine from rat retina was similarly inhibited by dopamine (0.4-4 mM) in a dose-related manner when added to the superfusate with the potassium. The effect of 0.8 mM dopamine was antagonized by 10 μM (+)-butaclamol but not by 10 μM (-)-butaclamol.

5 Dopamine (4 mM) significantly reduced the spontaneous release of ³H]-taurine from rat retina.

6 The potassium-stimulated (25 mM) release of ³H]-taurine occurred after the cessation of the depolarizing stimulus. This delayed release of ³H]-taurine was unaffected if dopamine was applied to the superfusate at the same time as the potassium, but it was significantly reduced if dopamine (0.8 and 4 mM) was applied after the depolarizing stimulus had been removed and during the actual amino acid release phase.

7 The inhibition of K⁺-stimulated (25 mM) delayed release of ³H]-taurine by applying dopamine (0.8 mM) after the depolarizing stimulus was blocked by 10 μM (+)-butaclamol but not by 10 μM (-)-butaclamol.

8 The results are discussed with respect to the possible neurotransmitter role for dopamine within the rat retina, and its possible interaction with glycine and taurine.