Effects of the intravitreal administration of dopaminergic ligands on the b-wave amplitude of the rabbit electroretinogram

In the retina of mammals, dopamine (DA) is generally released by amacrine cells and is known to alter the physiology of most retinal cells. It is well known that DA reduces the amplitude of the b-wave of the electroretinogram (ERG) in rabbit. However, the specific receptor subtypes that mediate this action have not yet been elucidated. To do this, we recorded flash ERGs before and after the intravitreal injection of D-2-like DA receptor agonists (SKF38393, A77693) and antagonist (SCH23390), and of D-2-like agonist (R(-)-propylnorapomorphine hydrochloride; NPA) and antagonist ((S)-(-)-sulpiride). Contralateral control eyes were injected with the vehicle only. Both D-1 agonists provoked a reduction of the ERG b-wave amplitude (34.0% and 59.2% of the pre-injection level. respectively). The D-2-like agonist NPA had no significant effects on ERG components. Unexpectedly, both D-1- and D-2-like antagonists also reduced the b-wave amplitude (28.9% and 59.8%). Overall, these data suggest that the previously described effect of DA on the rabbit ERG b-wave came from activation of D-1-like receptors. On the basis of the effects observed with D-2-like antagonist, a subtle contribution of D-1-like presynaptic receptors cannot be ruled out. (C) 2004 Elsevier Ltd. All rights reserved.