Effects of catecholamines on the horizontal cell membrane potential in the fish retina

The effects of catecholamines (CA) and certain related compounds on the horizontal cell membrane potential were examined in the retina of the teleost (Eugerres plumieri). Each CA compound (dopamine, noradrenaline, and adrenaline) had a similar effect on each class of horizontal cell (photopic L- and C-type, scotopic L-type). The threshold effect, seen with 25-50 microM CA, was an enlargement of both center and surround responses in general. At higher concentrations (100-200 microM), CA augmented the center response and attenuated the surround considerably; these reciprocal changes usually were associated with moderate depolarization. Recovery took place in 15-20 min. The results indicate that up to a certain concentration CA do not affect directly the transmission from photoreceptors to horizontal cells. The lateral propagation of S-potential, however, appears selectively affected by CA. alpha-Methylnoradrenaline, 5-hydroxydopamine, and serotonin caused the same effect on horizontal cells as CA. Reserpine, clonidine, and L-dopa mimic the CA effect only after prior application of CA. Phentolamine blocked while propranolol, haloperidol, and pimozide did not influence the DA effect. We conclude that alpha-adrenergic receptors probably are involved in the CA-induced changes observed in horizontal cells.