Melanotropic drugs and retinal functions. II. Effects of phenothiazine and rifampicin on the sheep ERG.

The acute effects of chlorpromazine, promethazine and rifampicin on the a-, b- and c-waves of the conventional electroretinogram (ERG) were studied in sheep. Iv administration of chlorpromazine and promethazine resulted in a b-wave amplitude decrease and an initial c-wave amplitude decrease, followed by cyclic amplitude changes resembling damped oscillations. Iv injections of rifampicin, however, resulted in cyclic changes of the c-wave amplitude without initial concomitant b-wave changes. The results of the present study indicate that rifampicin has a selective influence on the pigment epithelial cells, while chlorpromazine and promethazine seem to have more generalized retinal effects on both the neuroretina and the pigment epithelial cells.