THE EFFECTS OF PRENATAL EXPOSURE TO COCAINE ON THE DOPAMINERGIC CELLSIN THE RAT RETINA - AN IMMUNOCYTOCHEMICAL AND NEUROCHEMICAL STUDY

There is a growing consensus that the development of the eye is affect ed by prenatal exposure to cocaine. Considering that the retina is aff ected by prenatal cocaine exposure, that this drug affects the dopamin ergic systems, that the dopaminergic cells in the retina show a well-d efined pattern of development and that they can be specifically staine d in wholemounts by the antibody anti-tyrosine hydroxylase (TH), this study was undertaken to evaluate the effects of in utero cocaine expos ure on the dopaminergic cells of the rat retina. Pregnant Wistar rats were given 60 mg (kg body weight)(-1) day(-1) of cocaine hydrochloride , subcutaneously, from gestational days 8 to 22. Control groups of pre gnant rats were pair-fed. At PND14, 30 and 90, male offspring from dif ferent litters were perfused with fixative and the retinas processed a s wholemounts and immunostained with the antibody anti-TH, Rats from o ther groups were decapitated at the same post-natal ages. the retinas dissected and processed by neurochemical techniques to measure the con centrations of dopamine, its metabolites and the turnover of dopamine. There was a significant increase of the retina surface area between P ND14-30 in the control group, which was not found in the cocaine group . The density of the immunostained small TH cells was lower in the coc aine groups, No drug-effects were detected in the density of the large TH cells. The densities of the total large and small cells in the sup erior, inferior and nasal hemiretinas were similar to those found in t he whole retinas: however, in the temporal hemiretinas of the cocaine groups, the density of the large TH cells was higher and of the small TH cells was lower than in controls, resulting in an absence of effect s on the total density of TH-cells in this hemiretina. A transient inc rease in the level of dopamine metabolite (DOPAC) and of the turnover of dopamine at PND14 was detected in the cocaine groups. All quantitat ive parameters reached normal values, in all groups, at PND90. These r esults show that, during the critical periods in which catecholamines can influence the development of neurons, cocaine transiently affects the pattern of dopaminergic neurons in the retina. This may have funct ional importance due to the role of this neurotransmitter as a regulat ory and/or trophic factor in developing neuronal circuitries. (C) 1996 Academic Press Limited