Prenatal administration of reserpine: Effect upon hatching, behavior, and brainstem catecholamines of the young chick

An avian species (the domestic chicken) was used in an attempt to determine the effects of reserpine upon the developing embryo and newly hatched chicken. When reserpine was injected into the yolk sac of the fertilized egg prior to incubation, there was a decrease in hatchability which was log‐linearly related to the dose of reserpine; the older the embryo at the time reserpine was injected, the less the effect on hatchability. In addition to increasing mortality, reserpine caused a delay in hatching which was also dose dependent. During the first 7 days of incubation, injection of reserpine into the egg in a dose (0.1 mg/kg of egg) that did not appreciably affect hatching significantly decreased following in an imprinting situation. The same dose of reserpine given to older (15‐day‐old) embryos caused a significant increase in following. Week‐old chicks hatched from eggs injected with the drug prior to incubation exhibited a significant decrease in catecholamines (norepinephrine and epinephrine) in the brainstem, and significantly fewer avoidance responses in a conditioned escape/avoidance situation.