In cats bilateral sympathectomy or administration of reserpine results in a marked reduction in concentration of myocardial catecholamines. The contractility of papillary muscles from such animals is significantly less than that of muscles from untreated animals. These findings demonstrate the importance of normal levels of myocardial catecholamines in the maintenance of normal cardiac contractility.

Isolated, atropinized, rat atria exhibited positive inotropic responses to bretylium, guanothidine and tyramine. These responses were prevented by treatment of the animal with reserpine, or by addition of dichloroisoprenaline to the organ bath. The positive inotropic effects of these compounds on atria from reserpinized animals were restored by incubation of the tissue with noradrenaline. On the basis of these findings it is concluded that the cardiac stimulation by bretylium, guanethidine and tyramine involves the release of catechol amines. The usually reported increase in sensitivity of the myocardium from reserpinized animals to noradrenaline was not observed. The influence of bretylium and guanethidine on cardiac uptake and release of noradrenaline was also studied with the rat. Guanethidine decreased the concentration of catechol amines and inhibited the uptake of exogenous noradrenaline, while bretylium had no effect on either. The decrease in concentration of cardiac catechol amines produced by guanethidine was prevented by treatment of the animal with bretylium or with l-phenyl-2-hydrazinopropane (pheniprazine), a monoamine oxidase inhibitor.

Chicks hatched from eggs injected with reserpine prior to incubation showed impaired performance in detour learning between 7 and 17 days of age, although locomotor activity and brainstem catecholamine levels were not significantly different from controls at 18 days. Day‐old chicks injected with the same amount of drug showed no significant depletion of brainstem catecholamines 7 days later, supporting the possibility that behavioral effects were due to exposure to the drug during embryogenesis.

No abstract

SPARBER, S. B., and SHIDEMAN, F. E. (1968). Prenatal Administration of Reserpine and Its Etfect upon Hatching,Behavior, and Brainstem Catecholamines of the Young Chick. DEVELOPMENTAL PSYCHOBIOLOGY, l(4) 236244. 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, reserpinc 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.