Sex Hormones and Their Effect Upon Conditioned Responses in the Rudd (Leuciscus Leuciscus)

Since the effects of the sex hormones on the fish do not show any sex differences, the results of the experiments on both males and females can be summarized together. (1) Oestrone inhibited an artificially produced conditioned response. (2) Prolan and progesterone had no effect upon the functioning of the conditioned response, although several or prolonged injections of prolan are likely to cause inhibition due to natural causes, e.g. maturation of ova in oviducts. (3) Progesterone, although foreign to the Pisces, terminates the inhibition brought about by previous injections of oestrone. (4) Death caused by injection of progesterone can be prevented by injection of oestrone.