The influence of testosterone implantation in the brain and pituitary on pituitary gonadotropin levels in Atlantic Salmon parr

Implantation of testosterone pellets in the brain or pituitary of male and female parr caused an increase in pituitary gonadotropin, and in males tended to stimulate spermatogenesis. The most effective implant locations were the nucleus lateral tuberis in the ventrobasal hypothalamus and the pituitary. This influence of testosterone on the brain and pituitary may be involved in control of precocious sexual maturation. also have an influence on the onset of precocious sexual development in male parr under normal conditions cannot be discerned by the present study, but our results suggest that it may be a part of the mechanism. The lack of evidence for ovarian deve- lopment in the females suggests that gonadotropin secretion was insufficient or other physiological conditions were not appropriate for the ovaries to respond.