The function of the preoptic, mammilaris lateralis and ruber nuclei in normal and sexually inactive male chickens.

Male chickens were lesioned and canulated at five weeks of age. Lesions were located in the mammilaris lateralis (ML) and Ruber (Ru) nuclei. Cannulas filled with testosterone propionate (TP) were positioned in the praeopticus paraventricularis magnocellularis (PPM) area of the hypothalamus. The mating behavior of lesioned birds was tested at maturity while mating behavior of cannulated birds was evaluated at eight weeks of age. Males hatched from eggs dipped in 2 g% TP were designated TP birds. The TP birds exhibited a marked decrease in their sexual behavior responses and lesioning did not alter this effect. TP birds with cannulas in the PPM nuclei were stimulated to attempt to mate. These data indicate that TP birds failed to mate because of an interference in the development of the PPM nuclei. Bilateral lesions in the ML nuclei did not significantly influence sexual behavior while lesions in the Ru nuclei increased the sexual response. Therefore, the mammilaris region in the chicken's hypothalamus does not inhibit mating behavior while the Ru nucleus may be an inhibitory center for mating behavior in the chicken.