Neural structures associated with reproductive development and photoperiodic effects in male chicks (Gallus...

White Leghorn chicks given parasagittal knife cuts that isolated the hypothalamus from lateral connections displayed early maturation of the testes. When the operated chicks were subsequently exposed to a long-day photoperiod known to stimulate gonadal development, no additional increase in the size of the testes occurred. In contrast, controls demonstrated a marked development of the gonads that surpassed testes size of experimentals. An additional study was designed to determine whether the archistriatum, a telencephalic structure that has significant projections to the hypothalamus, may be involved in the earlier onset of puberty shown by knife-cut chicks. Three different sets of brain cuts were made that severed projections from the archistriatum to the hypothalamus. None of the knife cuts affected development of the gonads when the birds were examined six weeks after surgery. Two of the three sets of knife cuts, however, effected a significant reduction in food intake, and operated chicks also displayed a significantly lower body weight compared to controls (p less than 0.05).