Hypothalamic biogenic amine levels in broiler chicks showing advanced sexual maturation.

Parasagittal knife cuts through the lateral hypothalamic area of 2-wk-old male broiler chicks induced precocious testes development. Two experiments were performed to determine whether hypothalamic biogenic amine levels in these chicks were changed by lateral hypothalamic deafferentation. In Experiment 1, chicks responding to surgery with advanced sexual maturation had reduced levels of norepinephrine (NE), epinephrine (E), and homovanillic acid (HVA) in the anterior hypothalamus and elevated levels of dopamine (DA) and serotonin in the median eminence, compared with controls. In Experiment 2, NE and HVA were reduced in the anterior hypothalamus of nonresponders. Dopamine was reduced in the anterior hypothalamus of nonresponders and elevated in the median eminence of responders. Serotonin was found to be higher in the median eminence of nonresponders. The increased DA in the median eminence suggests an excitatory role for this neurotransmitter in gonadotropin release at puberty.