The functional activity of hypothalamic 5-hydroxytryptamine neurones in broody bantam hens.

An assessment was made of the possible role of hypothalamic 5-hydroxytryptamine (5-HT) in the regulation of prolactin secretion in broody bantam hens. Prolactin secretion was stimulated less in incubating hens deprived of their nests for 24 h (nest-deprived) than in laying hens after administration of the 5-HT receptor agonist quipazine, or precursor 5-hydroxytryptophan. One type of 5-HT-binding site was found in the anterior and posterior hypothalami of out-of-lay, incubating and laying hens. Differences in prolactin secretion in these birds could not be accounted for by changes in the abundance of this type of 5-HT-binding site. Another type of 5-HT-binding site, with a higher density but lower affinity, was found in the anterior hypothalami of laying hens. No specific 5-HT-binding sites were found in the anterior pituitary gland. The turnover rates of 5-HT were compared in the anterior and posterior hypothalami of laying, incubating and nest-deprived hens. The turnover rates were estimated from the rate of accumulation of 5-HT after inhibiting its catabolism using the monoamine oxidase inhibitor, pargyline, or by measuring the ratio of the concentrations of 5-HT and its major metabolite, 5-hydroxyindole acetic acid. Both methods of measurement gave the same results. The turnover of 5-HT was increased in the anterior but not posterior hypothalami of incubating hens when compared with laying or nest-deprived hens. There was also a significant increase in turnover of 5-HT in the posterior hypothalami in nest-deprived hens when compared with laying or incubating birds.(ABSTRACT TRUNCATED AT 250 WORDS)