The hypothalamo-neurohypophyseal system in birds.

The hypothalamus is the central integrative structure for the neuroendocrine regulation of body fluid homeostasis. Despite many different modulatory endocrine and peptidergic inputs there are three main neuroendocrine 'channels' involved in osmoregulation: 1. corticotropin releasing hormone (CRH)-adrenocorticotropic hormone (ACTH)-adrenal steroids (aldosterone, corticosterone); 2.

Modulation of arginine vasotocin secretion in chicks by dehydration during embryogenesis.

The influence of low humidity during incubation (LHI) on arginine vasotocin (AVT) secretion in male and female White Leghorn chicken embryos and chicks was investigated. LHI embryos were incubated from day 8 (E8) to E18 at a relative humidity of 32-35%, while control embryos were incubated at 58-62%. In the control groups, plasma AVT gradually increased from E15 to E18, increased sharply during hatching and returned to the E18 level within 4 h.

[Effect of the genotype on the reactivity of the hypothalamo-hypophyseal-adrenal system of chick embryos].

Studies have been made on embryos of two hen lines selected by their reaction to cold stress (highly and lowly reactive ones). The adrenals of 16-day chick embryo react to the injection of the ACTH by synthesis of glucocorticoids and by their secretion into the blood. The rate of this reaction is higher in highly reactive line of hens.

[Formation of a reaction of the hypothalamo-hypophyseal-adrenal cortex system to cooling in chick embryogenesis].

The content of glucocorticoids in the suprarenals and blood of chick embryos increased from the 12th till the 15th day of incubation. The intensive accumulation of glucocorticoids in the glands was accompanied by a relatively small increase of their concentration in blood plasma from the 15th till the 19th day. No adrenocortical reaction to cooling was registered in the 12 and 13 days old embryos.

[Effect of arginine vasotocin, oxytocin and their fragments on the corticosterone content in the blood plasma of chickens of different ages].

Administration of arginin-vasotocin, oxytocin and their fragments had no effect on corticosterone content in the blood plasma of 10-month chickens whereas in 20 and 30-day chickens arginin-vasotocin and its terminal fragment: amid of prolyl-arginil-glycil, considerably increased the corticosterone content. The cyclic fragment of these hormones: tocinic acid, proved ineffective. The adrenocorticotropic effect of arginin-vasotocin obvious in young chickens seems to be due to the terminal part of the molecule.