Effect of stress on the catecholamine content of the adrenal gland of intact and bursectomized chicks

The autonomic nervous system and chromaffin tissue: neuroendocrine regulation of catecholamine secretion in non-mammalian vertebrates

If severe enough, periods of acute stress in animals may be associated with the release of catecholamine hormones (noradrenaline and adrenaline) into the circulation; a response termed the acute humoral adrenergic stress response. The release of catecholamines from the sites of storage, the chromaffin cells, is under neuroendocrine control, the complexity of which appears to increase through phylogeny. In the agnathans, the earliest branching vertebrates, the chromaffin cells which are localized predominantly within the heart, lack neuronal innervation and thus catecholamine secretion in these animals is initiated solely by humoral mechanisms. In the more advanced teleost fish, the chromaffin cells are largely confined to the walls of the posterior cardinal vein at the level of the head kidney where they are intermingled with the steroidogenic interrenal cells. Catecholamine secretion from teleost chromaffin cells is regulated by a host of cholinergic and non-cholinergic pathways that ensure sufficient redundancy and flexibility in the secretion process to permit synchronized responses to a myriad of stressors. The complexity of catecholamine secretion control mechanisms continues through the amphibians, reptiles and birds although neural (cholinergic) regulation may become increasingly important in birds. Discrete adrenal glands are present in the non-mammalian tetrapods but unlike in mammals, there is no clear division of a steroidogenic cortex and a chromaffin cell enriched medulla. However, in all groups, there is an obvious intermingling of chromaffin and steroiodogenic cells. The association of the two cell types may be particularly important in the amphibians and birds because like in mammals, the enzyme catalysing the methylation of noradrenaline to adrenaline, PNMT, is under the control of the steroid cortisol.

Effect of stress on serotonin, norepinephrine, epinephrine and corticosterone contents in the soft-shelled turtle

1. Adult soft-shelled turtles were exposed to hyperosmotic and dehydration stresses. 2. Acute treatment for 0.5, 1 or 2 h with sodium chloride (3.6%, single intramuscular injection, 2 mL volume) caused depletion of pineal serotonin contents followed by elevation of norepinephrine and epinephrine levels. In addition, it depleted corticosterone and norepinephrine from the adrenal gland. 3. The serotonin level also decreased with a concomitant increase of 5-hydroxyindoleacetic acid but without any discernible change in catecholamine content after chronic treatment with sodium chloride (3.6%, 0.5 mL daily for 7 days). 4. Dehydration for 7 days brought about depletion of serotonin and epinephrine levels and elevation of norepinephrine level. 5. The findings suggest that hyperosmotic stress has a definite influence on pineal-paraphyseal serotonin, 5-hydroxyindoleacetic acid, norepinephrine and epinephrine concentrations, and adrenal corticosterone and norepinephrine contents in Lissemys turtles. Dehydration stress also modulates pineal-paraphyseal serotonin, norepinephrine and epinephrine concentrations.