Physiological adaptations to acute stress in the ewe

An investigation of the two major stress pathways, the sympathomedullary system, and the hypothaiamic-pituitary-adrenal (HPA) axis and their role in the mediation of the physiological response to acute stress was undertaken in the sheep. Particular emphasis was given to the metabolic regulation initiated by these two stress pathways. In addition, the specific role of each pathway was assessed. This was achieved by using two different approaches. Firstly, by the active immunisation against ACTH 1-24, which acts to immunoneutralise the glucocorticoid response. Secondly, a pharmacological approach using non-selective adrenergic receptor antagonists. Propranolol HCI, a yff-adrenergic antagonist and phentolamine methane-sulfonate, a or-adrenergic antagonist were used. To determine the contribution of the sympathetic nervous system tyramine HCI, a potent sympathomimeteic agonist compound was infused into sheep.