Influence of rabbit cold adaptation on the depressor muscarinic cholinergic reaction of the arterial pressure of the hind limb vessels and the small intestine in situ and the systemic arterial pressure

Abstract

Modification of the main parameters of cholinergic reactions in rabbits, i.e., of the specific sensitivity to agonists (EC50), maximal reaction values (Pm) of arterial pressure in the hind limb vessels and small intestine in situ, and systemic arterial pressure after adaptation to cold for 1, 5, 10, and 30 days has been investigated. The depressor reaction to acetylcholine (muscarinic cholinergic receptors agonist) was established to correspond to the model p = (PmAn)/(EC(50)(n) + An) with n=1. In the control EC50 was equal to 0.85, 1.01, and 1.21 nmol/kg, while Pm equaled 100, 32.6, and 61.2 mm Hg for the hind limb vessels, small intestine in situ, and systemic arterial pressure, respectively. As a result of rabbits adaptation to cold in situ, qualitatively similar modifications in the EC50 and Pm value in the hind limb vessels and in the small intestine occurred with correlation coefficient r = 0.83 for the EC50 parameters and r = 0.74 for the Pm parameters. No correlations between EC50 and Pm in the systemic arterial pressure were observed.