Regional and Species Heterogeneity of Vascular Responses: Cholinergic Muscarinic Regulation of Motor Function of Blood Vessels of Rat and Frog

Cholinergic muscarinic regulation of the motor function in several large blood vessels receiving adrenergic innervation of various degree of density was studied in the rat and the brown frog. The presence of the cholinergic component in the vascular nerve plexus and of muscarinic cholinoreceptors (M-ChR) in the vascular wall was studied by recording isometric contractions of isolated vessels in response to electric stimulation of nerves and to action of an agonist of M-ChR, 5-methylfurmetide, cholinomimetic ACh, and muscarinic cholinoblocker atropine. Cholinergic vasoconstrictory nerves were found in the vascular plexus of the rat portal vein and frog pulmonary artery, whereas M-ChR, in all vessels studied, whether they receive or do not receive the cholinergic vasoconstrictory innervation. The role of cholinergic nerves and the initial functional state of the vessels in the vascular reaction to stimulation of M-ChR as well as the regional heterogeneity of vascular responses and species heterogeneity of muscarinic cholinergic control associated with animal behavior and its habitat were demonstrated. The data obtained confirm the absence of uniformity in the structural and functional organization of blood vessels and, thereby, indicate differentiation of the mechanisms of vasomotor regulation in different zones of vascular bed in different species of vertebrate animals.