title: Biphasic non-adrenergic, non-cholinergic relaxations of the mouse anococcygeus muscle.
abstract: Trains of field stimulation of 60 s duration caused a biphasic relaxation of carbachol (50 microM)-induced tone in the mouse anococcygeus. The optimal pulse frequency and width were 10 Hz and 1 ms respectively. Tetrodotoxin (31, 124, and 310 nM) caused a dose-dependent reduction in the magnitude of both phases. Neither phase was affected by (+/-)-propranolol (1 microM), neostigmine (1 microM), (+)-tubocurarine (100 microM), or apamin (500 nM). Biphasic relaxations were observed in muscles from 6-hydroxydopamine pretreated mice. Haemolysed blood (10, 40, and 100 microliter/ml) reduced the magnitude of the first phase of nerve-induced relaxation to a greater extent than the second. This effect was reversible. Following a prolonged train of inhibitory nerve stimulation (10 Hz; 10 min) the magnitude of the first phase was reduced only slightly, but the second markedly. The possible relationships between the biphasic relaxation to field stimulation and putative non-adrenergic, non-cholinergic transmitters in the mouse anococcygeus are discussed.
mesh_terms: D000818:Animals; D001769:Blood; D004558:Electric Stimulation; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009119:Muscle Contraction; D009126:Muscle Relaxation; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D014660:Vasoactive Intestinal Peptide