Biphasic non‐adrenergic, non‐cholinergic relaxations of the mouse anococcygeus muscle

Open Access
Publisher Website
Google Scholar
Abstract
Trains of field stimulation of 60 s duration caused a biphasic relaxation of carbachol (50 μm)‐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 μm), neostigmine (1 μm), (+)‐tubocurarine (100 μm), or apamin (500 nm). Biphasic relaxations were observed in muscles from 6‐hydroxydopamine pretreated mice. Haemolysed blood (10, 40, and 100 μm) 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.