Figure 5. Contractile activity in a strip of smooth muscle dissected from a pig urethra.
The tissue develops spontaneous tone after an initial tensioning to 1 g. It responds to stimulation of its intrinsic nerves (EFS) with a biphasic relaxation which is blocked by TTX. Applications of noradrenaline (NAd) and acetylcholine (ACh) contract the tissue further, but the nitric oxide donor sodium nitroprusside (SNP) and the KATP channel opener cromakalim both relax the tissue, as does removal of extracellular calcium. Adapted from Greenland et al. (1996).