Figure 4.

Interaction of the muscarinic antagonists methoctramine and pirenzepine with carbachol on the evoked overflow of tritium from vas deferens of M₃-knockout mice. After preincubation with ³H-noradrenaline, tissues were superfused and stimulated six times by 20 pulses at 50 Hz (S₁–S₆). Carbachol was added at increasing concentrations (abscissae) before S₂–S₆. Carbachol was given either alone or combined with the indicated antagonists which were present throughout superfusion. Ordinates, evoked overflow of tritium, calculated from S_n/S₁ ratios and expressed as a percentage of the corresponding control (no carbachol). Means±s.e.m. from n=15–19 tissue pieces. Significant differences from carbachol alone: ^#P<0.05.