Figure 2. Dose-response relationships of muscarinic antagonists on follicular responses to ACh.

A, effect of 4-DAMP on F_in generated by 800 nm ACh. The traces on the right show 4-DAMP blockade of F_in elicited by ACh; the trace on the left is the control current. Wash periods were of 10 min. Data from a single follicle. B, blocking effect of 1 μm PZP, TPC, MTT or 4-DAMP on 8 nm ACh inhibition of I_K,cAMP generated by 2 μm ADE (open bar below each trace). Superimposed traces in each group correspond to control current (ADE alone; 1), I_K,cAMP inhibition in the presence of ACh and ADE (2), and the same as 2 plus the antagonist which was superfused for 100 s before ACh application (3). Wash intervals were of 15 min. Data from different follicles (2 frogs). C and D, dose-antagonist relationships for the effect of 4-DAMP (squares), MTT (circles), PZP (triangles) and TPC (diamonds) on F_in activation (C) and I_K,cAMP inhibition (D) elicited by ACh at the EC₅₀ concentration. Curves were fitted using the same equation as for Fig. 1D, and each point represents the mean of 4-5 follicles from 2 frogs. I_K,cAMP was generated by 2 μm ADE or 2 μg ml⁻¹ FSH.