Electrophysiological analysis of the cholinergic effects of cimetidine and ranitidine.

The study takes the form of an analysis of the effects of cimetidine and ranitidine (2 x 10(-4) M) on 9 electrophysiological parameters, using a single frog sciatic nerve-sartorius muscle preparation. The parameters evaluated were: (i) mean end-plate potential (e.p.p.) amplitude, and mean 50%-corrected e.p.p. amplitude, (ii) mean rise time (RT), (iii) mean half-decay (HD), (iv) mean miniature end-plate potential (m.e.p.p.) amplitude, (v) mean resting membrane potential (RMP), (vi) mean m.e.p.p. frequency (f), (vii) mean quantal content (m), (viii) quantum release probability (p), and (ix) number of active sites (n) in the nerve terminal. Marquardt analysiswas used in order to determine the effects of cimetidine and raniditine on end-plate potential kinetics. At the concentration assayed only ranitidine showed a marked blocking effect at postsynaptic level as well as a less pronounced presynaptic effect. The time course of the e.p.p.'s is also more affected by raniditine, though the kinetic behaviour observed is not a unique feature of this drug alone.