Higher Ester Levels Research Articles

Ester and stimulus frequency mediated perturbations of response patterns from cat soleus tissues

Contractile response patterns evoked by the tertiary aminoester tropine p-tolylacetate (II) and its quaternary methiodide (I), on steady-state infusion into the in situ cat soleus neuromuscular preparation, have been studied as a function of ester concentration and frequency of electrical stimuli to nerve. With spaced bursts of stimuli to nerve producing isometric response bursts from muscle, intraarterial administration of either ester results in a biphasic action pattern; at low ester concentrations small degrees (5–10%) of response amplification are met, with a progressive transition to response blockade at higher ester levels. For the quaternary ester I, the effects of individual variation in concentration of agent and mean frequency of stimulus mode employed appear to be inversely related in production of response amplification from soleus muscle, with pairing of high concentration-low frequency or conversely low concentration-high frequency parameters leading, respectively, to optimum amplification. These results are discussed in terms of possible mechanisms governing chemical effects mediated at the soleus neuromuscular junction.