REAL-TIME DETECTION OF MITOCHONDRIAL INHIBITION AT FROG MOTOR-NERVE TERMINALS USING INCREASES IN THE SPATIAL VARIANCE IN PROBABILITY OF TRANSMITTER RELEASE

The effects of Hg2+, methyl mercury, and flufenamic acid, all of which inhibit mitochondria, were examined at frog motor nerve terminals. Un biased estimates of m (no, of transmitter quanta released), n (no, of functional release sites), p (probability of release), and var, p (spa tial variance in p) were obtained using K+-induced asynchronous neuros ecretion (m, n and p not having the same definitions as with nerve-evo ked release). Transient but significant increases in m, n, p and var, p were found with all three agents. These findings indicate that mitoc hondrial inhibition and release of sequestered Ca2+ can be detected as a real-time increase in var, p. The results also suggest that changes in var, p might be used to differentiate between cellular (membrane) and subcellular (organellar) actions of drugs at the nerve terminal.