Presynaptic action potential

Psychostimulants. Figure 2 Dopamine molecules have two different possible targets. Both ways are initially increased by DAT inhibition caused by methylphenidate pre- and postsynaptic dopamine receptors. Stimulation of postsynaptic receptors results in inhibition of presynaptic action potential generation. On the other hand, presynaptic receptor stimulation leads to a transmission inhibition of action potentials. Therefore, both mechanisms are responsible for a decrease in vesicular depletion of dopamine into the synaptic cleft (adapted from [2]). 

An aspect of NAR function that is very important in its pharmacological manipulation is receptor desensitization. This phenomenon can be experimentally demonstrated in the set-up depicted in Figure 9.7 Stimulating electrodes produce presynaptic action potentials, which induce release of acetylcholine into the synaptic cleft. Acetylcholine will trigger postsynaptic action potentials, which in turn are de-... 

Figure 9.7. Desensitization of the nicotinic acetylcholine receptor. a Experimental setup. Presynaptic action potentials were triggered, and postsynaptic ones were detected using two separate sets of electrodes, b Perfusion of the synapse with extraneous acetylcholine (during the time interval indicated by the horizontal brace) brings about a sudden depolarization. Continuous presence of acetylcholine rapidly suppresses the response to presynaptic action potentials also, the membrane potential returns to levels near the resting potential. Discontinuation of the acetylcholine results in restoration of response to presynaptic stimuli.

The function of a synapse is to stop transmission and normally there are many presynaptic impulses before one postsynaptic impulse is set up. Thus if there are 20 presynaptic action potentials setting up one postsynaptic action potential, the synaptic ratio would be 20 1. In the cockroach, if the ChE decreased, the efficacy of the... 

DTncamps, B.L., C. Meunier, M.-L. Monnet, L. lami, and D. Zytnicki (1998). Reduction of presynaptic action potentials by pad model and experimental study. J. Comput. Neurosci. 5,141-156. 

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