From top, presynaptic membrane
potential ([V.sub.pre]), presynaptic Ca currents ([I.sub.Ca]), EPSC, and cumulative release, schematic drawing of vesicle release, are shown.
Activation of the oxytocin receptor on the presynaptic membrane
, resulting in an increase in intracellular calcium concentration, may increase the secretion of the neurotransmitter into the synaptic cleft.
(18,19) Synaptic transmission is triggered by the influx of [Ca.sup.2+] to the presynaptic membrane
and then neurotransmitters such as glutamate, acetylcholine, and GABA are released in the form of vesicles.
When an action potential arrives at the presynaptic membrane
, it produces an influx of calcium ions through voltage-dependent calcium channels.
This process involves the fusion of the presynaptic vesicle, which contains acetylcholine with the presynaptic membrane
and is mediated by a set of SNARE (soluble N-ethylmaleimide-sensitive fusion attachment protein receptor) proteins (Smith & Chancellor, 2004).
NO now travels backward across a chemical synapse to bind to the axon terminal (NO receptor sGC) of a presynaptic neuron, as in normal condition, now acts as impulse generator (at presynaptic membrane
) thus bypasses the normal ANT.
PSD95 is the postsynaptic membrane marker and SYP is the presynaptic membrane
Another explanation is the modulation of neuromuscular transmission, due to lowered number of vesicles fused with the presynaptic membrane
and quantal size of acetylcholin (ACh) per vesicle (Reid et al., 1999).
Choline is recycled by an active pump at the presynaptic membrane
for the formation of more acetylcholine.
cruzi, as well as ischemia and alterations in the presynaptic membrane
densities in the active zones, shows that the abnormal mice NMJ is associated with an activity dependent modulation of the neurotransmission, producing abnormal motor activity and paralysis of the rear limbs mice while still in the acute Chagas'disease.
A neuromuscular junction is comprised of three components--the presynaptic membrane
, the synaptic cleft, and the postsynaptic membrane.
These are contained in vesicles whose membrane can fuse, as a result of the actions produced by the nerve stimulus, with that of the junction (presynaptic membrane
) causing the emptying of the vesicle and the emission of the neurotransmitter.