Strontium as a Substitute for Calcium in the Process of Transmitter Release at the Neuromuscular Junction
AT the neuromuscular junction1, as well as at neuronal synapses2, calcium plays an essential and direct part in the process whereby depolarization of the presynaptic nerve terminal leads to release of the transmitter substance. It is also known that a nerve impulse releases the transmitter in quantal form, that is, in discrete multi-molecular amounts of a fairly standard size, and that calcium acts by increasing the probability of such transmitter release. The question is raised whether other ions can replace calcium in this process, and if so, is the transmitter still released in quantal form ? Or is the quantal nature dependent on the specific combination of calcium with a receptor in the nerve membrane ?