It has become clear that several species of voltage sensitive calcium channels (VSCC) exist in different tissues and even within the same cell. The different types of these channels can be distinguished on the basis of their voltage and pharmacological sensitivities. We have addressed the question of which types of calcium channels may be involved in neurotransmitter release at central synapses. Nitrendipine, a blocker of VSCC in muscle does not affect neuronal VSCC and similarly has no detectable effect on transmitter release. BayK 8644 is a VSCC agonist increasing one type of VSCC, the L channel, in dorsal root ganglion (DRG) neurons. This agent does not increase transmitter output from either DRG or spinal cord (SC) synaptic terminals. This suggests that the L channel is not involved in transmitter release. DRG and SC neurons and muscle cells have been grown in a three-compartment chamber tissue culture system. Selective growth of axons into chambers containing target tissue as well as synapse formation by axons growing from one chamber to another have been demonstrated.
