A voltage-sensitive calcium channel agonist, BayK 8644, and its active isomer, R5417, increases calcium currents in spinal cord (SC) and dorsal root ganglion (DRG) neurons in cell culture under voltage clamp, particularly those currents which are activated between -40 and zero mV membrane potential. These agents do not increase excitatory transmitter output in this system, suggesting that the types of calcium channels sampled in the neuronal cell body may be distinct from those involved in transmitter release from neuronal terminals. Physiological studies of synapse formation between neurons in different compartments of a 3-compartment culture system have begun in conjunction with morphological observations described in Project Z01 HD 00708-03. Chronic stimulation of DRG axons making synaptic connections to SC neurons appear to increase the relative efficacy of these stimulated synapses.
