DIFFERENT TYPES OF CALCIUM CHANNELS MEDIATE CENTRAL SYNAPTIC TRANSMISSION

SYNAPTIC transmission is mediated by calcium entry through voltage-dependent calcium channels in presynaptic nerve terminals1,2. Various types of calcium channel have been characterized in neuronal somata3-6, but it is not clear which subtypes induce transmitter release at central synapses. The N-type Ca2+ channel blocker omega-conotoxin GVIA (omega-CgTx) suppresses the excitatory postsynaptic responses only partially7,8, whereas potassium-induced release of glutamate from brain synaptosomes can be blocked by omega-Aga-VIA (ref. 9), a blocker of P-type calcium channels5,10 and possibly of other types of calcium channels11,12. Here we test type-specific calcium-channel blockers on postsynaptic currents recorded from neurons in thin slices of rat central nervous system13. Inhibitory postsynaptic currents in cerebellar and spinal neurons and excitatory postsynaptic currents in hippocampal neurons are markedly suppressed by omega-Aga-IVA and reduced to a lesser extent by omega-CgTx. The L-type calcium channel blocker nicardipine had no effect. Our results indicate that at least two types of calcium channel mediate synaptic transmission in the mammalian central nervous system.