PRESYNAPTIC CALCIUM CHANNELS - PHARMACOLOGY AND REGULATION

Voltage-dependent Ca2+ channels are considered as molecular trigger el ements for signal transmission at chemical synapses. Due to their cent ral role in this fundamental process, function and pharmacology of pre synaptic Ca2+ channels have recently been the subject of extensive exp loration employing various experimental techniques. Several lines of e vidence indicate that, at nerve terminals in higher vertebrates, the e voked influx of Ca2+ -ions is mainly mediated by Ca2+ channels of the P-type. The stringent regulation of presynaptic Ca2+ channels is suppo sed to be involved in fine-tuning the efficiency of synaptic transmiss ion. Intrinsic control mechanisms, such as voltage- or Ca2+-dependent inactivation, or modulation of channel activity, either by G-proteins directly or via phosphorylation by protein kinases, may be of particul ar functional importance.