Calcium-dependent release of neurotransmitters is a crucial step in virtually all aspects of central and peripheral neuron function but this process remains poorly understood due, primarily, to the generally small size of nerve terminals. Previously, we have demonstrated that the calyx- type of presynaptic nerve terminal of the chick ciliary ganglion can be used to record single calcium channel activity at a pre-synaptic nerve terminal release face. We now report the following studies based on this preparation: (a) examination of transmitter release gating at the release site; (b) search for ligand~gated ion channels on the nerve terminals; and (c) investigation of the structure of the nerve terminal release face using atomic force microscopy (AFM). We have found that the release of a transmitter quantum can be gated by a single calcium channel opening and the influx of about 180 calcium ions. We have also obtained the first direct recordings of ATP and acetylcholine (ACh) receptors on the presynaptic nerve terminal. We have used the AFM to provide preliminary evidence for the localization of presynaptic calcium channels. Finally, in order to extend these approaches to the mammalian central nervous system, we are developing an isolated hippocampal mossy fiber terminal preparation suitable for patch-clamp recording.
