[Recent advances of strategy for the brain functions--a targeting for tiny presynaptic boutons]

Recent advances in our knowledge of synaptic transmission have been achieved using brain slice preparations. Since the complexes of neuronal networks often make multiple synaptic contacts to a single postsynaptic neuron, the electrical stimulation of presynaptic nerve bundle simultaneously activates not only plural presynaptic axons but also the collateral pathways. Accordingly, the mechanisms of transmitter release from a single presynaptic nerve terminal are poorly understood. Recently, a more simplified preparation of cultured neurons has been developed and the properties of transmitter release were clearly studied. However, little information exists as to whether the release properties and presynaptic modulation of single native terminals behave similarly to terminals formed in culture preparations. We have then develop a mechanical dissociation technique of single CNS neurons attaching functional native excitatory and inhibitory synaptic terminals (boutons). These dissociated neurons exhibit spontaneous synaptic activities, and their presynaptic modulation has been extensively studied. We further visualized single presynaptic boutons onto a synaptic bouton preparation and electrical stimulation was selectively given to one of the boutons. Here we show how such an electrophysiological approach allows us to understand the transmitter release in a single presynaptic element in the CNS. We discuss the pharmacological and physiological prospects.