Abstract
The afferent fibers in the vagus nerve transmit visceral information encoded as varying firing frequency to the second-order neurons in the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (DMX) in the solitary complex (SC). Excitatory synaptic transmission between primary afferents and second-order neurons shows distinct short-term plasticity depending on the postsynaptic cell type, which is also related to distinct decay rate in response to high-frequency repetitive stimulation of the afferents (Yamamoto et al., 2006). To reveal the distinct synaptic mechanisms that underlie the different short-term plasticity, we estimated the release probability, quantal EPSC size and the number of release sites based on the mean and variance of the EPSC amplitude recorded at various extracellular Ca2+ concentrations in brainstem slices from young Wistar rats. The results indicate that the release probability is negatively correlated with the paired-pulse ratio and that the number of release sites is negatively correlated with the release probability, suggesting that release probability is the primary determinant of the short-term plasticity and the subsequent frequency-dependent filtering properties in the SC. [J Physiol Sci. 2008;58 Suppl:S98]
