Abstract
The superior salivatory (SS) nucleus consists of a group of parasympathetic preganglionic neurons which innervate targets such as the submandibular and sublingual salivary glands, and anterior region of the tongue. We studied the properties of the synaptic inputs to SS neurons supplying the different targets in neonatal Wistar rats (4-8 days old). The SS neurons supplying the salivary glands and tongue were labeled by retrograde axonal transport of a fluorescent dye. Using a whole-cell patch-clamp technique, the EPSCs and IPSCs were recorded from labeled cells in brainstem slices (200 μm). Whole-cell currents were evoked by electrical stimulation of tissue surrounding the cell. To optimize the positioning the stimulating electrode, dendrite morphology of the SS neurons was examined by Neurobiotin. SS neurons have 3-5 primary dendrites that extend 200-780 μm in neurons supplying the salivary glands and 120-530 μm in neurons supplying the tongue. Robust currents were usually obtained at a few points 100-400 μm from the soma. EPSCs were mediated by NMDA and non-NMDA glutamate receptors. IPSCs were mediated by GABAA, and glycine receptors. In SS neurons for the salivary glands, the ratio of the NMDA component to total EPSCs was larger than that of non-NMDA component, and the ratio of the GABAA component to the total IPSCs was larger than that of the glycine component. The characteristics of the excitatory and inhibitory inputs may be involved in determining the firing properties of the SS neurons supplying the salivary glands and tongue. [Jpn J Physiol 54 Suppl:S203 (2004)]
