Abstract
We showed the excitatory (glutamate) and inhibitory (GABA and glycine) synaptic inputs to the superior salivatory (SS) neurons innervating the submandibular salivary glands and tongue. However, the relationships between the higher and lower centers in the synaptic inputs have not yet been examined. In the present study, we studied electrophysiologically the inhibitory synaptic inputs in brainstem slices obtained from normal and decerebrate rats. The SS neurons were labeled by retrograde axonal transport of a fluorescent dye. Whole-cell patch-clamp recordings were made from the labeled neurons. The currents were evoked by agonists (GABA and Glycine) perfusion, and electrical stimulation near the recording cell. After decerebration, agonists perfusion induced larger currents, but their decay time constant were not altered as compared with those of normals. This increase may result from receptor up-regulation at postsynaptic membrane. By electrical stimulation, in 83% (n=34/41) neurons, enhanced IPSCs were evoked, suggesting that the neurons have the inhibitory inputs from both the higher and lower centers. In 17% neurons (n=7/41), no IPSCs were evoked, suggesting that the neurons have only the descending inhibitory inputs from the higher centers. It is suggested that all SS neurons have the descending inhibitory synaptic inputs from the higher centers. [J Physiol Sci. 2006;56 Suppl:S164]
