Abstract
The superior salivatory (SS) nucleus , the primary parasympathetic center for the submandibular salivary secretion, is located in the lateral reticular formation of the medulla oblongata. Many neuroanatomical studies suggest that the neurons innervating SS neurons are distributed in the forebrain (higher centers) and lower brainstem (lower centers). Recently, we have electrophysiologically shown that many SS neurons receive GABAergic and glycinergic inputs from higher and lower centers. In the present study, we aimed to examine the distribution of GABAergic neurons innervating SS neurons. We carried out double-labeling of the GABAergic neurons projecting to SS neurons by injection of retrograde fluorescent tracer, FluoroGold (2%, 0.025 μl), into SS nucleus, and by immunohistochemical staining for glutamic acid decarboxylase, a GABA synthetic enzyme. In the higher centers, double-labeled neurons were mainly observed in the lateral hypothalamic area and central nucleus of the amygdala. In the lower centers, double-labeled neurons were mainly found in the parabrachial nucleus, nucleus of the solitary tract and its surrounding reticular formation. These findings imply that these higher and lower centers are involved in the inhibitory salivary control. [J Physiol Sci. 2008;58 Suppl:S154]
