Distribution of GABAergic and glycinergic premotor neurons projecting to the facial and hypoglossal nuclei in the rat

Abstract

The distribution of inhibitory premotor neurons for the facial and hypoglossal nuclei was examined in the lower brainstem of the rat. A retrograde axonal tracing method with the fluorescent tracer, tetramethylrhodamine dextran amine (TMR-DA), was combined with immunofluorescence histochemistry for glutamic acid decarboxylase (GAD), i.e., the enzyme involved in gamma-aminobutyric acid synthesis, or glycine. In the rats injected with TMR-DA unilaterally into the facial or hypoglossal nucleus, the distribution of TMR-DA-labeled neurons showing GAD-like immunoreactivity (GAD/TMR-DA neurons) was essentially the same as that of TMR-DA-labeled neurons displaying glycine-like immunoreactivity (Gly/TMR-DA neurons). The distributions of GAD/TMR-DA and Gly/TMR-DA neurons in the rats injected with TMR-DA into the facial nucleus were also similar to those in the rats injected with TMR-DA into the hypoglossal nucleus. These neurons were seen most frequently in the lateral aspect of the pontine reticular formation, the supratrigeminal region, the dorsal aspect of the lateral reticular formation of the medulla oblongata, and the reticular regions around the raphe magnus nucleus and the gigantocellular reticular nucleus pars alpha, bilaterally with a slight dominance on the side ipsilateral to the injection site. A number of GAD/TMR-DA and Gly/TMR-DA neurons were also seen in the oral and interpolar subnuclei of the spinal trigeminal nucleus, bilaterally with a slight ipsilateral dominance. In the rats injected with TMR-DA into the facial nucleus, GAD/TMR-DA and Gly/TMR-DA neurons were also encountered in the paralemniscal zone of the midbrain tegmentum bilaterally with an apparent dominance on the side contralateral to the injection site. A large part of these inhibitory premotor neurons for the facial and hypoglossal nuclei and the excitatory ones may constitute premotor neuron pools common to the orofacial motor nuclei implicated in the control of integrated orofacial movements.

Changes in Inhibitory Amino Acid Release Linked to Pontine-Induced Atonia: AnIn VivoMicrodialysis Study

“…Neurons containing inhibitory amino acids have been found in the hypoglossal nucleus (Takasu et al, 1987;Aldes et al, 1988) and spinal ventral horn (Shupliakov et al, 1993). On the other hand, immunohistochemistry combined with retrograde tracer injection technique revealed that GABAergic and glycinergic neurons in the nucleus gigantocellularis ␣ and ventralis in the rat, which corresponds to the nucleus magnocellularis (NMC) in the cat, project to the spinal ventral horn (Holstege, 1991;Holstege and Bongers, 1991;Ellenberger, 1999) and hypoglossal nucleus (Li et al, 1997). GABAergic neurons in the PIA are reported to project to the hypoglossal nucleus (Li et al, 1997).…”

“…On the other hand, immunohistochemistry combined with retrograde tracer injection technique revealed that GABAergic and glycinergic neurons in the nucleus gigantocellularis ␣ and ventralis in the rat, which corresponds to the nucleus magnocellularis (NMC) in the cat, project to the spinal ventral horn (Holstege, 1991;Holstege and Bongers, 1991;Ellenberger, 1999) and hypoglossal nucleus (Li et al, 1997). GABAergic neurons in the PIA are reported to project to the hypoglossal nucleus (Li et al, 1997). Although inhibitory amino acid containing neurons are found in the PIA (Rampon et al, 1996;Maloney et al, 2000), the neuronal type projecting to the spinal cord from this region (Kuypers and Maisky, 1975;Tohyama et al, 1979;Matsuyama et al, 1999) remains unclear.…”

Rhythmic Whisking by Rat: Retraction as Well as Protraction of the Vibrissae Is Under Active Muscular Control

“…4Q). Inhibitory interneurons that contact the facial motoneurons have been reported (Li et al 1997). An additional tonic input that is required to bias the motoneurons that are driven by inhibitory input could be provided by serotonergic projections (Dolphin and Greengard 1981;McCall and Aghajanian 1979).…”

Synaptic Control of Motoneuronal Excitability

“…Thus hypoglossal premotor neurons are ventrolateral and dorsolateral in the medullary reticular formation (122,297,1263), and the majority of trigeminal and facial premotor neurons are in the pontomedullary and parvicellular reticular formations (482,535,850,1263). Some of these premotor neurons are GABAergic, glycinergic, or glutamatergic (738,739,1210,1277,1278). In addition to these regions, a smaller number of premotor neurons to trigeminal, facial, and hypoglossal nuclei are located in 1) pontine nuclei (Kölliker-Fuse; parabrachial nucleus; and trigeminal, facial, and hypoglossal nuclei); 2) periaqueductal gray of the midbrain (facial and hypoglossal nuclei); 3) periambigual region (hypoglossal and facial nuclei); 4) vestibular nuclei (facial nucleus); 5) gigantocellular reticular nucleus (all 3 nuclei); and 6) paralemniscal zone in the lateral midbrain and external cuneate nucleus (facial nucleus) (175, 297, 474, 482, 544, 737-739, 935, 1209, 1263, 1404).…”