| Research Abstract |
We found that electrical microstimulation of the jaw region of the rat striatum (SJR) activates the jaw-opening and tongue-protruder muscles, but not the jaw-closing, tongue-retractor, or facial muscles (Neurosci. Lett. 253 : 79-82, 1998 ; Brain Res., 893 : 282-286, 2001). Such effect can be induced even after removal of the cerebral cortex, but not after destruction of striatal neurons by injecting kainic acid into the SJR. Therefore, the effect of the stimulation of the SJR is considered to be produced by the stimulation of striatal neurons in the SJR ; it is not the effect of stimulation of corticofugal fibers through the SJR. In the present study, we examined the sites of origin of cortico-SJR fibers by the retrograde labeling. The SJR, identified by electrical microstimulation, was injected electrophoretically with cholera toxin B subunit. Retrogradely labeled neuronal cell bodies were detected mainly in the following regions : 1) Cerebral cortex : frontal cortical regions, includ
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ing the motor and somatosensory areas, and insural cortical regions. Labeled cell bodies were distributed to layers II, III, V and VI of these cerebral cortical regions ; 2) Thalamus : central medial nucleus, paracentral nucleus, parafascicular nucleus ; 3) Amygdala : basolateral nucleus ; 4) Substantia nigra pars compacta ; 5) Dorsal raphe nucleus. Termial labeling was also seen in the globus pallidus, entopeduncular nucleus and substantia nigra pars reticulata. In the cerebral cortex ipsitateral to the injection, there existed two foci of retrograde labeling : One focus was centered on the lateral part of the sensorimotor area, while the other on the insular cortical area around the middle cerebral artery. These foci appeared to correspond to the reported two cortical areas, where two different types of rhythmical jaw movements were induced by repetitive electrical stimulation (Jap. J. Oral Biol., 32 : 57-68, 1990). It is also well known that the stimulation of the basolateral amygdaloid nucleus induces jaw-movements. Less
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