Neural activities in the substantia nigra modulated by stimulation of the orofacial motor cortex and rhythmical jaw movements in the rat.
Neurons related to jaw movements in the substantia nigra pars reticulata were explored by examining changes in their neural activities in response to electrical stimulation of the orofacial sensorimotor cortex and during rhythmical jaw movements induced by mechanical stimulation applied to the oral cavity in the rat. Out of 80 neurons tested, 59 showed changes in their firing patterns of activities in response to the electrical stimulation of the cortex. The responding neurons were mainly located in the dorsolateral part of the substantia nigra pars reticulata. The substantia nigra pars reticulata neurons showing responses were classified into the following five types according to their response patterns: (1) an inhibition preceded by an early excitation and followed by a late excitation (n = 26), (2) an inhibition preceded by an early excitation but not followed by a late excitation (n = 7), (3) an inhibition not preceded by an early excitation but followed by a late excitation (n = 2), (4) an inhibition without early or late excitations (n = 7) and (5) an excitation without an inhibition (n = 17). Out of 18 neurons responding to the cortical stimulation, 11 (61.1%) increased or decreased their neural activities during rhythmical jaw movements. Some of these neurons had a projection to the lateral part of the superior colliculus (n = 5) and/or to the parvicellular reticular formation (n = 2). These results provide first neurophysiological evidence for neurons in the dorsolateral part of the substantia nigra pars reticulata with inputs from and outputs to the areas related to jaw movements. These neurons may participate in the control of jaw movements in the rat.
Nishimuta
K
K
Section of Oral Neuroscience, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Sasamoto
K
K
Ninomiya
Y
Y
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D007568:Jaw / Q000294:innervation* / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000502:physiology*