Abstract
The membrane properties and morphological characteristics of premotor neurons for the trigeminal motor nucleus (MoV) in the supratrigeminal region (SupV) were investigated in neonatal rat brainstem slice preparations using whole-cell recordings and immunohistochemical techniques. Premotor neurons in the SupV were identified on the basis of the intracellular calcium concentration rise in response to electrical stimulation of the MoV using a calcium imaging system. Whole-cell recordings were made from SupV neurons that responded to MoV stimulation. We divided these neurons into two groups according to their discharge pattern in response to a 1-sec depolarizing current pulse at the resting membrane potential. High-frequency firing neurons (HF neurons) showed regular high-frequency tonic firing. Low-frequency firing neurons (LF neurons) discharged at lower frequencies and displayed stronger firing frequency adaptation than HF neurons. In some HF neurons, membrane depolarization produced a rhythmical burst discharge. Biocytin was injected to the recorded neuron through patch pipettes, and the axons of biocytin-labeled SupV neurons projected in the ventral, medial-ventral or lateral-ventral directions to the MoV and terminated extensively within the MoV. These results suggest that premotor neurons for the MoV in the SupV show physiological and morphological diversity and therefore may be related to controlling the complicated and diverse motor patterns of mastication. [J Physiol Sci. 2008;58 Suppl:S132]
