Elucidation of Central Analgesic Mechanism during Cavity Preparations -Channel Analysis of Osmosensitive Neurons within the Nucleus of the Solitary Tract-

1.Electrophysiological recordings were carried out in the whole cell current-clamp configuration on the Nucleus of the Solitary Tract(NTS)of the rat.The perfusion was changed from isotonic aCSF to hypertonic or hypotonic solutions，or negative pressure or positive pressure were applied to the inside of whole-cell patch pipettes and impulse frequency membrane potential and membrane resistance were recorded。And SA channel blocker(GdCl3)or Cl-channel blocker(SITS)was added to the perfusate and the changes of the responses were recorded.2。Single electrical stimuli were delivered to the caudal part of the Spinal Trigeminal Nucleus and evoked currents were recorded through the whole-cell patch pipettes in the NTS。5-HT was added to the perfusate and the changes of the evoked currents were examined.3。These results suggest that(1)The osmosensitive neurons in the NTS，respond to the phased mechanical deformation，have stretch activated and stretch inactivated ion channels.(2)The extracellular hyperosmotically evoked cell shrinkage causes the stronger probability of the open-(SA Cation Channels).(3)The extracellular hyposmotically evoked cell swelling is relevant to the SA Cl I D 1-i-D 1 chactivity.(3)The extracellular hyposmotically evoked cell swelling is relevant to the SA Cl I D1-it channels。

1. Electrophysiological recordings were carried out in the whole cell current-clamp configuration on the Nucleus of the Solitary Tract (NTS) of the rat. The perfusion was changed from isotonic aCSF to hypertonic or hypotonic solutions, or negative pressure or positive pressure were applied to the inside of whole-cell patch pipettes and impulse frequency membrane potential and membrane resistance were recorded. And SA channel blocker (GdCl3) or Cl- channel blocker (SITS) was added to the perfusate and the changes of the responses were recorded.2. Single electrical stimuli were delivered to the caudal part of the Spinal Trigeminal Nucleus and evoked currents were recorded through the whole-cell patch pipettes in the NTS. 5-HT was added to the perfusate and the changes of the evoked currents were examined.3. These results suggest that(1) The osmosensitive neurons in the NTS, respond to the phased mechanical deformation, have stretch activated and stretch inactivated ion channels.(2) The extracellular hyperosmotically evoked cell shrinkage causes the stronger probability of the open- (SA cation channels).(3) The extracellular hyposmotically evoked cell swelling is relevant to the SA ClィイD1-ィエD1 channel activity.(4) The caudal part of the NTS receive the incoming signals from the caudal part of the Spinal Trigeminal Nucleus.(5) The neurotransmitter of the synapse, that connects from the caudal part of the Spinal Trigeminal Nucleus to the NTS, is possibly 5-HT.