Tatsuya Tokuno

Functional Changes in Thalamic Relay Neurons After Focal Cerebral Infarct: A Study of Unit Recordings from VPL Neurons After MCA Occlusion in Rats

We evaluated neuronal and histological changes of thalamic neurons 1, 4, 7, and 14 days after middle cerebral artery (MCA) occlusion in rats. After the somatosensory evoked potentials (SEPs) were measured from the cerebral cortex, the thalamic relay neuronal activities were recorded with a glass microelectrode following repetitive electrical stimulation of the contralateral forepaw at frequencies ranging from 1 to 50 Hz. In ∼95% of the occluded rats, the ipsilateral somatosensory cortex and/or the subcortical somatosensory pathway developed infarct, resulting in SEP loss. We evaluated unit data from rats with abolished SEPs. The average firing rate of the nucleus ventralis posterolateralis (VPL) neurons in response to 25 stimulations at 30 Hz was significantly reduced to 0.1 spike/stimulus 1 day after MCA occlusion. In sham-operated rats, the same stimulation produced 0.7 spike/stimulus. The firing rate recovered to 0.4 spike/stimulus at 30-Hz stimulation 4 and 7 days after occlusion. This was followed by resuppression (0.1 spike/stimulus) 14 days after occlusion. Histological study revealed some abnormal neurons in the ipsilateral thalamus 7 days after occlusion. We were unable to find normal-shaped neurons in the VPL 14 days after occlusion. The present study demonstrates that cortical infarct produces functional and morphologic changes that gradually and progressively affect the ipsilateral thalamus, although incomplete transient recovery of somatosensory transmission may occur.

Energy metabolism in unrestrained fish with in vivo 31P-NMR

Abstract 1. 1. We evaluated changes in high energy phosphate metabolism in unrestrained freshwater loaches by in vivo 31 P-NMR. 2. 2. When dissolved oxygen was deficient, both an increase in Pi and a decrease in PCr were observed as the loach struggled. 3. 3. After pretreating the fish with an anesthetic agent, we observed the dependence of high energy phosphate metabolism on changes in dissolved oxygen. 4. 4. Under anesthetic [Pi]/[Pi] + [PCr] ratio, an index of metabolic state, was lower than without anesthesia. 5. 5. Decrease in high energy phosphate metabolism in fish during oxygen deficiency was not caused by poor oxygen supply but resulted from struggle movement due to lack of oxygen.

Electrophysiological changes in substantia nigra after striatal infarction.

The GABAergic efferent pathway from the striatum exerts inhibitory control on the substantia nigra pars reticulata (SNR) neurones. We studied sequential changes in spontaneous single-unit activities in the ipsilateral SNR 1 h, 1 day, 7 days and 14 days after striatal infarction induced by middle cerebral artery occlusion (MCAO) in rats. Compared with a sham-operated group, there was no change in the firing rate 1 h after MCAO, and one day after MCAO the mean firing rate decreased. The firing rate of SNR neurones at 7 and 14 days after MCAO was significantly reduced compared with the sham-operated group. Only two neurones (sham-operated group and 1 h after MCAO group) fired with high frequency. Histological examination revealed degeneration of the ipsilateral SNR 7 and 14 days after MCAO. Our results indicated that SNR neuronal degeneration accompanied by striatal ischaemia does not simply depend on hyperexcitation due to the activation of a disinhibition mechanism.

Changes in high-energy phosphate metabolites in loaches (cobitis biwae) during 2-phenoxyethanol anesthesia

Abstract 1. We evaluated changes in high-energy phosphate metabolism in the muscle of loaches during 2-phenoxyethanol (2-PE) anesthesia by 31 P-NMR. 2. The creatine phosphate (PCr) concentration increased while the inorganic phosphate (Pi) concentration decreased in the muscle as 2-PE anesthesia was continued, but both returned to the preanesthetic values with recovery from the anesthesia. 3. The sugar phosphate (SP) concentration also increased during anesthesia, but SP did not disappear after recovery. 4. In the muscle of loaches anesthetized with 2-PE, the phosphate metabolism was aerobic, but carbohydrate metabolism was suppressed.

Neurofunctional Changes in Thalamic Neurons After Cortical Ablation in Adult Rats: Effect of Basic Fibroblast Growth Factor upon Thalamic Neurons

Traumatic damage to cortex results in progressive degeneration in the ipsilateral thalamus. It has recently been suggested that this degeneration is attributable to neurotrophic mechanisms. We studied the functional and morphological changes in thalamic relay neurons that occurred following traumatic cortical ablation, and also studied the effects of basic fibroblast growth factor (b-FGF), one of neurotrophic factors, on these changes.

Changes in activity of substantia nigra pars reticulata neurons after middle cerebral artery occlusion in the rat

The spontaneous single unit activity of substantia nigra pars reticulata (SNR) neurons was studied in control and in ipsilateral middle cerebral artery (MCA) -occluded rats. The activity of MCA-occluded preparations was recorded in 3 groups; 1 hour, 24 hours, and 7 days after MCA occlusion. Activity was recorded extracellularly with glass microelectrodes and was analyzed using time interval histograms. In the control, half of the SNR units (47%) showed a regular firing pattern. There was no change 1 hour after MCA occlusion. After 24 hours and 7 days, however, there was increased SNR neuronal unit activity with irregular firing patterns (67% and 57%, respectively), and a slightly decreased mean firing rate. In the MCA-occluded groups, no hyperexcited neurons at all were found in the SNR. Our results indicated that SNR neuronal degeneration accompanied by striatal ischemia does not depend simply on hyperexcitation due to a disinhibition mechanism.

Energy metabolism during contraction of the first ambulatory leg of the crayfish

Abstract 1. 1. The metabolism of high energy phosphates during contraction of muscle in the first ambulatory leg of the crayfish, Procambarus clarkii, by neural stimulation was evaluated by 31P-NMR. 2. 2. When the chela nerve was stimulated, the phosphoarginine (Arg-P) concentration showed no clear change with the first five stimuli, but shortly thereafter a decrease was observed with an elevation in Pi muscle stimulation. 3. 3. The rate of Arg-P decrease was not dependent on stimulus frequency. 4. 4. The pH changes were more marked in the case of direct electrical stimulation, and reached about 80% of the initial concentration under aerobic conditions and about 95% under anaerobic conditions.