A continuous rhythmic discharge in the subthalamic nucleus (STN), lateral habenular nucleus, and ventral tegmental area (VTA) is associated with tremor in cats lightly anesthetized with barbiturate. The pontine raphe nuclei centralis superior and inferior also show barbiturate dependent slow wave and unitary activity. Stimulation of the raphe region produces evoked potentials and synchronization of the oscillatory activity in STN and VTA. The latency of the evoked response is shortest in STN. Extensive raphe lesions abolish the rhythmic activity in STN and VTA, but lesions which do not completely destroy nuclei centralis superior and inferior are not effective. In single cell recordings 81% of 142 cells in the pontine raphe region and medial reticular formation are inhibited following VTA stimulation. Fifty-four percent of 129 cells in the same region were inhibited when tested with STN stimulation. Forty-seven raphe paramedian reticular formation cells showed convergence of inhibitory input from STN, VTA, and contralateral sciatic nerve (Group II and III fibers). Depletion of serotonin with rho-chlorophenylalanine did not affect the appearance of barbiturate rhythmic activity. It is concluded that the pontine raphe region is not essential for maintenance of the oscillatory activity in STN and VTA, and that the raphe region is on the output side of the system.

Animals↗

PubMedDate not supplied

The effects of arm position on central spread of local anesthetics and on quality of the block with axillary brachial plexus block.

BACKGROUND AND OBJECTIVES: Spread of local anesthetic solution in axillary brachial plexus block is thought to be influenced by the position of the arm and the use of compression maneuvers. We investigated how these two factors affected central local anesthetic spread and block quality. METHODS: Radiographic spread of local anesthetic was studied in 80 adult patients. They received mepivacaine mixed with contrast agent through an indwelling catheter with the arm abducted to either 0 or 90 degrees , and with or without local digital compression. Central and peripheral spread of the contrast agent was evaluated with anteroposterior radiographs of the axilla. Block quality was studied in a separate series of 70 adult patients. They received mepivacaine with the arm abducted 0 degrees or 90 degrees . The degree of sensory and motor block was assessed 20 minutes after the injection. RESULTS: Arm position at 0 degrees abduction promoted central spread of the contrast agent. Although digital compression suppressed peripheral spread effectively, it did not improve the central spread of the solution. Sensory block was comparable in all terminal nerves of the arm in both arm positions, whereas motor block of the radial nerve was promoted with no abduction. CONCLUSIONS: The central spread of local anesthetics is facilitated by injection without abduction of the arm but not by the use of compression at the injection site. This, however, did not alter the quality of the block.

Adult↗

PubMedDate not supplied

Emotional slow negative potential shift (CNV) in the thalamus.

In order to know the functional relationship between CNV recorded at the vertex and activity of the thalamic nucleus, the CNV at the vertex and the intrathalamic slow potentials responding to an S1-S2-R paradigm were recorded during thalamotomy under local anesthesia. It might be concluded that the activity of the medial thalamus and medial parts of the subthalamic area not only generate slow potential shifts corresponding to S1-S2-R, but also play an important role in controlling the CNV at the vertex.

Brain Mapping↗

PubMedDate not supplied

Neurosciences for study of coma.

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Brain Injuries↗

PubMedDate not supplied

Impaired hippocampal plasticity in experimental chronic hydrocephalus.

Schaffer collateral responses recorded from CA1 pyramidal cell layers in the hippocampus were analysed in kaolin-induced hydrocephalic rats. Other features of this rat model of chronic hydrocephalus were evaluated from measurements of the intracranial pressure, Na-fluorescein migration from the ventricle to the cerebral parenchyma, and behavioural changes. The results indicated that: (1) the conduction velocity of the Schaffer collaterals was unchanged; (2) the threshold to elicit population spikes was decreased; (3) the paired-pulse facilitation of EPSP tended to increase; (4) the paired-pulse inhibition of population spikes was unchanged; and (5) the long-term potentiation of population spikes was clearly attenuated in the hydrocephalic rats. The changes seen in the long-term potentiation were less pronounced in rats which underwent kaolin injection but did not develop hydrocephalus. The above findings suggest that disturbance in the postsynaptic integration processes, rather than axonal conduction or synaptic transmission, are more important for the production of the neurological deficits seen in chronic hydrocephalus. Electron microscopic observations supporting this inference are also briefly described.

Animals↗