Showing papers on "Cuneate nucleus published in 1967"

Micro‐iontophoretic studies on neurones in the cuneate nucleus

Abstract: 1. Cuneate cells in anaesthetized cats were strongly excited by L-glutamate, and somewhat less by D-glutamate; cells which receive afferents from hair receptors were particularly sensitive. 2. Glutamate could be used to demonstrate post-synaptic inhibitory inputs from the dorsal column, the medial lemniscus and the frontal cortex. 3. Many cuneate cells were also strongly excited by adenosinetriphosphate (ATP); this was probably due to the chelating action of ATP, as citric acid was also quite effective. 4. γ-Aminobutyric acid (GABA) readily blocked all forms of spontaneous and evoked activity, except antidromic invasion of cuneothalamic neurones; cells which receive proprioceptive afferents were particularly sensitive to GABA. Glycine had a comparable effect. 5. Acetylcholine (ACh), catecholamines, histamine, 5-hydroxytryptamine (5-HT) and an extract containing substance P mostly had only weak depressant actions. Cholinergic and mono-aminergic mechanisms are probably not very significant in the cuneate. 6. These results are consistent with the possibility that glutamate and GABA (or glycine), or some closely related compounds, are the main excitatory and inhibitory transmitters in the cuneate nucleus. 7. If ATP is released from afferent nerve endings, it could also play a significant role in excitation.

Presynaptic and postsynaptic inhibition of transmission of somatic afferent volleys through the cuneate nucleus during sleep.

Abstract: Durante i movimenti rapidi oculari caratteristici della fase desincronizzata di sonno si osserva una depressione fasica della risposta lemniscale alla stimolazione di fibre cutanee. Questa modulazione ipnica della risposta lemniscale e dovuta a meccanismi di inibizione presinaptica e postsinaptica.

Cortical responses to paired stimuli applied peripherally and at sites along the somato‐sensory pathway

Abstract: 1. Experiments have been performed on animals anaesthetized with various anaesthetics to determine the responsiveness of the cortex to the second of a pair of identical stimuli applied at three sites along the sensory pathway, i.e. to the periphery, the medial lemniscus and to thalamocortical fibres. 2. It has been found that in deeply anaesthetized animals the mass response recorded from the cerebral cortex to the second of a pair of peripheral or lemniscal stimuli became reduced in size if the interval between the stimuli was 30-500 msec. If the interval was less than 30 msec for peripheral stimuli or between 10 and 30 msec for lemniscal stimuli responses were not obtained to the second stimulus. This was found to be a basic pattern which could be modified in animals less deeply anaesthetized. In these animals, periods of relatively increased responsiveness were seen after peripheral stimulation. 3. The post-synaptic responses recorded from the ventrobasal thalamus showed the same behaviour to the second of a pair of peripheral stimuli as did the cortex both as regards size and latency of the responses. 4. The post-synaptic responses recorded from the cuneate nucleus rarely showed any reduction in size unless the separation between the stimuli was 10 msec or less; even at intervals as low as 3 msec there was no increase in the latency of the response. 5. When a pair of stimuli were applied to thalamocortical fibres, a different pattern of cortical responsiveness was found. At the time the cortical response to stimulation at pre-thalamic sites was reduced or abolished, the response to stimulation at post-thalamic sites was unaltered or increased in size. 6. Finally an attempt was made to correlate the mass response recorded from the cortical surface and the activity of single cortical cells. Two types of cell could be distinguished in the rat. Those lying from 0·35 to 1·2 mm deep in the cortex showed a response pattern, to paired stimuli, closely resembling that of the cortical mass response. Others situated deeper in the cortex were found which had a very long absolute unresponsive time, from 50 to 80 msec and a very long relative unresponsive time of 1 sec.