Ascending pathways mediating cardiovascular signals to the ventral posterior lateral nucleus of thalamus in the cat / 全日本鍼灸学会雑誌

Neuronal activities in the ventral posterior lateral nucleus (VPL) of the cat thalamus were recorded extracellularly using the multimicroelectrode system. In spontaneous activities, some neurons received information from structures related to cardiovascular movement and also from peripheral somatic receptive fields (Rfs). These unitary activities were synchronized with heart beat, therefore they are called as heart beat (HB) discharges. This phenomenon may be concerned with referred pain. Thus, some VPL neurons appear to relay cardiovascular information to the cerebral cortex. The characteristics of 39 HB units were determined by mechanical stimulation such as bending hair, tapping, pinching and joint movement. To investigate the ascending pathways, transection of vagi and partial spinal cord lesions at the cervical level were performed. HB activities were unaffected by bilateral vagotomy. Some of the HB activities disappeared following partial cordotomy of the lateral portion of the ventrolateral funiculus ipsilateral to the receptive field. However, evoked responses to electrical stimulation applied to the HB Rfs persisted. After the remaining cord was severed, the evoked responses vanished. These results show that afferent signals of HB activities and evoked responses to electrical stimulation appear to ascend through different pathways and converge at the thalamic level.

Ascending pathways of skin and deep information projecting to the ventral posterior lateral nucleus of thalamus in the cat / 全日本鍼灸学会雑誌

In acupuncture, the typical sensation induced by insertion of a needle into the muscle that called “De Qi” is essential to induce acupuncture analgesia. The effect of acupuncture analgesia may depend on the deep afferents rather than to the cutaneous ones at the acupuncture point. The ascending pathways conveying these skin and deep afferents project to the ventral posterior lateral nucleus (VPL) of thalamus, one of the thalamic relay nuclei projected to the cerebral cortex, were examined by spinal cord lesion at the cervical level with observation of the responses evoked by electrical stimulation applied selectively to the skin and deep tissues.<BR>Neuronal discharges were recorded extracellularly from the VPL using the multimicroelectrode technique. After spontaneous neuronal activities were recorded, the receptive fields and characteristics were determined by applying some kinds of mechanical stimulation to the receptive field. The skin and deep structures were then selectively stimulated using a pair of stainless steel needles and insulated needles except for tips. Units were classified for skin units, deep units, and skin-deep units according to the responses to the electrical stimulation. Responses were elicited in some neurons following to both skin and deep stimuli. The latency of response elicited by electrical stimulation applied to the deep structure was slightly shorter than that of the skin structure. The recording sites for deep units were located more rostrally in the dorsal region of the VPL than that for the skin units.<BR>The afferents of some skin-deep neurons from both skin and deep structures were ascended through different pathways in the spinal cord. The skin and deep afferents were found to converge at the thalamic level.