The effect of internal capsule and/or thalamic sensory nucleus stimulation on deafferentation hyperactivity in relation to pain relief - Experimental studies in the cat -

The effect of electrical stimulation of the internal capsule (IC) or sensory thalamic nucleus (VPM) on neuronal activity in the subnucleus caudalis of the spinal trigeminal nucleus (STNcd) was examined electrophysiologically in the cat. The nociceptive neuronal firing in the STNcd was suppressed by the facilitation of the non-opiate pain inhibitory system, such as electrical stimulation of the IC or VPM of either side. High amplitude spontaneous and continous neuronal hyperactivity (deafferentation hyperactivity: DH), which was provoked in the left STNcd after complete ablation of the left Gasserian ganglion, was conspicuously suppressed by electrical stimulation of the IC of either side (rt. IC stimulation: 30/60; It. IC stimulation: 13/33), as well as by VPM stimulation of either side (rt. VPM stimulation: 5/13; It. VPM stimulation: 5/9). DH, similar to that provoked in the left STNcd after ganglionectomy, was found to spread to the right sensory thalamic nucleus. Twelve neurons with DH were identified in right VPM and nucleus centralis medialis. As many as nine of these twelve neurons were distributed in the marginal area of the VPM. DH in the right thalamus was also suppressed by the stimulation of the IC on either side, however, the suppressive effect was predominant with ipsilateral IC stimulation. These results are compatible with the clinical experience of relief of deafferented (deafferentation) pain by electrical stimulation of the IC or sensory thalamic nucleus (VPM, VPL). After detailed analysis and considerations, it was supposed that this experiment supports the postulated theory that not only deafferented pain but also afferent pain is relieved by the facilitation of the non-opiate pain inhibitory system including the IC and/or the sensory thalamic nucleus

Expression of aggrecan components in perineuronal nets in the mouse cerebral cortex

Specific regions of the cerebral cortex are highly plastic in an organism’s lifetime. It is thought that perineuronal nets (PNNs) regulate plasticity, but labeling for Wisteria floribunda agglutinin (WFA), which is widely used to detect PNNs, is observed throughout the cortex. The aggrecan molecule—a PNN component—may regulate plasticity, and may also be involved in determining region-specific vulnerability to stress. To clarify cortical region-specific plasticity and vulnerability, we qualitatively analyzed aggrecan-positive and glycosylated aggrecan-positive PNNs in the mature mouse cerebral cortex. Our findings revealed the selective expression of both aggrecan-positive and glycosylated aggrecan-positive PNNs in the cortex. WFA-positive PNNs expressed aggrecan in a region-specific manner in the cortex. Furthermore, we observed variable distributions of PNNs containing WFA- and aggrecan-positive molecules. Together, our findings suggest that PNN components and their function differ depending on the cortical region, and that aggrecan molecules may be involved in determining region-specific plasticity and vulnerability in the cortex. Keywords: Aggrecan, Brain region-specific, Chondroitin sulfate proteoglycan, Extracellular matrix, Perineuronal nets, Plasticit