Somatosensory & motor research
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The present study analyzes the activity of 120 neurons recorded in the two ventro-postero-medial (VPM) nuclei of the thalamus in a rat model of trigeminal neuropathic pain. Twenty-eight rats were tested 2 weeks after a chronic constriction injury (CCI) of the infraorbital nerve (IoN). These animals exhibited violent pain-related reactions to extremely weak mechanical stimuli applied to the lesioned and, to a lesser extent, unlesioned IoN territories. ⋯ In contrast to the VPMn neurons, the RFs of both the VPMc and VPMi neurons included two vibrissae at least, and were occasionally discontinuous and multimodal, including both vibrissae and cutaneous areas for VPMc units. The bilateral changes in VPM responsiveness and in behavior suggest the involvement of central processing of sensory information, which are set off by the CCI-IoN. The putative mechanisms and functional implication of the changes in the VPM neuronal activities are discussed.