Receptive field properties of thalamo-cortical taste relay neurons in the parvicellular part of the posteromedial ventral nucleus in rats

Summary

Twenty-five taste and 35 mechanoreceptive neurons were recorded from the parvicellular part of the posteromedial ventral nucleus (VPMpc) in rats. Among them, 14 (56%) of the taste and 7 (18.4%) of the mechanoreceptive neurons were antidromically activated from the cortical taste area (CTA) with a latency of 1–4 ms and identified as thalamocortical (TC) relay neurons. No significant differences were evident in the receptive field properties or in the location in the VPMpc between the TC and non-TC neuron groups. Two classes of TC neurons were recognized: one class consisted of neurons which were most excited by NaCl among the four basic taste stimuli with receptive fields (RFs) confined to a part of the oral cavity, e.g. the anterior tongue, and the other class contained neurons which were most excited by sucrose or HCl, with RFs over a wide area of the oral cavity. Both the TC and non-TC neurons showed similar effects of CTA stimulation: post-stimulus time histograms revealed a long lasting inhibition followed by a rebound facilitation of spontaneous discharge.