The distribution and functional properties of nociceptive neurons with masseteric input in the cat thalamus

Abstract

I investigated the distribution and functional properties of nociceptive neurons responding to masseteric nerve stimulation in the nucleus ventralis posteromedialis proper (VPM) and intralaminar (IL) nuclei of the thalamus. The activity of single thalamic neurons in cats anesthetized with urethane-chloralose was assessed extracellularly. Thirty-two neurons with masseteric input observed around the periphery of the posterior half of the VPM responded to noxious mechanical stimulation. They were therefore considered to be nociceptive specific (NS) and wide dynamic range (WDR) neurons. Twenty-six neurons were found in the nuclei parafascicularis and centralis lateralis of the IL nuclei. These finding suggest that masseteric input, such as masseteric pain information, is conveyed to the cortex via NS and WDR neurons, and IL nociceptive neurons.