THE DOMINANT CLASS OF SOMATOSENSORY NEURON RECORDED IN THE SPINAL DORSAL BORN OF AWAKE SHEEP HAS WIDE DYNAMIC-RANGE PROPERTIES

In order to investigate the properties of dorsal horn neurones in the absence of the distorting influences of anaesthesia, preparative surge ry, prior training or excessive restraint, recordings have been made i n sheep chronically prepared for single-cell recording. Within the lim itationss of sampling error of dorsal horn neurones with cutaneous rec eptive fields, the cell type most frequently encountered had wide dyna mic range (WDR; convergent; multireceptive) properties; these accounte d for 59% of the 46 neurones that were examined in detail. High-thresh old mechanoreceptive (nocispecific) and low-threshold mechanoreceptive neurones formed 11% and 30% of the sample, respectively. These and ot her data indicate that under normal physiological conditions in the aw ake state, many spinal neurones do indeed have WDR properties, implyin g that these cells have an important function in nociceptive processin g.