Responses of somatosensory cortical neurones to tooth pressure and their modulation by transient mouth opening in the cat.

One hundred and thirty two cortical neurones sensitive to mechanical tooth stimulation were detected from the caudal part of the coronal gyrus of the cat. They responded to transient mechanical stimulation of the tooth (TMTst) with initial burst discharges (latency; 14.9 +/- 8.7 ms) and sequential suppression of spontaneous discharges (duration; 218 +/- 142 ms). They also fired strongly at the onset and removal of sustained mechanical stimulation of the tooth (SMTst) with both on and off responses, but the responses for the duration of stimulation were indistinguishable from the spontaneous discharge level. Conditioning stimulation by transient mouth opening (TMOst) inhibited the on and off responses elicited by tooth pressure in 13 (56.5 per cent) of the 23 cortical neurones and in 16 (88.9 per cent) of the 18 neurones tested, respectively. On reversing the conditioning-test sequence, the response elicited by TMOst was inhibited by the onset and removal of SMTst in 12 (52.2 per cent) of the 23 neurones and in 8 (44.4 per cent) of the 18 neurones tested, respectively. The inhibitory period ranged from 50 to 250 ms.