[Reactions of the somatosensory cortex neurons, activated by nociceptive afferents during stimulation of substantia nigra in experiment].
In cats, we studied the influences of stimulation of the Substantia Nigra (SN) on postsynaptic processes evoked in neurons of the somatosensory cortex by stimulation of nociceptive (intensive stimulation of the tooth pulp) and non-nociceptive (moderate stimulation of the infra orbital nerve and ventroposteromedial (VPM) nucleus of the thalamus) afferent inputs. Seven cells activated exclusively by nociceptors and ten cells activated by both nociceptive and non-nociceptive influences (hereafter, nociceptive and convergent neurons, respectively) were recorded intracellularly. In neurons of both groups, responses to nociceptive stimulation (of sufficient intensity) looked like in EPSP-spike-IPSP (the letter of significant duration, up to 200-300 msec) complex. Conditioning stimulation of the SN which preceded test stimulus applied to the tooth pulp or VPM nucleus by 100 to 700 msec, induced 40-60% decrease of the IPSP amplitude only, while maximal effect of influence, in both cases, was noted within intervals of 300-700 msec between conditioning and test-stimulus. During stimulation of the SN, dopamine released via receptor and second messengers, provides postsynaptic modulation of GABA-ergic system, decreasing the IPSP amplitude, which occurs after stimulation of both the tooth pulp and VPM thalamic nucleus. This process may be realized through either pre- or postsynaptic mechanisms.
D000818:Animals; D002415:Cats; D004298:Dopamine / Q000378:metabolism; D004567:Electrodes, Implanted; D009474:Neurons / Q000378:metabolism*; D009619:Nociceptors / Q000378:metabolism*; D010146:Pain / Q000378:metabolism*; D010812:Physical Stimulation / Q000379:methods*; D013003:Somatosensory Cortex / Q000378:metabolism*; D013378:Substantia Nigra / Q000378:metabolism*
D004298:Dopamine