[Postsynaptic reactions of cerebral cortex neurons, activated by nociceptiveafferents during stimulation of Locus Coeruleus].
In cats, we studied the influences of stimulation of the Locus Coeruleus 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 infraorbital nerve and ventro-posteromedial (VPM) nucleus of the thalamus) afferent inputs. Seven cells activated by both exclusively by nociceptors and ten cells activated by both nociceptive and non-nociceptive influences (hereafter, nociceptive and convergent neurons, respectively) were recorded intracellular. 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 LC which preceded test stimulus applied to the tooth pulp or VPM nucleus by 100 to 800 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 LC, noradrenaline 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.
I. Beritashvili Institute of physiology, Tbilisi, Georgia.
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Labakhua
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Janashia
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Gedevanishvili
D000818:Animals; D002415:Cats; D004567:Electrodes, Implanted; D008125:Locus Coeruleus / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation / Q000379:methods*; D013003:Somatosensory Cortex / Q000503:physiopathology*