[Influence of glutamate and NMDA-receptor antagonist MK-801 on the electric activities of pain-excitation neurons in the nucleus accumbens of rats].

The experiment explored the influence of glutamic acid (Glu) and the NMDA-receptor antagonist dizocilpine maleate (MK-801) on the pain-evoked responses of pain-excitation neurons (PEN) in the nucleus accumbens (NAc) of rats. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. The discharges of PEN in NAc were recorded by glass microelectrode. We observed the influence of intracerebroventricular (icv) injection of Glu and microinjection of MK-801 into the NAc on the noxious stimulation-evoked activities of PEN in NAc. The results showed that the noxious stimulation potentiated the electric activities of PEN in NAc. Intracerebroventricular injection of Glu (10 nmol/10 microl) increased the frequency of the discharge of PEN evoked by the noxious stimulation in NAc, the Glu-induced response was blocked by the injection of MK-801 (1.0 nmol/0.5 microl) into NAc. MK-801 partly inhibited the response of PEN upon the noxious stimulation. It is therefore suggested that the facilitatory effect of Glu on PEN response in NAc to the noxious stimulation is mediated by NMDA receptors, and that Glu and NMDA receptors are involved in the modulation of nociceptive information transmission in the NAc.