Fig. 3

Activation of LC:SC suppresses the firing frequency of WDR neurons in CCI mice. A Experimental protocol for AAV injection and pain threshold test. i.p.: intraperitoneal injection. i.t.: intrathecal injection. B Schematic representation of the Gq-DREADD protocol targeting LC:SC. C Experimental protocol for noxious pinch or non-noxious brush and 1 g von Frey applied to the ipsilateral hind paw during spinal drug application. Original traces of pinch or brush and 1 g von Frey responses from WDR neurons during application of CNO (i.p., 3 mg/kg) or CNO (i.p., 3 mg/kg) + Yohimbine (i.p., 0.1 μg/kg). D There was no obvious change of the spontaneous discharge of the WDR neuron in CCI mice. E The frequency of electric discharge in the CNO group was reduced compared with the baseline value. Compared with the CNO group, the firing frequency of WDR neurons in the CNO + Yohimbine group was increased. Compared with the CNO + Yohimbine group, the firing frequency of WDR neurons in the wash-out group was lower. F In LC:SC activated mice, there was a significant attenuation of the response to 1 g von Frey induced by yohimbine, which indicated a spinal α2-adrenoceptor mechanism. G The firing frequency in the CNO group was decreased compared with the baseline, whereas it was lower in the wash-out group than that in the CNO + Yohimbine group. Data are expressed as mean + SEM, n = 6 mice. *p < 0.05, **p < 0.01, ns not statistically significant