(A) Diagram of surgical procedures and recording task. Retrograde Cre-dependent HSV-LS1L-GCaMP6s viral vector was injected into the VTA of vglut2:cre or vgat:cre mice and the retrograde AAV6-Syn-ChR2-eYFP viral vector was injected into the sciatic nerve. An optic fiber was implanted over the LPO for fiber photometry calcium imaging recordings of LPO-VGluT2 or LPO-VGaT neurons innervating the VTA in response to a pain conditioning task, where a 5 s tone predicted 10 s of nociceptive induced by intra-sciatic stimulation through an LED floor.
(B) LPO-VGluT2 neurons innervating the VTA signal both a cue predicting the onset of stimulation and the delivery of nociceptive stimulation (generalized linear model; n = 8; session × epoch interaction, χ2(6) = 33.58, p < 0.0001; *p < 0.05, **p < 0.01, ***p < 0.001; #p = 0.063; data represent the mean ± SEM).
(C) LPO-VGaT neurons innervating the VTA signal predictable nociceptive stimulation (generalized linear model; n = 8; main effect of epoch [inset], χ2(2) = 7.58, p = 0.023; *p < 0.05; data represent the mean ± SEM). (See also Figures S2 and S3.)