Optogenetic stimulation of dynorphinergic neurons within the dorsal raphe activate kappa opioid receptors in the ventral tegmental area and ablation of dorsal raphe prodynorphin or kappa receptors in dopamine neurons blocks stress potentiation of cocaine reward

•Kappa opioid activation in dopamine neurons enhances cocaine reward after stress.•Stress initially inhibits and then excites dopamine neurons through kappa opioid activation.•Inhibition of VTA dopamine neurons can initially suppress then enhance cocaine reward.•Projections from DRN neurons release dynorphins in the VTA to regulate excitability.