OBJECTIVE Dopamine(DA)plays important roles in Pavlovian conditioning by mediating reward,learning and motivation.While the conditioning stimulation(CS) is the most important inducement for reinstatement in addiction....OBJECTIVE Dopamine(DA)plays important roles in Pavlovian conditioning by mediating reward,learning and motivation.While the conditioning stimulation(CS) is the most important inducement for reinstatement in addiction.The present study investigated the specific role of the DA projections to nucleus accumbens(NAc) and medial prefrontal cortices(mPFC) from ventral tegmental area(VTA) in reinstatement induced by cue.METHODS(1)Optogenetic intracranial self-stimulation and reinstatement.DAT-Cre transgenic mice received an injection of adeno-associated viral vectors encoding channelrhodopsin2(ChR2) or control vector into the VTA resulting in the selective expression of these opsins in DA neurons.Then,we stimulated the VTA,NAc(core and shel) or mP FC [prelimbic cortex(PL) and infralimbic cortex(IL)] via an optical fiber.In the reinforcement test,the mice with ChR2 learned instrumental responses corresponding to the delivery of photostimulation into the VTA with multiple frequencies and during time;in the reinstatement phase,stimulation of the DA projections to NAc(core or shell) or mPFC(IL and PL) from VTA to induce reinstatement after 2 weeks of extinction of self-stimulation.(2)Reinstatement in cocaine self-administration.Virus encoding ChR2 or hM4 Di were injected into VTA of DAT-Cre transgenic mice.The mice with ChR2 and hM4 Di in DA neurons were trained to establish self-administration of cocaine.After 2 weeks of extinction,laser stimulation of the DA projections to NAc(core or shel) or mP FC(IL and PL) was conducted to induce reinstatement.After that,Clozapine was injected in NAc core to test the impacts of VTA-NAc core depression on the reinstatement induced by cue.(3) Photometry of VTA DA neurons in reinstatement.DAT-Cre transgenic mice were received an injection of AAV-DIO-Gcamp6 m into VTA.After cocaine self-administration and extinction,mice with Gcamp6 m were challenged by cue(paired with cocaine previously) and the photometry of VTA DA neurons was conducted during the reinstatement.RESULTS(1)The enhanced self-stimulation behavior was positive correlation with the stimulation of DA neurons in VTA according to the increasing frequency of stimulation and extent stimulation duration time.Furthermore,DA receptor antagonists significantly depressed the frequency curve.(2) Only stimulation of the projections to the NAc core from the VTA significantly induced reinstatement after extinction of self-stimulation,neither shell nor mPFC(PL or IL).(3) Depression of VTA-NAc core projection significantly inhibited the reinstatement induced by cue.(4) DA neurons in VTA were activated when the cue appeared during the period of reinstatement test.CONCLUSION Mesocorticolimbic DA system directly modulate the reinforcement dependant on DA receptor.The activity of DA neurons in VTA is necessary for cue induced relapse.Importantly,projections to NAc core from VTA perform the unique effects in reinstatement.展开更多
基金National Key Research and Development (2016YFC0800907)Project 973 (2015CB553504)+1 种基金National Natural Science Foundation of China(81573405)Beijing Nova Program(xx2014A014).
文摘OBJECTIVE Dopamine(DA)plays important roles in Pavlovian conditioning by mediating reward,learning and motivation.While the conditioning stimulation(CS) is the most important inducement for reinstatement in addiction.The present study investigated the specific role of the DA projections to nucleus accumbens(NAc) and medial prefrontal cortices(mPFC) from ventral tegmental area(VTA) in reinstatement induced by cue.METHODS(1)Optogenetic intracranial self-stimulation and reinstatement.DAT-Cre transgenic mice received an injection of adeno-associated viral vectors encoding channelrhodopsin2(ChR2) or control vector into the VTA resulting in the selective expression of these opsins in DA neurons.Then,we stimulated the VTA,NAc(core and shel) or mP FC [prelimbic cortex(PL) and infralimbic cortex(IL)] via an optical fiber.In the reinforcement test,the mice with ChR2 learned instrumental responses corresponding to the delivery of photostimulation into the VTA with multiple frequencies and during time;in the reinstatement phase,stimulation of the DA projections to NAc(core or shell) or mPFC(IL and PL) from VTA to induce reinstatement after 2 weeks of extinction of self-stimulation.(2)Reinstatement in cocaine self-administration.Virus encoding ChR2 or hM4 Di were injected into VTA of DAT-Cre transgenic mice.The mice with ChR2 and hM4 Di in DA neurons were trained to establish self-administration of cocaine.After 2 weeks of extinction,laser stimulation of the DA projections to NAc(core or shel) or mP FC(IL and PL) was conducted to induce reinstatement.After that,Clozapine was injected in NAc core to test the impacts of VTA-NAc core depression on the reinstatement induced by cue.(3) Photometry of VTA DA neurons in reinstatement.DAT-Cre transgenic mice were received an injection of AAV-DIO-Gcamp6 m into VTA.After cocaine self-administration and extinction,mice with Gcamp6 m were challenged by cue(paired with cocaine previously) and the photometry of VTA DA neurons was conducted during the reinstatement.RESULTS(1)The enhanced self-stimulation behavior was positive correlation with the stimulation of DA neurons in VTA according to the increasing frequency of stimulation and extent stimulation duration time.Furthermore,DA receptor antagonists significantly depressed the frequency curve.(2) Only stimulation of the projections to the NAc core from the VTA significantly induced reinstatement after extinction of self-stimulation,neither shell nor mPFC(PL or IL).(3) Depression of VTA-NAc core projection significantly inhibited the reinstatement induced by cue.(4) DA neurons in VTA were activated when the cue appeared during the period of reinstatement test.CONCLUSION Mesocorticolimbic DA system directly modulate the reinforcement dependant on DA receptor.The activity of DA neurons in VTA is necessary for cue induced relapse.Importantly,projections to NAc core from VTA perform the unique effects in reinstatement.
