GABAergic VTA Mediates Predatory Hunting In Mice

Background:Predatory hunting is highly conserved during evolution,exerting an essential role in the survival and development of animals.Previous researches have revealed that electric stimulation of ventral tegmental area(VTA)elicited predatory attack,but the exact neural circuit of VTA underlying predatory hunting remains unknown.Neuronal anatomical evidences show that GABAergic VTA innervates many hunting-related and feeding-related brain regions.Besides,our previous research has shown that activation of GABAergic VTA provoked mice to fiercely bite the food,which resembles with predatory attack.These evidences suggest that GABAergic VTA may mediate predatory hunting.Objective:By using optogenetic technology,this study aims to evaluate the role of GABAergic VTA on predatory hunting,for further completing the comprehension of neural circuit underlying predatory hunting.Method:(1)A viral cocktail of AAV-VGAT-Cre and AAV-h EF1?-DIO-GCa MP6m was injected into the VTA of C57/BL6 mice by stereotaxic injection,and an optic fiber was implanted 0.3 mm above the VTA.Following expression for 4 weeks,fiber photometry system was used to monitor the activity of GABAergic VTA during predation for uncovering the correlation between predatory hunting and VTA GABAergic neurons.(2)A viral cocktail of AAV-VGAT-Cre and AAV-h EF1?-DIO-Ch R2-m Cherry was injected into the VTA of C57/BL6 mice by using stereotaxic injection,and an optic fiber was implanted 0.3 mm above the VTA.4 weeks later,a 473 nm blue light was delivered,and the effect of VTA GABA neurons on predatory hunting was tested by behavioral experiments,including cricket-hunting test,food-foraging test and object-exploration test.(3)After all behavior test were done,mice were treated with optogenetic illumination and were perfused.The brain were removed and sectioned.The immunofluorescence staining of c-Fos protein was performed,and the co-labeled percentage of c-Fos protein within VTA were analyzed.(4)Similarly,by using optogenetic technology,the effect of VTA GABAergic neurons projecting to lateral hypothalamus(LH)on predatory hunting was tested,for exploring the exact neural circuit underlying predatory hunting.Result:(1)Fiber photometry test showed that VTA GABAergic neurons were activated during predatory attack.(2)Photo-activation of VTA GABAergic neurons significantly decreased the latency of mice initiating attack on crickets(P<0.001),and increased the attack probability(P<0.001).The number of cricket casualties caused by Ch R2-expressing mice were increased during light-on sessions(P<0.001).In the food-foraging test,Photo-activation of VTA GABAergic neurons remarkably induced food-foraging behavior in mice.The latency of mice leaving the nest and entering the feeding area(P<0.001)were significantly decreased during light-on sessions.After entering the feeding area,mice immediately bit and carried the food.Thus,the time mice spending in the feeding area was increased(P<0.001).In the object-exploration test,photo-activation of VTA GABAergic neurons significantly provoked mice to explore different objects in the environment.Mice performed a series of hunting-like behavior toward the object,including pawing,biting and carrying,therefore,the distance of object dislocation was increased(P<0.05).(3)After treatment of optogenetic illumination,c-Fos protein were largely expressed within VTA,and approximately 56.3%of neurons expressing Ch R2-m Cherry co-localized with c-Fos~+cells.(4)Photo-activation of GABAergic VTA-LH neural pathway promoted predatory hunting in mice.The latency of mice attacking on crickets was reduced(P<0.001),the attack probability and the number of cricket casualties(P<0.001)were significantly increased.Photo-activation of GABAergic VTA-LH neural pathway induced food-foraging behavior in mice.The latency of mice leaving the nest and entering the feeding area were significantly decreased during light-on sessions(P<0.001).The time mice spending in the feeding area was increased(P<0.001).Photo-activation of GABAergic VTA-LH neural pathway significantly provoked mice to explore different objects in the environment,the distance of object dislocation was increased(P<0.05).Conclusion:1.GABAergic VTA induced predatory hunting behavior in mice.2.GABAergic VTA induced predatory hunting behavior through projection to LH.