The Effects Of Environment During Adolescence Of Rat On Methamphetamine Self-administration And The Expression Of D2

Objective: The abuse and dependence of methamphetamine(considered as a kind ofnew drug) is popular more and more. To establish the effects of environment duringadolescence on methamphetamine self-administration, cue-induced drug seeking and theexpression of D2, we used western-blotting and self-administration of methamphetaminein our study.Methods: All the animals were socially housed till postnatal Day (PND)20. InExperiment1, rats (EE40-A or IE40-A) were reared in either socially enriched (EE) orsocially isolated environments (IE) from PND21to60. In Experimental2, rats werereared in the following condition from postnatal Day21to Day60. Group EE40-B andIE40-B were handled in the same fashion as group EE40-A and IE40-A in Experiment1.Group IE20+EE20and Group IE30+EE10were housed in IE during the first20or30daysand, then housed under EE for the remaining20or10days respectively. Locomotoractivity and Morris Water Maze were tested The effects of rearing conditions on theacquisition, maintenance, extinction, and reinstatement of methamphetamine (METH)self-administration were investigated. In Experiment1, the expression of D2wasexamined following Locomotor activity and Morris Water Maze test.Results:1. The effects on behavioral tasks in adult rats by environmental manipulation duringearly life.The present study demonstrated that IE animals exhibited higher level of locomotionthan EE animals, but EE animals showed enhanced performance during the Morris watermaze task.2. The effects on the expression of D2in adult rats’ brain by environmentalmanipulation during early life. The expression of D2in the nucleus accumbens has no significance diffrencesbetween IE and EE rats.3. The effects on the self-administration of methamphetamine in adult rats byenvironmental manipulation during early life.IE40and IE20+EE20animals were more readily acquired METH self-administrationthan EE40and IE30+EE10respectively. However, the effect of rearing conditions on themaintenance of METH self-administration was only seen at the lowest dose tested underFR schedule and breakpoints obtained from PR schedule were not significantly affected.EE40and IE20+EE20animals produced significantly fewer responses during theextinction and cue-induced reinstatement of METH self-administration, compared with IEand IE30+EE10ones respectively.Conclusion: Rearing condition plays a significant role in locomotor activity andspatial memory and behavioral effects of METH. The neurobiological mechanisms are stillunknown.