@entity1068 drinking-in-the-dark facilitates behavioral sensitization to @entity1068 in C57BL/6J, BALB/cByJ, but not in mu-opioid receptor deficient CXBK XXXX .

@entity167 @entity19 @entity1068
BACKGROUND: Neuroplasticity associated with drug-induced behavioral sensitization has been associated with excessive drug pursuit and consumption characteristic of addiction. Repeated intraperitoneal (ip) injections of @entity1068 ( @entity167 ) can induce psychomotor sensitization in @entity19 . In terms of its clinical relevance, however, it is important to determine whether this phenomenon can also be produced by voluntary @entity167 consumption. METHODS: The present investigation used a drinking-in-the-dark (DID) methodology to induce high levels of @entity167 drinking in @entity19 ; @entity167 replaces water for 2 or 4h, starting 3h after the beginning of the dark cycle. Animals followed a 3-week DID protocol prior to an evaluation of @entity167 -induced locomotor activity (acute and repeated @entity167 ). For the first week, animals had access to 20% @entity167 . On weeks 2 and 3, different concentrations of @entity167 (10, 20 or 30%) were used. Three different inbred strains of @entity19 were used: C57BL/6J (B6), BALB/cByJ (BALB), and CXBK. The CXBK @entity19 line was used because of its reduced expression and functioning of brain mu-opioid receptors, which have been suggested to participate in the development of @entity167 -induced sensitization. B6 and BALB @entity19 were used as controls. RESULTS: B6 and CXBK @entity19 presented comparable levels of @entity167 drinking (approx. 3g/kg in 2h), that were higher than those showed by BALB. All animals, regardless of genotype, adjusted volume of @entity167 intake to obtain stable g/kg of @entity167 across concentrations. Previous @entity167 DID produced (B6) or potentiated (BALB) sensitization to @entity167 ; this effect was not seen in CXBK. Western blot analysis showed a reduced number of mu-opioid receptors in several brain regions of CXBK as compared to that of B6 and BALB @entity19 . CONCLUSIONS: In summary, here we show that the DID methodology can be used to trigger @entity167 -induced neuroplasticity supporting psychomotor sensitization, a process that might require participation of mu-opioid receptors.
