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INTRODUCTIONAMPH and METH are known to increase DAergic signaling in the brain reward system by stimulating the release of DA through the reversal of DAT function. However, there is evidence that insulin signaling pathways have the ability to modulate DAT functions. Some studies have reported that hypoinsulinemia attenuates DAT functions, and as a consequence, psychostimulant-induced behaviors are reduced. In the present study, we examined the effects of acute food deprivation, which also reduces insulin levels, on METH-induced locomotor sensitization.METHODSSeparate groups of rats were treated with METH (1 mg/kg i.p.) or saline for 5 days (development phase). On the test day (expression phase), the groups were treated with METH or saline after food deprivation for 24 h. Furthermore, in separate groups of rats, levels of glucose, insulin, and phosphorylation of Akt at Ser473 were also examined after food deprivation for 24 h.RESULTSThe results showed that repeated administration of METH induced a progressive increase in locomotor activity in rats during the development phase. However, METH administration in the expression phase produced a decrease in locomotor activity after 24 h of food deprivation. In addition, the results showed that a reduction in glucose, insulin, and Akt levels occurred as a result of food deprivation.CONCLUSIONThese results are in line with previous studies and suggest that food deprivation reduces some behavioral effects of psychostimulants such as AMPH and METH.HighlightsAdministration of METH increases DAergic neurotransmission by interfering with proper DA transporter (DAT) functionSome evidence suggests that insulin signaling pathways modulate the DAT in the brain reward systemAcute food deprivation reduces glucose and insulin levelsThis study examined the effects of acute food deprivation on METH-induced locomotor sensitizationPresent study showed that food deprivation for 24 h reduced METH-induced locomotor sensitizationPlain Language SummaryThe dopamine transporter (DAT) is responsible for the reuptake of dopamine (DA) and the termination of DA neurotransmission. DAT is also the target for psychostimulant drugs such as cocaine, amphetamine, and methamphetamine. These drugs produce an increase of DA neurotransmission in the reward system. It is now well established that insulin levels modulate DAT function. Several studies have reported that hypoinsulinemia attenuates DAT function, and as a consequence, psychostimulant-induced behaviors are reduced. Food deprivation reduces glucose and insulin levels. In the present study we evaluated the effects of food deprivation on methamphetamine-induced locomotor sensitization. This behavior reflects brain neuroadaptations that contribute to drug addiction. Rats of the main experimental group were treated with methamphetamine for 5 days (development phase). On the test day (expression phase) the rats were treated with methamphetamine after food deprivation for 24 h. In separated groups of rats levels of glucose and insulin were evaluated after food deprivation for 24 h. The results showed that acute food deprivation reduced methamphetamine-induced locomotor sensitization. It was also observed that insulin and glucose levels were reduced after food deprivation. The results of the present study suggest that food deprivation can modulate some behavioral effects of methamphetamine. |
