Chronic administration of methamphetamine increases the mRNA expression of diazepam binding inhibitor in rat brain

Anxiety is one of the common features of withdrawal syndrome caused by abuse-inducing drugs such as methamphetamine (MAP). The neural pathways associated with anxiety are established within the network sustained by diencephalon, cerebral cortex, cerebellum and hippocampus. Diazepam binding inhibitor (DBI), a peptide consisting of 87 amino acids, serves as an inverse agonist for the type A receptor of the gamma-aminobutyric acid (GABAA receptor) with endogenous anxiogenic potential. We examined the effect of chronic administration of MAP on the mRNA expression of DBI and DBI-related proteins, such as alpha 2 subunit of GABAA receptor (GABA-α2), peripheral-type benzodiazepine receptor (PBR), and pituitary adenylate cyclase-activating polypeptide (PACAP) in seven regions (diencephalon, cerebral cortex, cerebellum, striatum, hippocampus, midbrain, and pons-medulla) of the rat brain. The mRNA expression of DBI increased significantly in all areas of the brain, especially diencephalon, after chronic administration of MAP. The mRNA expression of PBR, GABA-α2 and PACAP increased significantly in all areas of the brain, especially cerebral cortex, after chronic administration of MAP. These results suggest that anxiety is associated with the mRNA expression of DBI as well as DBI-related genes.