An anxiogenic drug, FG 7142, induced an increase in mRNA of Btg2 and Adamts1 in the hippocampus of adult mice

BACKGROUND: Anxiety and stress-related disorders are among the most common psychiatric disorders. The hippocampus is a crucial brain area involved in the neural circuits of the pathophysiology of anxiety and stress-related disorders, and GABA is one of most important neurotransmitters related to these disorders. An anxiogenic drug and a pharmacological stressor, FG7142 (N-methyl-ß-carboline-3-carboxamide), produces anxiety in humans and experimental animals, acting at the benzodiazepine sites of the GABA(A) receptors as a partial inverse agonist. This drug as well as immobilization stress produced an increased mRNA in a number of genes, e.g., Btg2 and Adamsts1, in the cortex of rodents. The present study was carried out to clarify the effect of the anxiogenic drug on the gene expressions in the hippocampus and to obtain a new insight into the GABAergic system involved in the pathophysiology of the disorders. METHOD: We examined the effects of FG7142 on the gene expression of Btg2 and Adamts1 in the hippocampus of mice using a quantitative RT-PCR method as well as an in situ hybridization method. RESULTS: The intraperitoneal administration of FG7142 at a dose of 20 mg/kg, but not 10 mg/kg, induced a statistically significant increase in the hippocampal mRNA of both genes in adult mice (postnatal days 56), being blocked by co-administrations of flumazenil (twice of 10 mg/kg, i.p.), an antagonist at the benzodiazepine binding site, while FG7142 failed to produce any change in the gene expressions in infant mice (postnatal days 8). In addition, the in situ hybridization experiment demonstrated an upregulation of the gene expressions restricted to the dentate gyrus of the hippocampus in adult mice. CONCLUSIONS: The present study suggests a functional coupling between the GABAergic system and the transcriptional regulation of the two genes (Btg2 and Adamsts1) in the hippocampus of adult mice, which may play a role in the brain function related to anxiety and stress such as memory of fear.