Antidepressant dose of taurine increases mRNA expression of GABAA receptor α2 subunit and BDNF in the hippocampus of diabetic rats

Abstract

Diabetes mellitus is a metabolic disorder associated with higher risk for depression. Diabetic rats present depressive-like behaviors and taurine, one of the most abundant free amino acids in the brain, reverses this depressive behaviors. Because taurine is a GABAA agonist modulator, we hypothesize that its antidepressant effect results from the interaction on this system by changing α2 GABAA receptor subunit expression, beside changes on BDNF mRNA, and memory in diabetic rats. Streptozotocin-diabetic and non-diabetic Wistar rats were daily injected with 100mg/kg of taurine or saline, intraperitoneally, for 30 days. At the end of the experiment, rats were exposed to the novel object recognition memory. Later they were euthanized, the brains were weighed, and the hippocampus was dissected for α2 GABAA subunit and BDNF mRNA expression. Real-time quantitative PCR (qPCR) showed that diabetic rats presented lower α2 GABAA subunit and BDNF mRNA expression than non-diabetic rats and taurine increased both parameters in these sick rats. Taurine also reversed the lower brain weight and improved the short-term memory in diabetic rats. Thus, the taurine antidepressant effect may be explained by interference with the GABA system, in line to its neuroprotective effect showed here by preventing brain weight loss and improving memory in diabetic rats.