17β-Trenbolone modulates anxiety-related synaptic plasticity by affecting the interaction between hippocampal TACR3 and systemic testosterone in male mice

Anxiety Disorder is a common neurological disorder for which ubiquitous environmental endocrine disruptors may be risk factors. 17β-trenbolone (17-TB) has been recognized as a potential environmental endocrine disruptor and its neurotoxic effects have attracted attention. Tachykinin receptor 3 (TACR3), a G protein-coupled receptor involved in pubertal anxiety, and its underlying neural mechanisms remain enigmatic. Therefore, this study investigated the possible relationship between 17-TB and TACR3, testosterone (T), and synaptic plasticity. Our results showed that adolescent male Balb/c mice developed significant anxiety-like behavior after four weeks of exposure to environmentally relevant concentrations of 17-TB (100 μg/kg/day). Transcriptomic RNA-Seq results showed that 17-TB affected abnormal synaptic transmission signals in the hippocampus. Electrophysiological results showed that 17-TB reduced the activity of hippocampal dentate gyrus (DG) neurons and led to the downregulation of hippocampal TACR3 and T levels. In addition, Western blot, immunohistochemistry, ELISA, and qRT-PCR showed that 17-TB exposure led to the downregulation of key hippocampal synaptic proteins PSD95, Gephyrin, and Syn, and induced a metabolic imbalance in glutamate (Glu)/GABA signaling, affecting dopamine signaling. Interestingly, testosterone supplementation (10 mg/kg/day) was effective in ameliorating the above phenomena and alleviating anxiety-like behaviors. These results suggest that 17-TB modulates anxiety-related synaptic plasticity by regulating hippocampal TACR3 and T interactions in vivo. In conclusion, our study contributes to understanding the neurobehavioral and potential mechanistic effects of environmental 17-TB exposure in mammals. It alerts the public to the health risks of chemicals to mammals and suggests new research directions and potential therapeutic targets.