Synaptic correlates of benzodiazepine tolerance.

Benzodiazepines are among the most widely prescribed psychotropic agents, exhibiting anxiolytic, hypnotic, anticonvulsant, and myorelaxant properties primarily mediated through positive allosteric modulation of type A γ-aminobutyric acid receptors (GABAARs)-the principal inhibitory receptors in the mammalian brain. However, prolonged benzodiazepine administration frequently results in the development of tolerance, a phenomenon characterized by reduced pharmacological efficacy and the need for escalating doses to sustain therapeutic benefit. Accumulating evidence indicates that benzodiazepine tolerance arises from complex neuroadaptive processes that induce long-lasting reorganization of neural circuits regulating stress responsiveness, arousal, and reward processing. In this review, we synthesize current knowledge on the clinical and societal impact of benzodiazepine use, delineate the molecular targets and mechanisms underlying their psychotropic effects on brain physiology and behaviour, and provide a comprehensive overview of the molecular and cellular adaptations contributing to benzodiazepine tolerance and withdrawal. Particular emphasis is placed on how prolonged exposure remodels inhibitory and excitatory synaptic organization. Furthermore, we examine evidence for benzodiazepine-induced synaptic adaptations in patients and highlight the potential of integrative in vivo imaging approaches to elucidate these processes within the complexity of the human brain. Finally, we propose that advancing these research avenues could foster a paradigm shift in the clinical use of benzodiazepines and guide the development of next-generation therapeutics with improved safety and efficacy profiles.