DIAZEPAM-INDUCED TRANSCRIPTIONAL REGULATION OF GABAA RECEPTOR α1 SUBUNIT GENE VIA L-TYPE VOLTAGE-GATED CALCIUM CHANNEL ACTIVATION IN RAT CEREBROCORTICAL NEURONS

MEDINA, NELSY BEATRIZ; FOITZICK, MARÍA FLORENCIA; IGLESIAS GARCÍA, LUCÍA CANDELA; GRAVIELLE, MARÍA CLARA

Mar del Plata

Congreso; LI Reunión Anual de la Asociación Argentina de Farmacología Experimental; 2020

Asociación Argentina de Farmacología Experimental

GABA-A receptorsare targets of different pharmacologically relevant drugs, such asbarbiturates, benzodiazepines, and anesthetics. In particular, benzodiazepinesare prescribed for the treatment of anxiety, sleep disorders, and seizuredisorders. Prolonged activation of GABA-A receptors by endogenous and exogenousmodulators induces adaptive changes that lead to tolerance. For example,chronic administration of benzodiazepines produces tolerance to most of theirpharmacological actions, limiting their usefulness. The mechanism of toleranceis still unknown. We havepreviously demonstrated that chronic diazepam administration in rats results intolerance to the sedative and anxiolytic effects which is accompanied with adecrease in the interactions between GABA and benzodizepine binding sites(uncoupling) in cerebral cortex. The aim of this work was to investigate themolecular mechanism of benzodiazepine tolerance in an in vitro model of primary neuronal cultures from rat cerebralcortex. The exposure of cultured neurons to diazepam for 48 h produced a 40 %uncoupling (p<0.05) which was prevented in the presence of nifedipine, aninhibitor of L-type voltage-gated calcium channels (L-VGCCs). Benzodiazepinetreatment also induced a 45 % decrease (p<0.05) in GABA-A receptor alpha1subunit mRNA levels (p<0.05) that was inhibited by nifedipine. Wehypothesized that the adaptive changes of GABA-A receptors induced by sustainedexposure to benzodiazepine are mediated by a signaling pathway that involvesactivation of L-VGCCs. Results from calcium mobilization and nuclear run-onassays suggested that benzodiazepine exposure produces an increase in thecalcium influx through L-VGCCs that activates an intracellular signalingcascade finally leading to the transcriptional repression of alpha1 subunitgene expression. Insights into the mechanism of benzodiazepine tolerance willcontribute to the design of new drugs that can maintain their efficacies afterlong term treatments.