Putative Antianxiety Property of Oral Enalapril Formulation in Mice: a Preclinical and in silico Study.

INTRODUCTION Anxiety disorders, characterized by overwhelming fear, affect more than 30% of the global population. Recent evidence indicates that antihypertensive medications could offer symptomatic relief for anxiety, supporting their potential for repurposing. The objective is to investigate the anxiolytic-like effects of an enalapril formulation.

METHODS 60 Swiss mice (30 ± 5 g, aged 6-8 weeks) were randomly assigned to groups and received oral treatments with either vehicle (10 mL/kg), diazepam (DZP, 5 mg/kg), reference enalapril (ENAR), enalapril formulation (ENAF), losartan (LOS), or propranolol (PRO), each at a dose of 10 mg/kg. After 60 minutes, the animals were exposed to 5 minutes of exploratory activity in the open field, elevated plus maze (EPM), light-dark box (LDB), and a minute of rotarod.

RESULTS One-way ANOVA demonstrated differences for the total crossing (p=0.0001), freezing time (p=0.0001), number of rearing (p=0.002), time spent (p=0.002), and crossing at the center (p=0.0001) of the open field. Unlike in the rotarod (p>0.05), the ENAR, ENAF, LOS, and PRO elicit increases (p<0.05) in the total number of arm entries and time spent on the open arms of EPM while increasing the number of transitions (p<0.05) and time spent in the light area of the LDB (p=0.001). In silico screening suggests stability of interaction with several amino acid residues overlapping with the flumazenil binding site, with the binding energy (ΔE) = -22.59kcal/mol towards the benzodiazepine binding site (flumazenil ΔE = -43.92kcal/mol).

DISCUSSION The repositioning of drugs available to the population is an interesting approach toward the discovery of alternative or add-on treatments for anxiety. Ongoing resort to repurposing, reusing, reprofiling, and rediscovery of "old" drugs for a new indication seems to be an interesting way out of failures, the expensive and slow pace of new drug discovery.

CONCLUSION Enalapril demonstrates anxiolytic-like properties, further insights into the GABAergicrenin- angiotensin-aldosterone mechanistic hypothesis.