Blockade of NOP receptor modulates anxiety-related behaviors in mice exposed to inescapable stress.

Aldemara I Silva, Victor A D Holanda, Joaquim G Azevedo Neto, Edilson D Silva Junior, Vanessa P Soares-Rachetti, Girolamo Calo, Chiara Ruzza, Elaine C Gavioli

Psychopharmacology 2020 Jun

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Depression and anxiety frequently co-occur, and this has important clinical implications. Previous studies showed that activation of the nociceptin/orphanin FQ receptor (NOP) elicits anxiolytic effects, while its blockade promotes consistent antidepressant actions. NOP antagonists are effective in reversing footshock-induced depressive-like behaviors, but their effects on stress-induced anxiety are still unclear. This study aimed to investigate the effects of the NOP antagonist SB-612111 on footshock stress-induced anxiety behaviors. Male Swiss mice were exposed to inescapable electric footshock stress, and behavioral phenotype was screened based on the ability to escape from footshock (i.e., helpless or non-helpless). Animals were then treated with diazepam (1 mg/kg) and SB-612111 (0.1-10 mg/kg), and their behavior was assessed in the elevated plus-maze (EPM) and open field test. When compared with non-stressed mice, helpless, but not non-helpless, animals displayed significant reductions in the time spent in and entries into open arms in the EPM. Diazepam significantly increased open arms exploration in helpless, non-helpless, and non-stressed mice. However, treatment with the NOP antagonist SB-612111 was inactive in naive mice, while it reversed anxiogenic-related behaviors in helpless mice and increased anxiety states in non-helpless mice. No effects on locomotion were observed. Helpless mice displayed increased anxiety compared to non-stressed and non-helpless animals, thus supporting use of this approach as an animal model to investigate anxiety/depression comorbidity. Additionally, SB-612111 modulated anxiety-like behaviors in male mice depending on individual stress susceptibility. Ultimately, NOP antagonists could be useful for treating anxiety in depressed patients.

Citation

Aldemara I Silva, Victor A D Holanda, Joaquim G Azevedo Neto, Edilson D Silva Junior, Vanessa P Soares-Rachetti, Girolamo Calo, Chiara Ruzza, Elaine C Gavioli. Blockade of NOP receptor modulates anxiety-related behaviors in mice exposed to inescapable stress. Psychopharmacology. 2020 Jun;237(6):1633-1642