[Anxiety-like behaviors induced by chronic administration of the synthetic cannabinoid 4F-ABUTINACA in rats and the underlying mechanisms].

Objectives

To elucidate the Δ⁹-tetrahydrocannabinol (THC)-like discriminative stimulus effects of 4F-ABUTINACA and to investigate the potential mechanisms underlying anxiety-like behaviors induced by chronic 4F-ABUTINACA administration.

Methods

A THC drug discrimination procedure was used in adult male rats to evaluate the THC-like discriminative stimulus effects of 4F-ABUTINACA and the effects of the cannabinoid receptor type 1 (CB1) antagonist rimonabant on these effects. In a separate cohort, rats received intraperitoneal injections of 4F-ABUTINACA at a high dose (2 mg/kg) or a low dose (0.3 mg/kg) for 15 consecutive days. Anxiety-like behaviors were assessed using the open field test and elevated plus maze at 1 day (short-term withdrawal) and 20 days (long-term withdrawal) after the final administration. Immunofluorescence staining was used to examine glial cell activation and changes in inhibitory synaptic markers in the hippocampus. Western blotting was performed to detect the expression of synaptic plasticity-related proteins in the rat hippocampus.

Results

After stable THC (2 mg/kg) discrimination was established, 4F-ABUTINACA (2 mg/kg) produced full substitution for THC, and this discriminative stimulus effect was partially inhibited by rimonabant. In the low-dose 4F-ABUTINACA group, rats exhibited anxiety-like behavior in the open field test at short-term withdrawal, accompanied by increased hippocampal glial marker expression (P<0.05), decreased expression of N-methyl-D-aspartate receptor subunits 2A (NR2A) and 2B (NR2B) and synaptosome-associated protein 25 kDa (SNAP25) (all P<0.05), and increased expression of glutamate receptor, ionotropic, AMPA 1 (GluA1) (P<0.05). Decreased gephyrin expression was observed at both short-term and long-term withdrawal (all P<0.05), whereas decreased vesicular GABA transporter (VGAT) expression and increased GluA2 expression were observed at long-term withdrawal (P<0.05). In the high-dose 4F-ABUTINACA group, rats exhibited anxiety-like behaviors and increased hippocampal glial marker expression at both short-term and long-term withdrawal (P<0.05), along with decreased NR2A, NR2B, and gephyrin expression (all P<0.05). Additionally, GluA1 expression increased at short-term withdrawal (P<0.05), while VGAT expression in the DG and CA3 subregions and SNAP25 expression were decreased at long-term withdrawal (all P<0.05).

Conclusions

4F-ABUTINACA produces THC-like discriminative stimulus effects via CB1 receptor activation, suggesting that it has abuse liability. Chronic 4F-ABUTINACA administration induces anxiety-like behaviors in rats, and the underlying mechanism may involve sustained hippocampal glial activation and impaired synaptic plasticity.