Cannabinoid Receptor 2 Blockade Prevents Anti-Depressive-like Effect of Cannabidiol Acid Methyl Ester in Female WKY Rats

Abstract

The pathophysiology of major depressive disorder (MDD) is diverse and multi-factorial, yet treatment strategies remain limited. While women are twice as likely to develop the disorder as men, many animal model studies of antidepressant response rely solely on male subjects. The endocannabinoid system has been linked to depression in clinical and pre-clinical studies. Cannabidiolic Acid-Methyl Ester (CBDA-ME, EPM-301) demonstrated anti-depressive-like effects in male rats. Here, we explored acute effects of CBDA-ME and some possible mediating mechanisms, using a depressive-like genetic animal model, the Wistar-Kyoto (WKY) rat. In Experiment 1, Female WKY rats underwent the Forced swim test (FST) following acute CBDA-ME oral ingestion (1/5/10 mg/kg). In Experiment 2, Male and female WKY rats underwent the FST after injection of CB1 (AM-251) and CB2 (AM-630) receptor antagonists 30 min before acute CBDA-ME ingestion (1 mg/kg, males; 5 mg/kg, females). Serum levels of Brain-Derived Neurotrophic Factor (BDNF), numerous endocannabinoids and hippocampal Fatty Acid Amide Hydrolase (FAAH) levels were assessed. Results indicate that females required higher doses of CBDA-ME (5 and 10 mg/kg) to induce an anti-depressive-like effect in the FST. AM-630 blocked the antidepressant-like effect in females, but not in males. The effect of CBDA-ME in females was accompanied by elevated serum BDNF and some endocannabinoids and low hippocampal expression of FAAH. This study shows a sexually diverse behavioral anti-depressive response to CBDA-ME and possible underlying mechanisms in females, supporting its potential use for treating MDD and related disorders.

Keywords: Forced swim test (FST); Wistar–Kyoto (WKY); cannabidiolic acid methyl ester; endocannabinoid system; genetic animal models of depression; major depression disorder.

Figure 1

Conversion of cannabigerolic acid (CBGA), to cannabidiolic acid (CBDA), to cannabidiol (CBD) and CBDA stable analogue CBDA methyl ester (CBDA-ME) (ChemDraw Professional drawing).

Figure 2

Schematic drawing of the rat hippocampus area that was taken—CA1, CA3 and the dentate gyrus (DG). Figure was taken from: http://labs.gaidi.ca/rat-brain-atlas/?ml=-2.5&ap=-3.8&dv=1.6, accessed on 15 July 2022.

Figure 3

(A) Graphic description of the experimental procedure—Experiment 1. (B) Graphic description of the experimental procedure—Experiment 2.

Figure 4

(A) Duration of immobility (mean + SEM) of female WKY rats (B) Duration of swimming (mean + SEM) of female WKY rats. Rats ingested either vehicle (n = 13) or 1 mg/kg CBDA-ME (n = 12), 5 mg/kg CBDA-ME (n = 12), 10 mg/kg CBDA-ME (n = 12). ** p < 0.01, * p < 0.05.

Figure 5

(A) Duration of immobility of female WKY rats (B) duration of swimming (mean + SEM) of female WKY rats. Rats received either vehicle (n = 13) or 5 mg/kg CBDA-ME (n = 13), 1 mg/kg AM251 + 5 mg/kg CBDA-ME (n = 12), 1 mg/kg AM630 + 5 mg/kg CBDA-ME (n = 12), 30 mg/kg Imipramine (n = 12). * p < 0.05.

Figure 6

BDNF blood level (mean + SEM) of female WKY rats. Rats received either vehicle (n = 7) or 5 mg/kg CBDA-ME (n = 7), 1 mg/kg AM251 + 5 mg/kg CBDA-ME (n = 7), 1 mg/kg AM630 + 5 mg/kg CBDA-ME (n = 7). * p < 0.05.

Figure 7

Selected endocannabinoids blood level (mean + SEM) of female WKY rats. Rats received either vehicle (n = 4) or 5 mg/kg CBDA-ME (n = 5), 1 mg/kg AM251 + 5 mg/kg CBDA-ME (n = 5), 1 mg/kg AM630 + 5 mg/kg CBDA-ME (n = 5). * p < 0.05; ** p< 0.01.

Figure 8

FAAH expression in the hippocampus (mean + SEM) of female WKY rats. Rats received either vehicle (n = 4) or 5 mg/kg CBDA-ME (n = 5), 1 mg/kg AM251 + 5 mg/kg CBDA-ME (n = 5), 1 mg/kg AM630 + 5 mg/kg CBDA-ME (n = 5). * p < 0.05, ** p< 0.01.