Cannabigerol Attenuates Memory Impairments, Neurodegeneration, and Neuroinflammation Caused by Transient Global Cerebral Ischemia in Mice

Abstract

Evidence supporting the clinical use of neuroprotective drugs for cerebral ischemia remains limited. Spatial and temporal disorientation, along with cognitive dysfunction, are among the most prominent long-term consequences of hippocampal neurodegeneration following cerebral ischemia. Cannabigerol (CBG), a non-psychotomimetic constituent of Cannabis sativa, has demonstrated neuroprotective effects in experimental models of cerebral injury. This study investigated the neuroprotective mechanisms of CBG in mitigating memory impairments caused by transient global cerebral ischemia in C57BL/6 mice using the bilateral common carotid artery occlusion (BCCAO) model. Mice underwent sham or BCCAO surgeries and received intraperitoneal (i.p.) injections of either a vehicle or CBG (1, 5, or 10 mg/Kg), starting 1 h post-surgery and continuing daily for 7 days. Spatial memory performance and depression-like behaviors were assessed using the object location test (OLT) and tail suspension test (TST), respectively. Additional analyses examined neuronal degeneration, neuroinflammation, and neuronal plasticity markers in the hippocampus. CBG attenuated ischemia-induced memory deficits, reduced neuronal loss in the hippocampus, and enhanced neuronal plasticity. These findings suggest that CBG's neuroprotective effects against BCCAO-induced memory impairments may be mediated by reductions in neuroinflammation and modifications in neuroplasticity within the hippocampus.

Keywords: bilateral common carotid artery occlusion; cannabigerol; cognition; glial response; neuroprotection.

Figure 3

CBG reduces BCCAO-induced neuroinflammation in the hippocampus. (a–c) Representative photomicrographs of Iba-1-immunoreactive (Iba-1-IR), GFAP-immunoreactive (GFAP-IR), and NG2-immunoreative (NG2-IR) cells in the CA1 and CA3 subfields of the hippocampus. The dashed lines delimit the layers of neuronal bodies. (d,e) IOD of the microglia (Iba-1-IR) in the CA1 and CA3 subfields of the hippocampus. (f,g) IOD of the astrocytes (GFAP-IR) in the CA1 and CA3 subfields of the hippocampus. (h,i) IOD of the glial cell precursor (NG2-IR) in the CA1 and CA3 subfields of the hippocampus. The bars represent the mean ± SEM in the different groups (n = 5–6/group). * p < 0.05, ** p < 0.01, *** p < 0.001 for sham vs. BCCAO; # p < 0.05, ## p < 0.01, ### p < 0.001 BCCAO vs. BCCAO + CBG (one-way ANOVA followed by Sidak’s test).

Figure 4

The impact of CBG on ischemia-induced neuroplasticity in the hippocampus. (a) Representative photomicrographs of DCX-immunoreactive (DCX-IR) neurons in the GCL and SGZ of the hippocampal dentate gyrus. (b) Number of DCX-IR neurons in the SGZ and GCL of the dentate gyrus. (c) Representative Western blot bands of BDNF, proBDNF, and β-actin. (d,e) BDNF and proBDNF protein levels in the hippocampus. (f) Ratio between BDNF and proBDNF levels. The bars represent the mean ± SEM in the different groups (n = 5–7/group). ** p < 0.01, *** p < 0.001 for sham vs. BCCAO; # p < 0.05, ## p < 0.01, ### p < 0.001 for BCCAO vs. BCCAO + CBG (one-way ANOVA followed by Sidak’s test).

Figure 1

CBG improves memory impairment induced by BCCAO in mice. (a) Spatial learning and memory performance was analyzed in the OLT using the D2 exploration index at 1, 4, and 24 h intervals. (b) Depression-like behavior was evaluated in the TST by measuring the latency for the first episode of immobility (latency) and the immobility time. The bars represent the mean ± SEM in the different groups (n = 11–17/group). * p < 0.05 for sham vs. BCCAO; # p < 0.05 for BCCAO vs. BCCAO + CBG (one-way ANOVA followed by Sidak’s test).

Figure 2

CBG decreases hippocampal neurodegeneration induced by BCCAO. (a) Representative photomicrographs of the NeuN-immunoreactive (NeuN-IR) neurons in the CA1 and CA3 hippocampal subfields, indicating intact-appearing neurons (arrows). (b) Representative photomicrographs of the MAP-2-immunoreactive (MAP-2-IR) cells in the stratum radiatum (CA1 subfield) and stratum lucidem (CA3 subfield). The dashed lines delimit the layers of neuronal bodies. (c,d) Integrated optical density (IOD) of the NeuN-IR neurons in the CA1 and CA3 subfields of the hippocampus. (e,f) IOD of the MAP-2-IR in the CA1/stratum radiatum and CA3/stratum lucidem. The bars represent the mean ± SEM in the different groups (n = 5–6/group). *** p < 0.001 for sham vs. BCCAO; # p < 0.05, ## p < 0.01 for BCCAO vs. BCCAO + CBG (one-way ANOVA followed by Sidak’s test).

Figure 5

Experimental design. From day −7 to day −1 the animals were familiarized with the OLT environment. On day 1, sham or BCCAO surgery was performed, and Veh, CBG1, CBG5, or CBG10 was administered i.p. for 7 days. Behavioral testing was performed from day 9 to day 14 after BCCAO. Immediately after the last behavioral test, the animals were euthanized, and their brains were processed for immunohistochemical (IHC) and Western blot (WB) analysis. OLT, object location test; TST, tail suspension test.