Cannabidiol, a non-psychotropic component of cannabis, attenuates vomiting and nausea-like behaviour via indirect agonism of 5-HT(1A) somatodendritic autoreceptors in the dorsal raphe nucleus

Abstract

Background and purpose: To evaluate the hypothesis that activation of somatodendritic 5-HT(1A) autoreceptors in the dorsal raphe nucleus (DRN) produces the anti-emetic/anti-nausea effects of cannabidiol (CBD), a primary non-psychoactive cannabinoid found in cannabis.

Experimental approach: The potential of systemic and intra-DRN administration of 5-HT(1A) receptor antagonists, WAY100135 or WAY100635, to prevent the anti-emetic effect of CBD in shrews (Suncus murinus) and the anti-nausea-like effects of CBD (conditioned gaping) in rats were evaluated. Also, the ability of intra-DRN administration of CBD to produce anti-nausea-like effects (and reversal by systemic WAY100635) was assessed. In vitro studies evaluated the potential of CBD to directly target 5-HT(1A) receptors and to modify the ability of the 5-HT(1A) agonist, 8-OH-DPAT, to stimulate [(35) S]GTPγS binding in rat brainstem membranes.

Key results: CBD suppressed nicotine-, lithium chloride (LiCl)- and cisplatin (20 mg·kg(-1) , but not 40 mg·kg(-1) )-induced vomiting in the S. murinus and LiCl-induced conditioned gaping in rats. Anti-emetic and anti-nausea-like effects of CBD were suppressed by WAY100135 and the latter by WAY100635. When administered to the DRN: (i) WAY100635 reversed anti-nausea-like effects of systemic CBD, and (ii) CBD suppressed nausea-like effects, an effect that was reversed by systemic WAY100635. CBD also displayed significant potency (in a bell-shaped dose-response curve) at enhancing the ability of 8-OH-DPAT to stimulate [(35) S]GTPγS binding to rat brainstem membranes in vitro. Systemically administered CBD and 8-OH-DPAT synergistically suppressed LiCl-induced conditioned gaping.

Conclusions and implications: These results suggest that CBD produced its anti-emetic/anti-nausea effects by indirect activation of the somatodendritic 5-HT(1A) autoreceptors in the DRN.

Linked articles: This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.

Figure 1

Mean (±SEM) number of vomiting episodes elicited by nicotine (5 mg·kg⁻¹, s.c.) and LiCl (390 mg·kg⁻¹, i.p.), among shrews pretreated with saline (SAL) or WAY100135 (10 mg·kg⁻¹, i.p.) and vehicle (VEH) or CBD (5 mg·kg⁻¹, sc). *P < 0.05, significantly different from all other groups.. The number of shrews in each condition is indicated in parentheses below pretreatment group name. The male (M) to female (F) (M : F) ratio within each treatment group for nicotine treated groups is saline-vehicle (7:5), saline-CBD (6:4), WAY-vehicle (4:4), WAY-CBD (6:4) and shrew age at the time of experimentation ranged from 44 days to 178 days with a mean of 96 days. The M : F ratio within each treatment group for LiCl treated groups is: saline-vehicle (6:8), saline-CBD (8:8), WAY-vehicle (4:4) and WAY-CBD (8:8).

Figure 2

Mean (±SEM) number of vomiting episodes elicited by 20 mg·kg⁻¹ cisplatin (Panel A) or 40 mg·kg⁻¹ cisplatin (Panel B) by shrews pretreated with saline (SAL; right-hand sections) or WAY100135 (10 mg·kg⁻¹, i.p.; left-hand sections) prior to the second pretreatment of vehicle (VEH), 5 mg·kg⁻¹ CBD or 10 mg·kg⁻¹ CBD. *P < 0.05, significant difference between other groups. The number of shrews in each group is indicated in parentheses. The M : F ratio within each treatment group for 20 mg·kg⁻¹ cisplatin treated shrews in Panel A is: saline-vehicle (4:4), saline-5 CBD (6:6), saline-10 CBD (5:3), WAY100135-vehicle (5:5), WAY100135-5 CBD (4:3), WAY100135-10 CBD (3:5). For Panel B the M : F ratio is: saline-vehicle (3:2), saline-5 CBD (2:3), saline-10 CBD (3:3), WAY100135-vehicle (3:3), WAY100135-5 CBD (2:2) and WAY100135-10 CBD (2:3).

Figure 3

Mean (±SEM) number of gapes elicited by LiCl-paired saccharin solution during the drug-free test trial. During conditioning, rats were pretreated with systemic saline (SAL), WAY100135 (10 mg·kg⁻¹, i.p.) or WAY100635 (0.1 mg·kg⁻¹, i.p.) 15 min prior to systemic vehicle (VEH) or CBD (5 mg·kg⁻¹, s.c.). *P < 0.05, significant difference.

Figure 4

(A) Traces of infusion sites in the DRN (circles) and out of the DRN for animals treated with WAY-CBD (triangles) on drawings of coronal sections. Numbers indicate sections relative to inter-aural zero. (B) A representative photomicrograph of the tip/track of the injector in the DRN.

Figure 5

Mean (±SEM) number of gapes elicited by LiCl-paired saccharin solution during the drug-free test. During conditioning, rats were pretreated with intracranially administered saline or WAY100635 (21 ng) into the DRN 15 min prior to systemic vehicle or CBD (5 mg·kg⁻¹, s.c.) *P < 0.05, significant difference.

Figure 6

(A) Traces of infusion sites in the DRN for all groups (circles). Numbers indicate sections relative to inter-aural zero. (B) A representative photomicrograph of the tip/track of the injector in the DRN.

Figure 7

Mean (±SEM) number of gapes elicited by LiCl-paired saccharin solution during the drug-free test. During conditioning, rats were pretreated with systemic saline (SAL) or WAY100635 (0.1 mg·kg⁻¹, i.p.) 15 min before intracranially administered vehicle (VEH) or CBD (10 µg) into the DRN. *P < 0.001, significant difference.

Figure 8

Effects of 8-OH-DPAT and CBD on specific binding of [³H]8-OH-DPAT to rat brainstem membranes (n= 6). The IC₅₀ and E_max values of 8-OH-DPAT for its displacement of [³H]8-OH-DPAT, with 95% confidence limits shown in parentheses, were 9.6 nM (5.6 and 16.3 nM) and 96.6% (86.8 and 106.5%), respectively. Symbols represent mean values ± SEM.

Figure 9

Effects of (A) 8-OH-DPAT in the presence of DMSO (vehicle; n= 7) or 100 nM WAY100635 (n= 7) and (B) CBD (n= 4) on [³⁵S]GTPγS binding to rat brainstem membranes. Mean EC₅₀ values for 8-OH-DPAT, with 95% confidence limits shown in parentheses were 21.7 nM (7.6 and 61.9 nM), in the presence of vehicle and 1565 nM (390 and 6277 nM) in the presence of WAY100635. Symbols represent mean values ± SEM.

Figure 10

Effect of 8-OH-DPAT on [³⁵S]GTPγS binding to rat brainstem membranes in the presence of DMSO (VEH) or CBD. Mean E_max values for 8-OH-DPAT in panels A, B, C, D and E with 95% confidence limits shown in parentheses were 35.1% (26.6 and 43.5%; n= 8), 34.8% (30.3 and 39.3%; n= 8), 44.3% (33.4 and 55.1%; n= 6), 32.4% (22.8 and 41.9%; n= 10) and 32.0% (22.9 and 41.1%; n= 9), respectively, in the presence of vehicle and 34.0% (22.2 and 45.9%; n= 8), 43.3% (35.5 and 51.0%; n= 6), 51.3% (39.3 and 63.3%; n= 6), 62.3% (51.0 and 73.6%; n= 10) and 28.4% (18.5 and 38.3%; n= 9), respectively, in the presence of 1nM, 10 nM, 31.6 nM, 100 nM or 1 µM CBD. Corresponding mean EC₅₀ values for 8-OH-DPAT were 11.2 nM (1.9 and 66.7 nM), 22.0 nM (9.5 and 50.9 nM), 37.3 nM (8.1 and 173 nM), 12.7 nM (1.2 and 139 nM) and 37.4 nM (6.3 and 222 nM), respectively, in the presence of vehicle and 7.1 nM (0.4 and 126 nM), 45.7 nM (14.1 and 149 nM), 28.6 nM (40.5 and 180 nM), 19.7 nM (2.8 and 139 nM) and 26.2 nM (2.1 and 332 nM), respectively, in the presence of 1nM, 10 nM, 31.6 nM, 100 nM or 1 µM CBD. Symbols represent mean values ± SEM.

Figure 11

Mean (±SEM) number of gapes elicited by LiCl-paired saccharin solution during the drug-free test trial in Experiments A and B. During conditioning, rats were pretreated with systemic CBD (20.5 mg·kg⁻¹ in Experiment A or 00.5 mg·kg⁻¹ in Experiment B) 15 min prior to saline or 8-OH-DPAT (0.05 mg·kg⁻¹ in Experiment A or 0.005 mg·kg⁻¹ in Experiment B). Thirty minutes later, all rats were conditioned with 0.1% saccharin, followed immediately by LiCl. *P < 0.05., significant difference.