Abstract

Abstract ID 95376

Poster Board 503

Cannabinoids offer a promising analgesic treatment option for a variety of pain conditions, but their chronic use leads to the development of tolerance to the antinociceptive effects, posing a problem to their utilization as an effective long-term therapeutic. Agonist-induced internalization of cannabinoid receptor 1 (CB1R) is a crucial component in regulating signal transduction and the C-terminus tail of CB1R serves as a regulatory domain for internalization. Six point mutant (6PM) mice express serine/threonine to alanine point mutations for six putative G protein-coupled receptor kinase (GRK) phosphorylation sites in the C-terminus tail of CB1Rs that are necessary for internalization, thereby making the CB1Rs unable to efficiently undergo internalization, trafficking, and resensitization. The objective of this study is to investigate the effect of CB1R internalization on sensitivity to the acute antinociceptive and hypothermic effects of cannabinoid agonists as well as assessing recognition memory and motor coordination in 6PM mice expressing an internalization-deficient form of CB1R. A cumulative dose response curve was used to assess the acute response to CP55,940, a strongly internalizing cannabinoid agonist. Antinociception was measured using the tail-flick test and cannabinoid-induced hypothermia was examined by recording core body temperature. Motor coordination was assessed using the rotarod test where the latency to fall was measured. Recognition memory was evaluated using the novel object recognition (NOR) test where novel object recognition was determined by measuring time exploring a familiar versus a novel object placed in the test arena. 6PM mice show decreased antinociceptive and hypothermic responses to the effects of CP55,940 compared to wild-type controls. 6PM mice also displayed a decrease in recognition memory by spending more time exploring the familiar object, rather than the novel object in the novel object recognition test relative to wild-type controls. There were no differences between wild-type and 6PM mice in the average time spent on the rotarod. Data from this study demonstrate that the antinociceptive and hypothermic effects of CP55,940 were reduced in the 6PM mice suggesting that CB1R internalization, trafficking, and recycling may be important components involved in the response to cannabinoids. This data also shows that six point mutant mice have a lower recognition memory, indicating a possible role for CB1R internalization in cognitive processes. Overall, these results suggest that internalization may be a critical regulator of responses to cannabinoids as well as playing a role in memory formation and recall pathways.

Acknowledgements Funded by NIH grant DA044999 and the NASA West Virginia Space Grant Consortium, Grant # 80NSSC20M0055.