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Development and validation of a new preclinical analgesic assay

University of British Columbia

Current preclinical analgesic assays suffer from major weaknesses that hamper the discovery of new drugs. This thesis describes the development of a new mouse assay, the Hypertonic Saline Analgesia Assay (HSAA). Chapter 1 provides an overview for current preclinical analgesic assays and discusses their strengths and weaknesses. It also discusses the impact of sex, strain, and circadian rhythm on nociception and antinociception. Chapter 2 describes the development of the assay. We evaluated hypertonic saline (HS) as a nociceptive agent, its optimal concentration, the responses, and the optimal time for evaluation. We also assessed sex related differences and tissue damage. Chapter 3 describes the validation of the assay. Analgesics known to be effective clinically were assayed to establish the validity of the HSAA. HSAA demonstrated that responses were attenuated by a range of clinical analgesics, produces minimal tissue damage and has lower variability compared to other assays. Chapter 4 examines the refinement of the assay. We determined the effects of repeated testing, strain, sex, and diurnal rhythm on the reproducibility of HSAA. The absence of tissue damage raised the possibility of repeated testing in a mouse to reduce the number of animals. The antinociceptive action of morphine was unchanged when HSAA was used at different times in the same hind paw of a mouse. No histological damage was observed following multiple injections of HS. Repeated testing in the same mouse reduces both the number of animals required and the variance of the results. Initial development and validation were performed with CD-1 mice. To evaluate the widespread utility of HSAA, we evaluated its ability to detect analgesics in another commonly used murine strain, C57BL/6. HSAA detected the dose-dependent attenuation of responses by morphine in C57BL/6 which was equivalent to responses found with CD-1 mice. Additionally, female mice were demonstrated to have greater response than males. The diurnal cycle had little effect. In conclusion, the HSAA rapidly detects standard analgesics and is reproducible within an animal and between strains. This assay minimizes tissue damage and the number of animals required. HSAA is a useful addition to the armamentarium of preclinical analgesic assays.  

Text

2020-08-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/67109

Pharmacology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/