Investigation of potential applications of odorant receptor (OR) 37 ligands in mice and animal welfare refinement.

Abstract

Members of the evolutionary conserved odorant receptor (OR) 37 family of mouse olfactory receptors are known to have an unusual direct projection to the paraventricular nucleus (PVN) of the hypothalamus, via the main olfactory bulb. Previous research has shown that the mixture of three OR37 ligands were effective in reducing the activation of the neurons in the PVN following novel cage exposure, similar to conspecifics’ natural secretion. This effect suggests that the OR37 ligands may play a role in reducing the stress axis response by a potential social buffering effect via olfactory cues. This study investigates the acute exposure of the OR37 ligands’ effect and shows that the reduction of the PVN activation could be done in different anxiogenic tests without affecting the behaviours and the endocrine responses.

Laboratory conditions and environments have been known to be a source of stressors for mice: by socially isolating the mice, which potentially reduces the amount of olfactory cues exposure, by routine handling, and by an ambient laboratory temperature that does not reflect mice's thermoneutral zone. This investigation then explores the chronic application of the OR37 ligands as a potential enrichment for socially isolated mice and showed a buffering effect on the social isolation-induced temperature change without other behavioural changes due to the lack of social isolation-induced changes. Finally, this investigation explores other husbandry refinements including mice preference towards housing temperature to group nesting size preference, and mouse stress responses to tail-handling. The investigation on the housing temperature preference showed a negative correlation to the group nesting size preference, while the tail-handling responses did not show a change in affect but to overt behaviours associated with anxiety-related state. Although further studies will be needed before drawing any significant conclusions, this thesis provides preliminary data towards better understanding of the OR37 system and of animal welfare refinement.

Date of Award	11 May 2021
Original language	English
Awarding Institution	The University of Bristol
Sponsors	Indonesian Endowment Fund for Education (LPDP) -Ministry of Finance of the Republic of Indonesia
Supervisor	Peter A Brennan (Supervisor) & Emma S J Robinson (Supervisor)