Question to the Home Office:

To ask the Secretary of State for the Home Department, with reference to project 1 entitled Defining the role of G protein coupled receptors in the brain and the therapeutic potential of targeting these receptors in neurological disease and addiction, in her Department's document entitled Non-technical summaries for project licences granted October – December 2025 that require a retrospective assessment, published in February 2026, what assessment she has made of the scientific relevance to humans of injecting opioids into the veins of mice and then dipping the tail of some mice into hot water .

This project, among other research, sits within the Government’s broader strategy to support research that advances the understanding of major public health challenges – including addiction and neurodegenerative disease.

The non-technical summary for this research project is available at: https://www.gov.uk/government/publications/non-technical-summaries-granted-in-2025.

The use of mice and the procedures in question were assessed as appropriate and scientifically justified because they allow researchers to study learning, memory, reward-related behaviour and withdrawal symptoms in a way that cannot be replicated using non-animal methods alone.

All project licence applications under the Animals (Scientific Procedures) Act 1986 (ASPA) are assessed by medically or veterinary qualified inspectors within the Animals in Science Regulation Unit (ASRU). Under ASPA, no project can be granted without a harm-benefit analysis, where an ASRU inspector makes a rigorous assessment of the scientific rationale, and must assess that the harms of the proposed project are justified by the likely benefits.

The project must also demonstrate full application of the legal requirements of replacement, reduction and refinement (the 3Rs). This means that animal use cannot be approved if a practicable non-animal alternative method exists, the number of any animals used must be minimised, and the most refined methods must be used for animal testing to minimise harms.