The Effects of Tail Biopsy for Genotyping on Behavioral Responses to Nociceptive Stimuli

Abstract

Removal of a small segment of tail at weaning is a common method used to obtain tissue for the isolation of genomic DNA to identify genetically modified mice. When genetically manipulated mice are used for pain research, this practice could result in confounding changes to the animals' responses to noxious stimuli. In this study, we sought to systematically investigate whether tail biopsy representative of that used in standard genotyping methods affects behavioral responses to a battery of tests of nociception. Wild-type littermate C57BL/6J and 129S6 female and male mice received either tail biopsies or control procedural handling at Day 21 after birth and were then tested at 6–9 weeks for mechanical and thermal sensitivity. C57BL/6J mice were also tested in the formalin model of inflammatory pain. In all tests performed (von Frey, Hargreaves, modified Randall Selitto, and formalin), C57BL/6J tail-biopsied animals' behavioral responses were not significantly different from control animals. In 129S6 animals, tail biopsy did not have a significant effect on behavioral responses in either sex to the von Frey and the modified Randall-Selitto tests of mechanical sensitivity. Interestingly, however, both sexes exhibited small but significant differences between tail biopsied and control responses to a radiant heat stimulus. These results indicate that tail biopsy for genotyping purposes has no effect on nocifensive behavioral responses of C57BL/6J mice, and in 129S6 mice, causes only a minor alteration in response to a radiant heat stimulus while other nocifensive behavioral responses are unchanged. The small effect seen is modality- and strain-specific.

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“…Microtattoo is the least noxious marking technique, with microtattoed animals having significantly lower heart rate and blood pressure than animals that were given ear tattoos or ear notching (Kasanen et al, 2011). Furthermore, the more traumatic practice of tail biopsy for genotyping has no effect on pain behaviors (Morales and Gereau, 2009). These studies suggest that the less invasive technique of microtattooing likely had no effect on behavior, apoptosis, or cell counts in our study.…”

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“…The threshold was determined in 3 trials per hind paw with a 15 minute interval between trials. Tail mechanical sensitivity was measured with an Analgesia-Meter (Ugo Basile; Stoelting) using a modification of the Randall-Selitto test as previously described (Morales and Gereau, 2009). The withdrawal threshold was obtained by averaging the values obtained in 3 trials which were separated by 15 minutes.…”