Meeting Abstract
Stress levels in laboratory rats have been shown to respond to handling treatments that mimic typical adolescent socialization interactions. Adolescent rats were subjected to physical manipulations to assess their potential impact on stress systems; treatments included tickling, playing, restraint, and minimal handling. Treatments were administered every other day for a three week period, followed by a 2 week period without treatment. Body weights, blood smears, serum samples, and ultrasonic vocalizations were collected throughout all 5 weeks. Delayed-type hypersensitivity (DTH) is a cell-mediated response to an antigen that is introduced into the body. The duration and degree of inflammation can be impacted by stressors which inhibit the immune response. We sensitized rats to 2,4-Dinitrochlorobenzene (DNCB) on the abdomen and later assessed the DTH response on the ear lobes. After DNCB application ear swelling was measured with a caliper at 24, 48, and 72 hours. A DTH test started on day 10 of handling showed significant inflammation in all treatment groups at 48 hours post-application of DNCB, but not at 24 or 72 hours (p<0.0001) indicating similar level and timing of DTH reaction. This effect was not detected during a second DTH test at day 24, however the duration of the inflammatory response was longer in rats which had been tickled or played with (p=0.031). While there was no significant effect of treatment on body weight during the 3 week handling period, rats subjected to restraint were heavier than rats from the playful handling and minimally handled groups at 10 days post-treatment (p=0.006). Taken together, these results suggest that handling by researchers can significantly impact these measures of stress, and we will continue to analyze vocalizations, antibody levels, and circulating blood cell populations.
