C57BL/6 mice, in contrast to BALB/c mice, display minimal behavioral changes in response to environmental stressors and are considered relatively stress-resistant. We have shown that application of acute restraint prior to chemical challenge enhanced cutaneous hypersensitivity (CHS) in BALB/c mice and that this enhanced response is partially glucocorticoid dependent. Due to strain differences in the immune response and in the response to environmental stressors, we hypothesized that acute restraint would not enhance CHS in the less stress-sensitive C57BL/6 mice. We sensitized and challenged C57BL/6 mice with the contact sensitizer, 2, 4-dinitrofluorobenzene (DNFB) in the presence and absence of restraint. Acute restraint, applied prior to chemical challenge, significantly increased serum corticosterone, but to concentrations approximately 60% of those reported for BALB/c mice. Neither restraint nor the exogenous administration of corticosterone enhanced chemical-induced ear swelling in C57BL/6 mice. Pharmacological interruption of the hypothalamic pituitary adrenal axis (HPAA) with the glucocorticoid type II receptor antagonist, RU486, did not alter the development of CHS, however, adrenalectomized (ADX) mice exhibited decreased ear swelling, a measurement that was decreased further by restraint. Combined application of acute restraint and corticosterone prior to chemical challenge significantly enhanced the ear swelling response in C57BL/6 wild-type mice. These data confirm that C57BL/6 mice have a blunted corticosterone response to restraint and that acute restraint does not modulate cutaneous hypersensitivity. Furthermore, our data demonstrate that stress-resistance is not conferred exclusively through the glucocorticoid pathways.
Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, 1095 Willowdale Road, MS 3014, Morgantown, WV 26505