Subsensitivity to beta-adrenergic stimulation in atria from rats infested with Syphacia sp.

Abstract

Syphacia sp. is a common intestinal parasite in conventionally-housed laboratory rodents. Although gross lesions are rare in oxyuriasis, it is possible that more subtle changes may develop, which may affect research results. In this study, we analysed the responsiveness to β-adrenergic stimulation by isoproterenol (ISO) of left atria isolated from Syphacia-infested (SYPH) and control, non-infested adult male Wistar rats (CONT). In the non-infested animals, ISO pD2 was not significantly changed by ivermectin treatment. Whereas the maximal inotropic response to ISO was not significantly affected, the pD2 value was decreased in SYPH (7.61 ± 0.09, n = 7, vs 8.21 ± 0.25 in CONT, n = 5, P < 0.05), indicating lower sensitivity to β-adrenergic stimulation. This change was similar to that caused by a classic stressor, namely repeated immobilization, in non-infested rats (IMMO). In this group, ISO pD2 was 7.62 ± 0.14, n = 6 ( P < 0.05 with relation to CONT). The results indicate that infestation with Syphacia sp. is as effective as immobilization at diminishing cardiac reactivity to β-adrenergic stimulation. It is thus possible that oxyuriasis may affect the response of other tissues to physiological modulators.