Sensitivity to foot shock in autoimmune NZB x NZW F1 hybrid mice.

Prior studies have demonstrated deficits in active avoidance learning in young (12-week-old) mice that develop lupus-like autoimmunity. Because foot shock is the motivating stimulus in this task, sensitivity to foot shock was assessed in autoimmune NZB x NZW F1 hybrid (B/W) and nonautoimmune NZW female mice. Responses to shock at levels ranging from 0.05 to 1.6 mA were recorded twice during the development of autoimmunity. At 12 weeks of age, B/W mice did not differ from NZW mice in sensitivity to shock. However, at 24 weeks of age, when antibody levels were elevated, sensitivity to foot shock decreased in B/W mice at low shock levels and increased at high shock levels. A neurological battery revealed no deficits that could account for these effects. However, IgM anti-DNA antibody levels were positively correlated with responsiveness to high levels of shock. The change in the pattern of sensitivity at 24 weeks may be due to a combination of disease-related sensory impairment at low shock levels and hyperalgesia at high shock levels. The response to high levels of shock may also be an indication of enhanced emotionality, an interpretation consistent with reports in other lupus-prone strains and affective disorders in humans with lupus.