Task dependent rate of recovery following serial posterior hypothalamic lesions

Forty-two male rats received one-stage or sequential unilateral (30 days between sides) lesions of the posterior hypothalamus and were tested 1, 3 and 5 weeks later on a swimming task and in the open field. Subjects with serial lesions were comparable to sham-operated rats in swimming ability at each observation point. Rats with one-stage lesions, in contrast, showed pronounced swimming deficits (time under water, body angle, hindlimb kicks/sec) at each test session, although some improvement was noted over time. With respect to open field activity, subjects with serial lesions did not demonstrate significant recovery until the third postoperative week, while rats with one-stage lesions were impaired at each test session. These data show that serial lesions of the posterior hypothalamus may be associated with more rapid recovery of function than one-stage lesions, but that the time course for such recovery may vary with the specific ability being evaluated.