Transplantation of fetal medial preoptic area tissue into adult brain-injured rats: a behavioral, physiological, and anatomical study
Description
Previous research has identified the medial preoptic area (MPOA) as being critically involved in the mediation of masculine copulatory behavior in mammals. Other research has shown that fetal brain tissue can be transplanted successfully into the brains of adult mammals. The present study sought to determine whether copulatory behavior could be restored in males bearing MPOA lesions by fetal MPOA tissue transplanted into the midbrain. Of 5 rats receiving total MPOA lesions and fetal MPOA transplants, 3 recovered copulatory behavior. Of 3 rats receiving total MPOA lesions and fetal cerebral cortical transplants, one recovered copulatory behavior. Behavioral differences between the two groups were not statistically significant. However, the mean intromission frequency for MPOA-transplanted animals (M = 6.8, SD = 5.25) was greater than that for cerebral cortical-transplanted animals (M = 2.22, SD = 5.25). Yohimbine significantly increased mean intromission frequencies for both groups compared with pre- and post-yohimbine saline tests. However, baseline responding on control test days may have been unusually low. Thermoregulatory adaptation to a cold environment (5(DEGREES)C) by these animals was in the normal range, in marked contrast to what is commonly reported for animals bearing MPOA lesions. This discrepancy may be due to recovery of function mediated by a nonspecific transplant action, or to sparing of function due to dorsal placement of lesions. Some MPOA- and cerebral cortical-transplanted animals displayed motor symptoms following transplantation which could not be accounted for by encroachment of the transplant on the substantia nigra. The transplants may have innervated motor areas abnormally, thus producing motor symptoms. In any case, this is the first report of detrimental effects of transplanted fetal brain tissue. One hundred percent of the transplants survived the 8-week duration of the experiment and contained healthy neurons. Numerous LHRH-immunoreactive axons (but few perikarya) were detected in MPOA but not cerebral cortical transplants. It is concluded that the MPOA transplants displayed the characteristics of transplants which have been shown to modify brain function, but that the small sample sizes may have prevented the detection of any such effects