Effects of transplantation of fetal hippocampal or hindbrain tissue into the brains of adult rats with hippocampal lesions on water maze acquisition.

Rats were given bilateral aspiration lesions of the hippocampus. Some of these rats then received bilateral transplants of fetal hippocampal or dorsal ventricular ridge tissue that was dissected from embryonic rat brains at 16 or 17 days of gestation. The remaining rats with hippocampal lesions did not receive fetal brain transplants. Rats with neocortical aspiration lesions, but without transplants, and rats without brain damage were also included in the study. All of the rats were trained to find a submerged platform in a Morris water maze. Rats with the fetal brain transplants were more impaired in some measures of maze learning than were rats with hippocampal lesions only. The results indicate that transplants of fetal brain tissue are not always associated with recovery of behavioral function after brain damage and may even increase a lesion-induced behavioral impairment in tasks that require complex cognitive functioning.