The availability, storage and transportation of donor tissue are major practical problems associated with the potential use of grafted neural cell replacements in neurodegenerative diseases. The capacity to collect and maintain viable fetal neural tissue would facilitate possible clinical applications, and provide opportunities to study various neural diseases. In the present study, we examined the effect of cool storage on the survivability of intraventricular rat fetal ventral mesencephalic grafts (gestational days 15). In all experiments, fetal ventral mesencephalons were dissected out under a dissecting microscope in calcium-free magnesium-free buffer (CMF: 0.15 M NaCl, 0.008 M Na2HPO4, 0.0027 M KCl, 0.0015 M KHPO4, 0.026 M NaHCO3, with 0.1% glucose, 100 micrograms/ml streptomycin, 2.5 micrograms/ml fungizone). Fetal mesencephalic tissue was grafted into the lateral ventricle following pregraft refrigeration in calcium-free magnesium-free buffer at 4 degrees C. Fetal mesencephalic tissue was hibernated for 5, 12, 16, 20, 24, 28, 32 hours (group A, B, C, D, E, F and G, respectively). As a control group, fetal mesencephalic tissue was grafted into the lateral ventricle immediately after dissection. Grafted fetal mesencephalic tissue which had been hibernated for 16 hours or less survived well. There were no significant decreases in the size of grafts among group A, B, C and the control group. In group A, B, C and the control group, clusters of TH-positive neurons and dense networks of neuritic profiles within the grafts provided a morphological appearance reminiscent of the dendritic bundles that characterize the zone reticulate of the substantia nigra in situ.(ABSTRACT TRUNCATED AT 250 WORDS)