['To hibernate fetal ventral mesencephalic tegmental (VMT) cells from Spraque-Dawley rats E-15 for 5 days at 4 degrees C in either hibernation media (HM) or in conditioned hibernation media (CHM) supplemented with trophic factors such as epidermal growth factor (EGF 200 ng/ml), basic fibroblast growth factor (bFGF 100 ng/ml), recombinant human brain derived neurotrophic factor (rhBDNF 20 micrograms/ml), recombinant human glial cell-derived neurotrophic factor (rhGDNF 20 micrograms/ml), fetal calf serum (FCS 9%), or human placental cord serum (HPCS 10%).', 'The percent of cell viability and the density of tyrosine hydroxylase immunoreactive (THir) cells in fetal striatal-VMT co-culture were determined.', 'The viability of fetal striatal cells (0.8 +/- 0.104) was slightly higher than that of fetal VMT cells (0.7 +/- 0.072) at 0-time point (F17,1 = 4.677; P = 0.045). After 5 days of hibernation, the viability of fetal VMT cells reduced by 30% (F7,1 = 88.493; P < 0.001) in HM. However, THir-cell density reduced by more than 90% as compared to the freshly harvested VMT cells (F7,1 = 179.944; P < 0.001). CHM with HPCS, bFGF, EGF, BDNF, and GDNF showed higher THir-cell density than that of HM or CHM supplemented with FCS (P < 0.001).'] Do neurotrophic factors increase tyrosine hydroxylase immunoreactive cell density of fetal mesencephalic cells?