INTERLEUKIN-6 IMPROVES THE SURVIVAL OF MESENCEPHALIC CATECHOLAMINERGIC AND SEPTAL CHOLINERGIC NEURONS FROM POSTNATAL, 2-WEEK-OLD RATS IN CULTURES

Interleukin-6 (human recombinant) supported the survival of cultured mesencephalic, catecholaminergic and septal cholinergic neurons from postnatal, two-week-old (P13-P15) rats. Significantly, more catecholaminergic neurons, stained by monoclonal anti-tyrosine hydroxylase antibody, were found in cultures supplemented with interleukin-6 at a concentration of 5 ng/ml than in cultures not treated with interleukin-6. The optimal dose used was 50 ng/ml. The survival effect of interleukin-6 on postnatal rat, tyrosine hydroxylase-positive neurons was observed both in cultures using serum-containing and serum-free medium. Contents of dopamine and noradrenaline in cultures with interleukin-6 were also larger than in control cultures. Interleukin-6 also increased the survival of cultured embryonic (E17) rat midbrain tyrosine hydroxylase-positive neurons. The effect on these neurons was, however, smaller, and the optimal dose of interleukin-6 was nearly 5 ng/ml. Interleukin-6 also supported the survival of cultured postnatal (P13) rat septal cholinergic neurons, visualized by acetylcholinesterase staining. The concomitant addition of mouse nerve growth factor (100 ng/ml) and interleukin-6 (50 ng/ml) had a synergetic effect on the survival of acetylcholinesterase-positive neurons in culture. Our data suggest that the survival of cultured tyrosine hydroxylase-positive, mesencephalic, and acetylcholinesterase-positive, septal neurons from postnatal two-week-old rats was supported by interleukin-6, just as there was a different dose dependency of interleukin-6 on the cultured postnatal neurons compared with embryonic neurons.