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Nerve fibre outgrowth from sympathetic ganglia of the newborn rat in organotypic cultures: effect of heart auricle co-cultures, fetal calf serum and collagen.

Sympathetic thoracic chain ganglia of 3-day-old rats were cultured for 24 hours alone or together with heart atrium explants in collagen gel media containing supplemented Medium 199 with no, 1% or 20% fetal calf serum. The amount of nerve fibres growth was estimated by counting the number of intersections of the fibres and a line ladder in the ocular. In the presence of serum the nerve fibre outgrowth in all directions was greatly stimulated by atrium co-cultures. The total mass of nerve fibres growing toward the atrium was significantly larger than in the other three directions. If no serum was added to the medium, the nerve fibre growth was scanty even in co-cultures, and there was no significant directional growth toward atrium explants. Nerve fibres grew much faster in the gel-containing Medium 199 than in an aqueous Medium 199. It is concluded (1) that atrial explants stimulate sympathetic nerve fibre growth by releasing a growth-promoting substance, which forms a concentration gradient in the gel medium, and (2) that fetal calf serum is required in the medium to obtain such a stimulating effect.