A method for the measurement of growth of noradrenergic axons in tissue culture and the effects of colchicine thereon.

Explants of superior cervical ganglia from 2-day-old mice have been cultured on collagen-coated glass coverslips in modified L15 culture medium (with foetal calf serum) for 5-day periods. Noradrenergic axons were visualized by uptake of alpha-methyl noradrenaline and subsequent treatment with buffered 2% glyoxylic acid for fluorescence microscopy. An index of axon growth was obtained by a point-counting method using a coherent multi-purpose test system graticule. The growth indices thus obtained for a sample of control cultures were normally distributed. Examination of a single batch of cultures showed that good agreement was obtained between successive counts by one observer and between counts by two observers. The method gave sufficient resolution to detect with statistical significance a small inhibition of growth by colchicine at 2 ng/ml and to obtain a concentration-effect plot for this drug. The acceptability of the method for routine use is discussed.