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

Insulin and insulin-like growth factor I enhance regeneration in cultured adult rat sensory neurones

Insulin and the insulin-like growth factors (IGFs) may directly affect the growth, development, and maintenance of the vertebrate nervous system. Previous in vitro studies have focused on embryonic nervous tissue. In this study the effects of insulin, IGF-I, IGF-II and nerve growth factor (NGF) on regeneration and neuronal survival were studied in cultured adult rat sensory neurones in a cell culture environment that limited non-neuronal cell mediated effects. Regeneration, as assessed by neurite outgrowth, was significantly enhanced by insulin and IGF-I in a dose-dependent manner. The half-maximally effective concentrations, ED50's, were approximately 1 nM and 0.1 nM for insulin and IGF-I, respectively. Concentrations of IGF-I as low as 10pM were active. There was some evidence that IGF-II stimulated regeneration, although this failed to reach statistical significance. NGF also promoted regeneration, confirming previous studies, exhibiting an ED50 of approximately 0.3 ng/ml and inducing a maximal response 2-fold greater than that observed with insulin or IGF-I. Combined treatment with NGF and insulin had an additive effect. Specific anti-NGF antiserum inhibited the regenerative response to NGF but failed to block the response to IGF-I, supporting the view that IGF-I was acting directly on sensory neurones rather than stimulating NGF production by non-neuronal cells. Insulin, IGF-I and NGF had no effect on neuronal survival in this culture system. These results show that adult sensory neurones can respond with enhanced regenerative growth to insulin and IGF-I, in addition to NGF although the response to IGF-II was less clear.

Colchicine effect on B-50/GAP43 phosphoprotein localization in rat dorsal root ganglion explants

In rat embryonic dorsal root ganglion explants stimulated by nerve growth factor, the neuron-specific phosphoprotein B-50 (GAP43) is primarily localized in the distal portion of outgrowing neurites. Addition of colchicine leads to a decrease in total amount of B-50 and a marked redistribution in the neurons. The data underscore the role of axonal transport in the concentration of B-50 in growth cones of growing neurites.

The regrowth of right atrial noradrenergic nerves after 6-hydroxydopamine in genetically diabetic mice; effects of insulin treatment

1 This study examined the rate of repletion of right atrial noradrenaline levels after a single dose (100 mg/kg i.p.) of 6-hydroxydopamine (6-OH Da) in diabetic and non-diabetic mice of the C57 BL/KS db/db strain. 2 In mice which received no 6-OH Da there was no significant difference, in endogenous noradrenaline levels, between diabetic and non-diabetic animals. The depletion of noradrenaline 24 h after 6-OHDa was slightly more profound in the diabetic mice than in non-diabetic controls. Thereafter the rate of repletion of noradrenaline was more rapid in the diabetic group. 3 The normal noradrenaline content was reinstated in diabetic mice between 7 and 10 days after 6-OHDa. In the non-diabetic group levels similar to those found in untreated mie were not reinstated until 14 days after 6-OHDa. 4 Ten days after 6-OHDa right atria from diabetic mice were markedly more responsive to stimulation of the intramural noradrenergic nerves than were preparations from non-diabetic mice. 5 A group of diabetic mice was treated with insulin (10 m Units/g daily) for 6 weeks. The right atria from these animals, examined 10 days after 6-OHDa, were similar in their responses to noradrenergic nerve stimulation to the preparations from the non-diabetic mice. 6 All these groups of atria gave similar responses to exogenous noradrenaline. These findings indicate that regrowth of noradrenergic terminals after 6-OHDa was more rapid in diabetic mice than in either insulin-treated diabetic mice or non-diabetic mice.

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.