Differing effects on superior cervical ganglia in neonatal mice produced by antisera to nerve growth factors from mice and snakes.

Rabbit or horse antisera to Nerve Growth Factors from mouse salivary glands and the venoms of five snakes were injected into neonatal mice. The mice were killed 10 days later and the superior cervical ganglia removed, weighed and examined histologically. Treatment with antisera to the snake Nerve Growth Factors had no effect on ganglion weight, maximum neuronal density or mean neurone diameter. This was true even for the one antiserum that in vitro showed a weak cross-reactivity with the mouse antigen. In contrast, treatment with the antiserum to mouse Nerve Growth Factor produced a partial destruction of the superior cervical ganglia (immunosympathectomy). The weights of the ganglia in animals treated for the first 5 days post partum with increasing volumes (a total of 0.5 ml) of antiserum to the mouse factor fell by some 80% the total neurone number by approx 50% the maximum neurone density by 40% and the mean neurone dia. by 17%. The effect was found to be dose dependent.It is considered that caution is required in extrapolating results from in vitro studies on Nerve Growth Factor to the situation obtaining in vivo and that the inability of snake antisera to produce immunosympathectomy in neonatal mice may result from differences in the antigenic determinants of the mouse and snake Nerve Growth Factors. The marked effect of antiserum to the mouse salivary gland factor in neonatal mice reported by earlier workers has been confirmed. No single explanation, however, can be given for the differences in the reduction in neurone numbers found in the present and previous studies. Furthermore, it is concluded that neither the previous nor the present studies afford evidence that the antiserum directly causes neuronal death.