Ultrastructural changes in sympathetic neurons of newborn and adult mice treated with nerve growth factor

Purified nerve growth factor (NGF) induces a marked hypertrophy of the sympathetic chain ganglia when injected into newborn and adult mice. A 5-day treatment of newborn or adult mice with daily injections of NGF (20 μg/g body weight) results in both instances in a striking increase in wet weight of sympathetic ganglia. When examined at the electron microscope, the NGF—treated neurons appear very enlarged: the endoplasmic reticulum and free ribosomes are very abundant. The cytoplasmic area is filled with the interlacing bundles and threads of neurofilaments. This extraordinary production of neurofilaments and neurotubuli appears to be the most striking feature of the NGF—treated neurons.