Hyposensitivity of smooth muscle to noradrenaline caused by sympathetic hyperinnervation.

MUCH research has been carried out on the effects of nerve growth factor (NGF)1–3, a polypeptide substance4,5 which enhances the proliferation and ripening of neuroblasts in spinal and sympathetic neurons6,7. After injection of NGF into a newborn animal, a considerable increase occurs in the number and size of nerve cell bodies in sympathetic ganglia6,7 as well as the number of centrifugal sympathetic axons and the density of endings in numerous effector organs6,8,9.