[Age-related changes in the sympathetic innervation of effector organs in the rat after partial sympathectomy with guanethidine].

Guanethidine (30 mg/kg daily for first 15 days of life) decreased by 85% the amount of cells in the rat upper cervical sympathetic ganglion for 4 months. In ageing, the volume of the ganglion's cells, the density of adrenergic fibers and the noradrenaline content in the heart, intestine and ductus deferens increased in the desympathized animals. The neural cells remaining after desympathization seem to develop a growth of axons and to restore to some extent the density of sympathetic innervation of the periphery. The firing rate of single preganglionic fibers of the cervical sympathetic nerve is increased in the desympathized animals. The increased firing rate seems to be the cause of changes in the surviving neurons.