Loss OfAutonomic Neurons Results in the Hypersensitivity of the Target Organ to Transmitter

When the postganglionic neuron to a target organ is lost, the smooth muscle of that organ becomes hypersensitive to any transmitter circulating in the blood. For example, the arterioles of the skin are usually under some adre­nergic stimulation, which results in some vasoconstriction. If the postganglionic adrenergic neuron to the skin is destroyed, vasodilation occurs. However, if norepinephrine is injected into the blood supply to this area of skin, a dramatic (hypersensitive) vasoconstriction occurs. This is thought to be caused, at least in part, by an increase in numbers of postsynaptic receptors at the denervated synapse.