Hypothalamic dopaminergic neurons inhibit prolactin secretion and lead to the use of agonists in inhibiting lactation . There are a number of drugs which interact presynaptically with dopamine terminals including reserpine , amphetamine , MAO inhibitors , and cocaine . This forms the basis for the administration of the dopamine precursor, l-dopa as replacement therapy, dopamine agonists , and drugs which indirectly facilitate dopamine activity. Dopaminergic neurons are found in the hypothalamus which increase the secretion corticotropin and growth hormone and inhibit the release of prolactin. Despite the effects of l-dopa in increasing growth hormone, acromegaly does not occur.
Dopamine is synthesized by a two step process from the l-amino acid tyrosine.
Although there are inhibitors of both enzymes, none are useful clinically. This reaction does not effect the termination of action of dopamine in the synapse, and there are no important inhibitors of the enzyme. Monoamine oxidase is found within mitochondria in the neuron terminal and serves to regulate intracellular stores of dopamine. This is a non-specific enzyme which oxidatively deaminates other monoamines such as norepinephrine and serotonin. Inhibitors of this enzyme increase the intraneuronal stores of all three monoamines.