DOPAMINERGIC DRUGS DOPAMINE D2 RECEPTOR AGONISTS: PRAMIPEXOLE, BROMOCRIPTINE MECHANISM OF ACTION • Acts on D2 receptors, which are Gi PCRs, when activated can induce inhibitory effects onto the target cell • Can act at the striatal neuronal cells of the striatum of the basal ganglia of the indirect pathway, in order inhibit the pathway, thus preventing turning down of movement by the basal ganglia. • Also inhibits lactotroph cell growth, reducing size of adenoma and inhibit secretion of prolactin. INDICATION: • Parkinson’s Disease, treatment of extrapyramidal side effects of traditional neuroleptics, treatment for hyperprolactinemia and prolactinoma
DOPAMINE D2 RECEPTOR ANTAGONISTS (NEUROLEPTICS): CHLORPROMAZINE, CLOZAPINE, RISPERODONE, ETC. MECHANISM OF ACTION • Acts as a blocker of D2 receptors, resulting in acute effects of increased dopamine release from dopaminergic neurons. • Therapeutic effects come from chronic use, where excessive dopamine excitation of D1 receptors result in tachyphylaxis of the receptor, resulting in the downregulation of D1 receptors, reducing firing from neurons. • Many of these drugs also have blockade effects on other receptors, resulting in other therapeutic effects (e.g., 5-HT2A block for treatment of drug induced psychosis) INDICATION: • Psychosis and Manic Episodes (Reduces Dopaminergic neuron firing in the long term)
