|Dopamine is responsible for fundamental brain functions. Dopamine dendrites extend into various regions of the brain, controlling different functions through the stimulation of α and β adrenergic and dopaminergic receptors. Dopamine is a neurotransmitter that affects a wide variety of brain processes, many of which are involved in the control of movement, the formation of emotional
responses, and the perception of pain and pleasure. In the frontal lobes, dopamine controls the flow of information from other areas of the brain. Dopamine disorders in this region of the brain can cause a decline in neurocognitive function, particularly those linked to memory, attention and problem solving. This function is particularly related to the mesocortical dopamine pathway.
Dopamine is a sympathomimetic catecholamine which exhibits alpha adrenergic, beta adrenergic, and dopaminergic agonism. Dopamine is the immediate metabolic precursor of norepinephrine and adrenaline. Dopamine can have either an excitatory or inhibitory effect on the postsynaptic potential. When dopamine leaves the presynaptic neuron and goes into the synapse, it can then bind to receptors on the postsynaptic neuron. After dopamine is bound to the postsynaptic cell, it can either facilitate an action potential or inhibit it. A neuron that classically releases dopamine is called a dopaminergic neuron. A series of neurons that are connected by synapses forms a pathway called a dopaminergic pathway. Neurons that make dopamine are damaged in Parkinson's disease, and the symptoms of the disease are caused by dopamine lack.
Dopamine plays a significant role in the cardiovascular, renal, hormonal, and central nervous systems. Dopamine is useful in the management of states of low cardiac output, associated with compromised renal function as with cardiogenic and hypovolemic shock. Dopamine also causes the release of norepinephrine from nerve terminals, which contributes to its effects on the heart. Dopamine usually increases the systolic and pulse pressure and either has no effect on the diastolic blood pressure or increases it slightly. Dopamine produces positive chronotropic and inotropic effects on the myocardium, resulting in increased heart rate and cardiac contractility. Aside from controlling movement, dopamine is also greatlyinvolved in feelings of reward and alertness and purposeful behavior.
Dopamine is commonly associated with the 'pleasure system' of the brain, providing feelings of enjoyment and reinforcement to motivate us to do, or continue doing, certain activities. Certainly dopamine is released by naturally rewarding experiences such as food, sex, use of certain drugs and neutral stimuli that become associated with them. This theory is often discussed in terms of drugs which seem to directly or indirectly related to increase dopamine in these areas, and in relation to neurobiological theories of addiction, which argue that these dopamine pathways are pathologically altered in addicted persons. The mechanism of cocaine and amphetamine is different. Cocaine is acting as dopamine transporter blocker to competively inhibit dopamine uptake to increase the lifetime of dopamine, while amphetamine is acting as a dopamine trasnportet substrate to competively inhibite dopamine be uptaken and increase the dopamine efflux via dopamine transporter.