Dopamine pathways are connected systems of neurons that send dopamine, one of the most influential neurotransmitters, to different parts of the brain. There are four main dopamine pathways that are responsible for creating a variety of brain responses. The mesolimbic and mesocortical pathways are involved with motivation and emotion, and they have been linked to addictive behavior and schizophrenia. The nigrostriatal pathway controls body movements, and damage to this pathway is thought to contribute to the development of Parkinson’s disease. Finally, the tuberoinfundibular pathway is believed to play a role in maternal and nurturing behaviors as well as regulation of hormones.
The mesocortical and mesolimbic dopamine pathways originate in the mid-brain. Dopamine is carried to the frontal cortex by the mesocortical pathway, and the mesolimbic transmits it to the limbic system. These pathways are closely related and are believed to be primarily involved with regulating motivation and emotion. Irregular functioning of these areas of the brain is thought to produce hallucinations and might be a cause of schizophrenia.
The mesolimbic pathway is also sometimes called the reward pathway because of the role it plays in addiction. Alcohol and drugs such as methamphetamine, cocaine, heroin and nicotine are all thought to cause a surge of dopamine through the mesolimbic pathway, producing a euphoric effect. As drug use persists, the brain compensates for these surges of dopamine by reducing the number of available dopamine receptors, causing an addict to need more and more of a drug to produce the same feeling. This effect is known as tolerance, which is a major cause of drug overdoses.
The two other dopamine pathways might also be affected by drug use but are also thought to be involved with controlling other brain responses. The nigrostriatal dopamine pathway is located in the center of the brain and is primarily responsible for gross motor control, or large body movements. The development of Parkinson’s disease is believed to result in part from damage to the neurons in this area of the brain.
The final type of dopamine pathway, the tuberoinfundibular pathway, transmits dopamine from the hypothalamus to the pituitary gland. The most well-known function of this pathway is hormone regulation. It regulates the release of a hormone from the pituitary gland called prolactin and is related to maternal responses and hormonal changes during pregnancy.