You can think of a brain pathway as a power line that connects two brain regions. Brain pathways are made up of interconnected neurons along which signals are transmitted from one brain region to another.
Brain region 1
Brain region 2
Brain region 3
Interconnected neurons form brain pathways which allow communication between different brain regions.
Dopamine is the neurotransmitter used by the reward pathway (also called the mesolimbic pathway, which is closely associated with the mesocortical pathway). But there are two other important pathways in the brain that utilize dopamine: the nigrostriatal pathway and the tuberoinfundibular pathway. Generally, drugs that affect dopamine levels in the brain affect all three of these dopamine pathways.
Substantia Nigra to Striatum
. Motor control
. Death of neurons in
this pathway can result in
Hypothalamus to Pituitary gland
. Hormonal regulation
. Maternal behavior (nurturing)
. Sensory processes
Mesolimbic and Mesocortical pathways
Ventral Tegmental Area to Nucleus
Accumbens, Amygdala & Hippocampus,
and Prefrontal Cortex
. Motivation and emotional response
. Reward and desire
. Can cause hallucinations and schizophrenia if not functioning properly
Dopamine and another neurotransmitter called Serotonin are released by a small number of neurons in the brain. But each of these neurons connects to thousands of other neurons. For this reason, dopamine and serotonin have a great deal of influence over complex brain processes.
Serotonin is another neurotransmitter that is affected by many of the drugs of abuse, including cocaine, amphetamines, LSD, and alcohol. Serotonin is produced by neurons in the Raphe nuclei. Raphe nuclei neurons extend processes to and dump serotonin onto almost the entire brain, as well as the spinal cord. Serotonin plays a role in many brain processes, including regulation of body temperature, sleep, mood, appetite and pain. Problems with the serotonin pathway can cause obsessive-compulsive disorder, anxiety disorders, and depression. Most of the drugs used to treat depression today work by increasing serotonin levels in the brain.
To Spinal Cord
Glutamate and GABA (gamma-aminobutyric acid) are the brain's major "workhorse" neurotransmitters. Over half of all brain synapses release glutamate, and 30-40% of all brain synapses release GABA.
Since GABA is inhibitory and glutamate is excitatory, both neurotransmitters work together to control many processes, including the brain's overall level of excitation. Many of the drugs of abuse affect either glutamate or GABA or both to exert tranquilizing or stimulating effects on the brain.
Alcohol decreases glutamate activity
Caffeine inhibits GABA release
"angel dust" increases glutamate activity
Caffeine increases glutamate activity
Alcohol increases GABA activity
Tranquilizers increase GABA activity
GABA and glutamate regulate action potential traffic. GABA, an inhibitory neurotransmitter, stops action potentials. Glutamate, an excitatory neurotransmitter, starts action potentials or keeps them going.