Dopamine
Dopamine is a neurotransmitter important for lots of things. It is also used as a drug.
- role in central nervous system
- role in peripheral nervous system
- receptors and signaling
- role in disease
Role in Central Nervous System
Dopamine is an important neurotransmitter in the CNS. It is involved in the following systems:
- mesolimbic - appears to be involved in psychotic symptoms
- substantia nigra - control of voluntary movement
- ventral tegmental area - reward, drug addiction, schizophrenia
- released from hypothalamus, where it tonically inhibits prolactin secretion from the anterior pituitary
- mesocortical - may have effect on negative symptoms of psychosis
Role in the Peripheral Nervous System
- Dopamine is an important postganglionic sympathetic neurotransmitter acting primarily in renal vascular beds.
- It appears to induce vasodilation at lower doses but vasoconstriction at higher doses.
- It is also likely involved in modulating signals in some ganglia and the ENS.
- activates β1 receptors in the heart, increasing heart rate and contractility
Dopamine Receptors and Signaling
- All DA receptors in the brain are metabotropic, generally causing slow inhibitory action on CNS neurons.
- The D1 receptor is typically associated with adenylate cyclase stimulation and cAMP production, thought to lead to smooth muscle relaxation and vasodilation
- The D2 receptor is thought to inhibit adenylate cyclase, reducing calcium influx and opening potassium channels. It also also appears to inhibit NE release (after binding to pre-synaptic sites?)
Role in Disease
- Dopamine overactivity is associated with schizophrenia
- Loss of dopamine signaling is involved with Parkinson's disease
- Dopamine reward system is involved in most or all cases of drug addiction, with projections leaving the VTA and projecting to the nucleus accumbens.
D2 blockers can