For 10 points, name this hormone, a reduction of which can cause Parkinson's disease.
The lack of fragile X mental retardation protein alters the relay of messages in this molecule's namesake pathway. Prolactin counteracts the effect of this molecule, which can be responsible for sexual arousal and pleasure, and one hypothesis regarding schizophrenia states that psychotic episodes are triggered specifically by the activation of its receptors. For 10 points, name this hormone, a reduction of which can cause Parkinson's disease.
The lack of fragile X mental retardation protein alters the relay of messages in this molecule's namesake pathway.
{dopamine}