University of South Florida
Schizophrenia is a severe form of mental illness classified in the DSM IV-TR as a Psychotic disorder. It is characterize by broad impairments in cognition that place limitations on recovery (Eack, 2012, p. 235). Antipsychotic drugs are the first line of treatment for Schizophrenic patients, but come with adverse side-effects and many patients are treatment-resistant (Tandon, Nasrallahb, & Keshavanc, 2010). Adjunct treatments that focus on cognition and coping with stress, along with the antipsychotics have shown to be more effective (Sungur, Soyguur, Guuner, Uustuun, Cetin, & Falloon, 2011). Dopamine is a phenethylamine naturally produced by the human body. In the brain, dopamine functions as a neurotransmitter, activating the five types of dopamine receptor - D1, D2, D3, D4 and D5, and their variants. Dopamine is produced in several areas of the brain, including the substantia nigra. Dopamine is also a neurohormone released by the hypothalamus. Its main function as a hormone is to inhibit the release of prolactin from the anterior lobe of the pituitary.
Antipsychotic treatment in Schizophrenia
Antipsychotic drugs are built around the theory that schizophrenia is caused by an overactive dopamine system (Gigante, Lafer, & Yatham, 2012). This theory comes from the observation that amphetamines, which stimulate dopamine receptors, induce a psychotic state similar to schizophrenic symptoms. Dopamine functions as a neurotransmitter, activating five different types of receptors, called D1, D2, D3 ,D4, and D5. Dopamine is produced in several areas in the brain, such as the substantia nigra and releases as a neurohormone by the hypothalamus. Dopamine's main function as a hormone is to inhibit the release of proalctin from the anterior lobe of the pituitary. Dopamine receptors are responsible for many neurological processes, including motivation, pleasure, memory, learning, fine motor control, and cognition. Other neurotransmitter systems show evidence that they aid in schizophrenic symptoms, such as the dysfunction of glutamate, serotonin, and GABA systems (Jafari, Fernandez-Enright, & Huang, 2012). The hyperactivity of dopamine receptors in the mesolimbic pathway is responsible for the positive symptoms of Schizophrenia and the hypo-activity of the prefontal dopamine neurons may contribute to the negative and cognitive symptoms of schizophrenia. Clinically effective antipsychotics reverse the locomotor stimulating effects of amphetamine by antagonizing the mesolimbic dopamine receptors (Matthew, David, James, & Kjell). These drugs that block the post synaptic D2 dopamine receptors are the general treatment for Schizophrenia and are divided into first generation antipsychotics and the newer, second generation antipsychotics First generation antipsychotics blocks the D2, muscarinic, cholinergic, histaminergic, and adregneric receptors. Second generation antipsychotics have a broader range of receptors, which antagonizes the central serotonin receptors and blocks a range of dopamine receptors more weakly (Gardner & Bostwick, 2012). Side Effects of Antipsychotic Drugs
Although the antagonizing the dopaminergic system is therapeutically beneficial, it causes an array of side effects, especially problems with motor functioning. There are different side effects between the two types of drugs, where first generation drugs causes extra-pyramidal effects, or more commonly known as motor problems, such as the inability to move or the inability to not move. Second generation drugs causes weight gain, dyslipidemia (abnormal amount of lipids in the blood), and glucose intolerance (Bateman, 2012, p. 105-6). This reason for this difference is because first generation antipsychotics heavily block D2 receptors and second generation antipsychotics weakly block...