Dopamine agonists Neuroleptics

Geriatric Considerations - Summary Pramipexole is a nonergot dopamine agonist that directly stimulates dopamine Dj receptors. It can be used in combination wit h le-vodopa or as monotherapy. If discontinued, pramipexole should be slowly tapered because abrupt discontinuation can cause confusion, hallucinations, and a condition similar to neuroleptic malignant syndrome. 

The hypothetical link between dopamine and schizophrenia was forged by two reciprocally related findings. The first was that potent dopamine agonist stimulants like d-amphetamine and cocaine could cause a psychosis that was schizophrenia-like, in that it had auditory hallucinations and paranoia. The second was that the neuroleptic drugs that were effective in reversing both schizophrenia and stimulant-induced psychosis were dopamine blockers. Moreover, the antipsychotic potency of the neuroleptics was proportional to their binding affinity to the D2 receptor. 

Dopamine - low doses of the dopamine agonist apomorphine increase slow-wave sleep and, like other dopaminometics, cause somnolence in patients with Parkinson s disease. Conversely, dopamine autoreceptor antagonists, which enhance dopamine release, reduce both REM and non-REM sleep. Stimulants such as cocaine cause arousal by activating D2 postsynaptic receptors, effects which are blocked by most neuroleptics. 

Dopamine agonists produce a decrease of brain DOPAC and HVA concentrations, which can be antagonized by neuroleptic drugs (107, 108). ... 

For CNS aspects of dopamine, agonists and antagonists see Neuroleptics, Parkinsonism. 

Additive dopaminergic effects would be expected. The serotonin syndrome is thought to occur because of increased stimulation of the 5-HT receptors in the brainstem and spinal cord. A syndrome resembling neuroleptic malignant syndrome (which has similar symptoms to the serotonin syndrome) can occur when a dopamine agonist like bromocriptine is... 

Medication Recent (past 72h) exposure to dopamine antagonist or withdrawal of dopamine agonist Serotonergic addition /T coinciding tenporally with synptoms Neuroleptic not recently added or increased May have been non-concordant with antipsychotics... 

In Kaiser C, Kebabian JW (eds) Dopamine receptors. Am Chem Soc Washington, pp 175-196 Tamminga C, Gotts MD, Miller MR (1983) Dopamine agonist treatment of schizophrenia and neuroleptic-associated dyskinesias. Acta Pharm Suec Suppl 2 153-158... 

Figure 7.8 Dopamine and motor function. When nigrostriatal dopamine activity is normal so is motor function. Any reduction in this DA activity, as in Parkinson s disease, results in reduced motor activity, i.e. akinesia. By contrast, too much DA activity, as in Huntington s Chorea, produces abnormal motor function, i.e. dyskinesia. The latter may be controlled by neuroleptic drugs (DA antagonists) but they can swing the balance in DA activity sufficiently to produce akinesia (Parkinsonism). DA agonists (and levodopa) may overcome akinesia but can induce DA overactivity and dyskinesia (peak dose effect) (see Chapter 15)...

Dopamine A few studies have examined the dopaminergic effects of LSD. The affinity of LSD for D2 receptors is similar to its affinity for 5-HT2 sites, and it has a slightly lower affininty for D1 receptors (Watts et al. 1995). LSD has partial agonist effects at D2 receptors as seen in the inhibition of prolactin release (Giacomelli et al. 1998). Neuroleptic drugs are also used clinically to terminate an LSD experience. Thus, the effects of LSD on dopaminergic function may contribute to its hallucinogeinc effects. 

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