Dopamine/dopaminergic system

Both amphetamine and cocaine have also been reported to support intracranial self-administration in the mesolimbic/mesocortical dopaminergic system. Rats will self-administer cocaine into the medial prefrontal cortex (Goeders and Smith 1983). while amphetamine is self-administered into the orbitofrontal cortex of rhesus monkeys (Phillips and Rolls 1981) and the nucleus accumbens of rats (Hoebel et al. 1983 Monaco et al. 1981). These data indicate that the mesolimbic/mesocortical dopaminergic system is involved in the initiation of stimulant reinforcement processes, and this work suggests that the region of the nucleus accumbens, more specifically the mesolimbic dopamine system, may be an important substrate for reinforcing properties of several psychomotor stimulant drugs. 

Dopamine is a catecholamine neurotransmitter in the CNS and at some ganglia in the autonomic nervous system. To date, three main types of receptors have been found D1( D2, and D3. The main dopaminergic systems in the brain are the nigro-neostriatal... 

Schizophrenia is a chronic, complex psychiatric disorder affecting approximately 1% of the population worldwide. The chronic nature of the illness, in addition to the early age of onset, results in direct and indirect health care expenditures in the U.S., which amount to approximately 30 to 64 billion dollars per year [4]. It is perhaps the most devastating of psychiatric disorders, with approximately 10% of patients committing suicide. The dopamine hypothesis of schizophrenia postulates that overactivity at dopaminergic synapses in the central nervous system (CNS), particularly the mesolimbic system, causes the psychotic symptoms (hallucinations and delusions) of schizophrenia. Roth and Meltzer [5] have provided a review of the literature and have concluded a role for serotonin as well in the pathophysiology and treatment of schizophrenia. The basic premise of their work stems from the known interaction between the serotonergic and dopaminergic systems. 

In early phases of PD, dopamine loss affects primarily the posterior putamen (the striatal motor area) but later spreads to involve other nigrostriatal regions. In later stages, more widespread dopamine loss and neuronal degeneration in non-dopaminergic systems, such as the locus coeruleus and the raphe nuclei may account for some of the non-motor aspects of PD. 

Altered dopaminergic system function has been implicated in major depression. Patients with major depression have been reported to have lower CSF levels of the dopamine metabolite homovanillic acid (HVA) compared to nondepressed controls, with more severely depressed patients having still lower CSF HVA levels (see [42] for a... 

The effects of developmental exposure of pyrethroids on the dopaminergic system, which is considered to be related to behavior, were examined in several studies, but inconsistent results were obtained. Administration of deltamethrin between gestation day 6 and 15 induced increase of DOPAC (dopamine metabolite) levels in adult rats [54]. Exposure of fenvalerate on gestation day 18 and during postnatal days 2-5 produced no effect on monoamine levels on postnatal day 21 [55]. Gestational and lactational exposure to fenvalerate decreased and increased 3H-spiroperidol binding in striatum after development, respectively, whereas only lactational exposure of cypermethrin induced increase in 3H-spiroperidol binding [56]. 

Bruxism mainly occurs in stage 2 sleep and REM sleep (Bader et ah, 1977). A relationship to stress and anxiety has been suggested, but the disorder can be chronic without apparent association with stress (Faulkner, 1990 Pierce et ah, 1995). It has been suggested that the central dopaminergic system may be involved in the modulation of sleep bruxism (Lobbezoo et al., 1997). Case reports indicate that bruxism can be induced by the SSRI paroxetine (Romanelli et al., 1996). The mechanism remains unclear possibilities include sleep disturbance, serotonergic-mediated inhibition of dopamine manifesting as akathisia, and SSRI-induced anxiety. SSRI-induced bruxism may respond to therapy with buspirone (Ellison et al., 1993). 

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