Amphetamines dopamine receptors

The most consistent and potent antagonism of amphetamine effects on increased motor activity and stereotyped movements is obtained with antagonists at dopamine receptors of the D2 subtype (Creese et al. 1982). This is not the case with amphetamine s disruptive effects on social and aggressive behavior. So far, no antagonists have been identified that reverse amphetamine s disruption of sexual, play, maternal, or aggressive behavior. 

This benzylisoquinoline alkaloid inhibits in vitro the specific bonding of [3H] dopamine to dopamine receptors and abrogates amphetamine-induced circling behavior in rodents with unilateral degeneration of dopaminergic neurons in the corpus striatum (109). 

Altier, N., and Stewart, J., Dopamine receptor antagonists in the nucleus accumbens attenuate analgesia induced by ventral tegmental area substance P or morphine and by nucleus accumbens amphetamine, J. Pharmacol. Exp. Ther., 285, 208, 1998. 

Dopamine activity can be enhanced in one of four main ways. Medications can stimulate dopaminergic nerve cells to release dopamine into the synapse. This is the way that stimulants such as methylphenidate (Ritalin), dextroamphetamine (Dexe-drine), and dextroamphetamine/amphetamine (Adderall) work. In addition, certain drugs of abuse, notably cocaine and methamphetamine, act in part in this way. Providing more of the raw material that nerve cells use to manufacture dopamine can also increase dopamine activity. This is the approach that neurologists use when they prescribe L-DOPA (Sinemet) to patients with Parkinson s disease. Nerve cells convert L-DOPA into dopamine. L-DOPA otherwise has little place in the treatment of psychiatric disorders. Dopamine activity can also be increased by medications that directly stimulate dopamine receptors. Bromocriptine, another medication used to... 

FIGURE 2.9 Dopaminergic synapse. The release of dopamine (1) can be enhanced by compounds such as amphetamine and methylphen-idate (1). Once released, dopamine binds to two types of dopamine receptors. The family of D1 receptors includes the D1 and D5 receptor (2) and the family of D2 receptors includes the D2, D3, and D4 receptors (3). Dopamine is removed from the synapse via cleavage by catechol-O-methyl-transferase (COMT) or via reuptake by the dopamine transporter (4). 

There is also preliminary data that risperidone, an atypical antipsychotic that antagonizes multiple receptor types including dopamine receptors and serotonin receptors, may affect certain ERP components. A study of chronic risperidone delivery via subcutaneous implants reported increased P20 amplitude but no effects on the N40 component. Risperidone in this study was unable to block the amphetamine-induced decreases in the P20 component, but attenuated amphetamine-induced reduction of the N40 (Siegel et al., 2004). 

KEY WORDS Dopamine receptors behavior amphetamine striatum nucleus accumbens neuropeptide sprouting. 

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