Dopamine modulation effects

Waszezak, B.L., and Walters, J.R. Dopamine modulation of the effects of y-aminobutyric acid on substantia nigra pars reticulata neurons. Science 220 218-221, 1983. 

It has been suggested that modafinil increases wakefulness by activating ai noradrenergic receptors or hypothalamic cells that contain the peptide hypocre-tin [3], or that it may act by modulating the GABAergic tone that might lead to an increased dopamine release in the nucleus accumbens. On the other hand, modafinil does not have any effect in DAT knockout mice. 

Another theory for the action of stimulant diugs in ADHD involves effects on nonstiiatal monoamine systems. Frontal cortical dopamine, norepinephrine, and serotonin are clearly important in cognitive functioning and impulse control. These neurotransmitters directly modulate reward-related behaviors associated with the striatal dopamine system. Moreover, the amygdala may be pharmacologically influenced leading to enhanced... 

In experiments with mice and squirrel monkeys, we confirmed and extended the antagonism of amphetamine-induced motor hyperactivity by naltrexone at the same time, however, amphetamine s disruption of aggressive and social behavior was not reversed by naltrexone (Winslow and Miczek, in press). Specifically, in mice, the resident s attack and threat behavior toward an intruder was even further reduced by amphetamine after naltrexone pretreatment (figure 7). Squirrel monkeys that are dominant within their social group exhibit significantly lower levels of aggressive display toward other group members and initiate fewer social interactions after amphetamine treatment naltrexone did not block these effects. The interactive effects of amphetamine and naltrexone on locomotor behavior are consistent with the proposed modulation of dopamine-mediated functions by opioids however, the interaction between amphetamine and naltrexone on social behavior appears to involve a different mechanism. 

The main mechanism of action of caffeine occurs via the blockade of adenosine receptors in the CNS. Adenosine is an autacoid, which is involved in the modulation of behavior, oxygenation of cells, and dilatation of cerebral and coronary blood vessels and indirectly inhibits the release of dopamine. The blockade of adenosine receptors by caffeine increases the activity of dopamine, which is implicated in the effects of caffeine (91). The question that arises from this observation is to know whether or not adenosine antagonists hold potential for the treatment of Parkinsonism, and further study on the adenosine receptor antagonists from medicinal plants should be encouraged. A possible source for such agents could be the medicinal flora of Asia and the Pacific, among which is the family Sapindaceae. 

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