Dopamine plays critical role in the modulation of sleep, wake, and arousal states

Methamphetamine, the drug of choice for long-distance truckers and college students pulling all-nighters, appears to do a similar trick for fruit flies, too. This finding is one of several in a new study that demonstrates a critical role for the neurotransmitter dopamine in the modulation of sleep, wake, and arousal states.

The work is reported by Dr. Ralph Greenspan and colleagues at The Neurosciences Institute in San Diego.

The researchers found that long, sleepless nights, heightened locomotor activity, frenetic brain activity, and frenzied (but ultimately ineffective) courtship behavior are all characteristics of fruit flies on methamphetamine, the effects of which are known to act through the neurotransmitter dopamine.

In the new work, the researchers showed that genetically engineered flies whose dopamine cells could be turned off experimentally, or flies that have received dopamine inhibitors, show converse behavioral effects to those seen in normal flies that have ingested methamphetamine.

The results suggest that the right balance of dopamine is necessary for proper brain functioning, as has been seen in human studies of attention and distraction. Dopamine has been implicated in numerous aspects of brain function in humans and other animals, and many of these brain functions involve the modulation of neuronal activity and the ability to assign proper saliency (or relevance) to sensory stimuli.