mine and norepinephrine. Dopamine is thought to play a role in memory formation and the onset of addictive behaviors, while norepinephrine has been linked with arousal and attentiveness.
Berridge notes that scientists have learned little about how ADHD drugs work because past studies have primarily examined the effects of the medicines at high doses. High-dose stimulants can cause dramatic spikes in neurotransmitter levels in the brain, which can in turn impair attention and heighten the risk of developing addiction.
'It is surprising that no one was looking at low-dose [ADHD] drugs because we know that the drugs are most effective only at low doses,' says Berridge. 'So we asked the natural question: what are these drugs doing at clinically relevant doses?'
To answer that question, Berridge and his team monitored neurotransmitter levels in three different brain regions thought to be targeted by ADHD drugs: the PFC and two smaller brain areas known as the accumbens which has been linked with processing 'rewards,' and the medial septum, which has been implicated in arousal and movement.
Working with rats, the researchers conducted laboratory and behavioral tests to ensure that animal drug doses were functionally equivalent to doses prescribed in humans. Then, using a type of brain probe - a process known as microdialysis - the UW-Madison team measured concentrations of dopamine and norepinephrine in the three different brain areas, both in the presence and absence of low-dose ADHD stimulants.
Under the influence of ADHD drugs, dopamine and norepinephrine levels increased in the rats' PFC. Levels in the accumbens and medial septum, however, remained much the same, the scientists found.
'Our work provides pretty important information on the importance of targeting the PFC when treating ADHD,' says Berridge, 'In particular it tells us that if we want to produce new ADHD drugs, we need to target [neurotransmitPage: 1 2 3 Related medicine news :1
. New Way to "See" Genes, Evaluate Effectiveness of Gene Therapies Discovered
. Inhaled Steroids Safe & Effective for Children with Asthma3
. Acupuncture May Help Chemotherapy Side Effects4
. ZD1839 Proves Effective - A Breakthrough in fighting Lung Cancer5
. Fluoride Found Effective in Osteoporosis 6
. Aspirin and Warfarin Are Equally Effective for Stroke Prevention 7
. Implantable Contact Lens Found Safe and Effective8
. Effective And Economical Agent For Anthrax9
. Stem Cell Transplants May Be Effective For MS Patients10
. Chemotherapy Pill Has Fewer Side Effects Than IV
. Effect of Osteosarcoma predicted by scans