Posted by Shawn. T. on February 13, 2003, at 22:52:44
In reply to dopamine receptors - ADD and BP, posted by cybercafe on February 9, 2003, at 23:44:05
There is some disagreement over whether ADHD involves a hypodopaminergic or hyperdopaminergic state; the evidence leans somewhat more towards hypo- in my opinion. In ADHD, dopamine is usually associated more strongly with hyperactivity than attention deficits. Based on available genetic evidence, D4 and D5 receptors may be involved in some types of ADHD (see http://www.neurotransmitter.net/adhdgenetic.html for verification). The D4 receptor gene has been associated with behaviorial components of ADHD but not with cognitive deficits. There is some evidence that D2 receptors may be involved in the response to Ritalin (see http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11730150&dopt=Abstract ). One can, however, argue that that study only shows that increased availability D2 receptors is associated with a better response to Ritalin; this is perhaps only a sign of hypodopaminergic traits rather than a sign that D2 receptors are directly involved in ADHD. There is some evidence showing that D3 receptors are involved in hyperactivity in rats, and there may be some evidence for D1 receptors although I didn't note any; there is no genetic evidence supporting these receptors, however.
Your question was about ADD; I'm assuming that you're asking about attention deficit rather than hyperactivity. In that case, you need to do more research into epinephrine and norepinephrine rather than dopamine. Hypernoradrenergic states are common to both ADHD (at least some types) and mania (almost all types). As far as which dopamine receptors may be involved in bipolar disorder, none of the genes encoding them have been associated with the disorder. Excessive activation of D1 receptors in mania is an interesting theory, but there is only a small body of evidence available to support that assumption ( http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1531387&dopt=Abstract and http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8775765&dopt=Abstract ). There is no evidence to show that D2 receptors are involved in mania or mood stabilization ( http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12359678&dopt=Abstract ). Hope that helps,
Shawn
poster:Shawn. T.
thread:140389
URL: http://www.dr-bob.org/babble/20030208/msgs/200254.html