Posted by Shawn. T. on June 29, 2004, at 20:31:06
In reply to Re: why are benzo's considered superior?, posted by 1980Monroe on June 28, 2004, at 21:41:22
Several barbiturates inhibit calcium channels; however, I don't know of any that cause them to open. GABA-A receptors modulate chloride channels; these are the channels that barbiturates and benzodiazepines affect. Both drug types attach to different binding sites on GABA-A receptors, which causes the receptors to exhibit a stronger affinity for GABA. Unlike benzodiazepines, barbiturates possess the ability (at higher concentrations) to cause chloride channels in GABA-A receptor complexes to open in the absence of GABA. These channels exhibit at least three different open states which last a varying number of milliseconds. Barbiturates increase the relative frequency of the occurrence of the longest open state and decrease the frequency of the occurrence of the shorter open states (see http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2482885 ). On the other hand, benzodiazepines only increase the frequency that the channels will open into the shortest open state (see http://www.acnp.org/g4/GN401000173/CH169.html ). Also, many barbiturates inhibit nicotinic acetylcholine receptors. Some benzodiazepines affect different targets as well. I've never heard that barbiturates bind to the inside of GABA-A receptor complexes. I don't think that it is accurate to state that barbiturates can act as GABA at high doses; they bind to different locations on the GABA-A receptor and therefore do not elicit the same effects.
Shawn
poster:Shawn. T.
thread:361064
URL: http://www.dr-bob.org/babble/20040627/msgs/361787.html