Posted by linkadge on July 12, 2007, at 9:46:44
In reply to Re: Ketamine » deniseuk190466, posted by FredPotter on July 11, 2007, at 20:41:44
Not sure what to say. I definately think there need to be more studies conducted. Ketamine might posess additional activities that give it its antidepressant effect.
Its also too early to throw out monoaminergic theories / neurotrophic theories on depression based upon this.
I still don't see solid proof that it is truely an antidepressant effect and not just a drug induced temprorary improvement. A lot of illegal drugs can improve depression very rapidly.
Growth factors, BDNF, NT-3 etc, when injected directly into the brain, can produce rapid antidepressant effects that last as long as two weeks. In such cases, it is impossable to separate the antidepressant effect from the induction of growth of new brain cells, as the grwoth factor seems to induce both at the same time. BDNF for instance, increases the sensitivity of the d3 receptors in reward areas of the brain, in addition to growing new brain cells. So it may not be the question of whether lack of new brain cells cause depression, or depression causes lack of new brain cells. It could be that the brain lacks substances that posess both mood elevating and neurotrophic effects.
It is possable that Ketamine is producing a rapid increase in trophic factors, which is possable since some other NMDA antagonists have a similar ability to produce rapid elevations of such substances.
Zinc, for intance, produces a rapid antidepressant effect in mouse swim tests, it also produces a rapid increase in BDNF.
Although, I don't know what kind of effect long term administration of such substances would have on the depressive state.
The problem with saying that the neurotrophic model is bunk is that there would still be real differences in the brains of the depressed patient. Hippocampal volumes would still remain atrophied etc.
I personally think without any induction of new brain cells, that this antidepressant response could "kick out" as rapidly as it kicks in.
The plight of depression has been continually riddled with fast acting depression cures, so I think that follow up studies are neccesary to determine the nature of the effect.
Linkadge
poster:linkadge
thread:768826
URL: http://www.dr-bob.org/babble/20070710/msgs/769138.html