Primer on the workings of cognition-affecting chemicals
May 27, 2012 9:33 AM Subscribe
Neuropharmacologyfilter. Brief me on the practical basics (and the theoretical rudiments) of what it means to have a chemical in one's "system."
posted by foursentences to science & nature (5 answers total) 7 users marked this as a favorite
In particular here I'm interested in cognition-affecting chemicals, rather than more bodily drugs like, say, poisons or painkillers. (I understand, at least reductively, how a chemical could affect non-brain functions -- dilates the blood vessel, accumulates in the liver, causes a muscle to fire, etc. Much more mysterious to me are the workings of chemicals that interact with the mind.)
- What is one's "system"? First, when we speak of "having a (cognition-affecting) drug in your system", what are we referring to? Just your bloodstream (plus the brain and the various filtration organs that abut it)?
.......> Does every chemical that affects one's cognition/mood/psychology do so by interacting directly with neurons?
- Duration. Suppose that if I ingest n amount of a chemical, it will take exactly 4 hours before I am again functioning as though I had never taken any. What happens if I ingest 2n amount of the same chemical?
.......> Will it take 8 hours before I am functioning normally? 4 hours? Somewhere in between? Why?
.......> Does it depend on the chemical? If so, what if the chemical is caffeine?
- Intensity. Are there practical "ceilings" on the intensity with which a given chemical can affect a person at a given time?
.......> The mechanism I imagine for this would be: if you take n amount of cocaine then 33% of your receptors will bind with it; if you take 2n amount then 67% of your receptors will bind with it; if you take 3n amount then 100% of your receptors will bind with it; but if you take 4n amount then still only 100% of your receptors can bind with it. Is this a correct understanding?
.......> If so, what happens to the extraneous n amount? Does it get filtered out of one's "system" and go to waste, or does it linger until receptors are again available, effectively prolonging the high?
.......> In what ways, and for what reasons, do the answers to these questions depend on the chemical?
- Latency. Why do some drugs (e.g., recreational drugs) produce an instantaneous but relatively short-lived effect, while others have no immediate impact but affect cognition for days (e.g., SSRI's)?
- Why does a high end? If your mind is affected because molecules of the drug are chemically binding with the receptor cells in your brain -- why don't the molecules just continue to stick to those receptors forever (or at least until some even more receptive chemical comes along to stick to them instead)? Are the molecules of the drug somehow being metabolized or broken-down by the receptors? Are the receptors themselves being replaced or recycled?