Similar overall effect, but how do they differ?

Caffeine, Amphetamines, Cocaine, Methamphetamines, Methylphenidate, etc are all stimulants though to different degrees. Can someone explain how they differ from one another in terms of function and what area(s) of the brain each largely effects?

One Response to “Similar overall effect, but how do they differ?”

  1. Ashley Says:

    I cant tell you about all of them, but I hope this helps:

    Caffeine is a PDE (phosphodiesterase) inhibitor. It inhibits the breakdown of cAMP (cyclic adenosine monophosphate). This means that cAMP levels in myocardial and smooth muscle cells are increase (ie, because cAMP is not broken down). cAMP opens Na+ and Ca2+ channels in these cells. Na+ in the cells means that action potentials in the SA (sinoatrial) node are reached earlier, and so heart rate increases. Also, Ca2+ influx is prolonged, which prolonges the action potential plateau of cariac muscle cells, and so contractility (force of heart beat) is increased. Lastly, the opening of Na+ channels in smooth muscle cells means that smooth muscle cells contract (ie action potentials in cells are created quicker) and so blood vessels (specifically arteries and arteriols) are thinner, and this increases blood pressure.

    I am sure with a bit of 'internetting' you can find stuff like this for the other ones.

    Caffeine, by the way, is a methylxanthine, which is basically another name for a PDE inhibitor.

    Hope this helps

    Ashley

    EDIT:
    I did some research for you, aren't I nice!
    Amphetamines increase intracellular levels of epinethrine and norepinethrine. These will, therefore, bind to adrenoreceptors, which will cause vasoconstriction (alpha-1 receptors, rising blood pressure), increase heart rate (beta-1 receptors) and contractility (beta-1 aswell), bronchodilation (beta-2 receptors, means you can breath easier) and will cause smooth muscle relaxation of the glands, intestines and stuff, so you dont need the toilet! (alpha-1 receptors).

    Cocaine will cause vasoconstriction AND still block Na+ channels, so I am not sure about this one. It also has complecated brain-related effects, which I dont know about.

    Methamphetamines will cause epinephrine (and epinethrine related products) to be released into the blood, and also to accumulate on the post syaptic cleft. This will, therefore, do everything that amphetamines will do – the 'meth' bit means a methyl (CH3) group has been added to the drug, this allows it to cross the blood-brain barrier, and therefore have more brain-related effects, which, like I said, I dont really know about.

    Methylphenidate is apparently a norepinethrine and dopamine transporter, and therefore, again, will do everything amphetamines do (increase heart rate, contractility, vasoconstriction, etc).

    Well, hope that answers your q

    Ashley