Drugs & Neurotransmitters. At a substrate level ~ Tryptophan increases serotonin substrate potentiation of other serotonergic meds Nerve condution ~ Role ions; Ca ++ & ?Mg + to stabilise ? One site of Li action subsequent reduced neurotransmitter release Presynoptic Autoreceptors
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potentiation of other serotonergic meds
MAO B (NA, DA) seleziline
Chronic exposure to high and low concentrations of neurotransmitters (or any substance acting as a receptor) will result in adaptation. Too much for a long time makes the receptors less sensitive and vice versa. The mechanism for this varies; receptor number, receptor shape, and second messenger systems all involved.
on the presynoptic neorone when stimulated provide negative feedback to reduce release of neurotransmitters
If a compound binds to a receptor, it will have some effect.
“Full” agonist when bound to a receptor, will turn it on fully.
Partial agonist when bound will only partially stimulate the effects. Thus, no matter how much you give, maximal effect (as compared to full agonist) won’t happen.
Antagonist binds to a receptor and doesn’t turn it on. Because its occupying the site, no one else (even the usual neurotransmitter) can’t get on. Reduced effect.
Probably some agents work here. Lithium appears to reduce the second messenger response to catecholamines; it reduces the response to TSH & ADH. Thus, the receptors are there in normal numbers; but nothing happens. This system can also be increased eg. Theophylline phosphodiesterase inhibition
Mode of action
1. Inhibition of reuptake of neurotransmitter amines increases the amount in synaptic cleft, increasing transmission. Delay in onset of action due to part synaptic adaptation.
2. Presynoptic autoreceptors stimulated by excess serotonin. Initial reduction in serotonergic transmission, less serotonin in synoptic cleft and subsequent autoreceptor down regulation. Eventually neurone adapts to increase serotonergic transmission and not be inhibited by normal concentrations of serotonin.
Reverse of neurolepts : more is less and less is more.