Could Someone Break Down the Whole Receptor/ Blocker/ Agonist/ Antagonist Thing Please?
Question by Gnochon: Could someone break down the whole receptor/ blocker/ agonist/ antagonist thing please?
I think I understand sympathetic (adrenergic) parasympathetic (muscarinic) and enteric; I understand axons, myelin sheaths, dendrites, neurotransmitters, carrier proteines, I know about the synaptic cleft, reuptake of neurotransmitters… but that’s about it. Please elaborate on this: alpha blockers match up to “alpha receptors”? – or are there no such thing? Are there just a bunch of receptors sticking out and betas or deltas or alphas make a run for any ol’ receptor, blindly? Surely there has to be a match? If there is a match, is it beta agonist or beta blocker to beta receptor? Alpha agonist or alpha blocker to alpha receptor? Is that how that works? Actually that’s pretty much my question right there. And also: all these neurotransmitters (assuming these alphas betas and deltas are exactly that – “neurotransmitters”?) all these neurotransmitters are… what – enzymes? Thanks a lot guys – mid-term tonight! Oy!
Best answer:
Answer by Peter H
I have never come across this particular worry before, but there you go. Perhaps the best way to resolve it is to state that “alpha blocker” is actually shorthand for “alpha receptor blocker” so without an alpha receptor there can be no alpha blocker. A practical problem is that not all drugs are specific in their agonist or antagonist action. Adrenaline (epinephrine) is a good example, having effects on both alpha and beta receptors. Noradrenaline, often spoken of as a specific alpha agonist, also has beta effects. Even the beta receptors are not homogenous, Beta-1 receptors are found in the heart and increase rate and force of contraction, beta-2 receptors in the smooth muscle of the airways and dilate the airways. Isoprenaline, an old drug, was a non-specific beta agonist and had both effects. Salbutamol is much more specific for beta-2, but can still cause tachycardia.
I won’t even begin with all the opiate receptors. Suffice it to say that new subgroups of receptors continue to be discovered, based on analysis of the effects of different agonists and antagonists.
No, neurotransmitters are not enzymes. Their molecular structures key to the receptors, allowing associated channels in the cell wall to open
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