E.presynapticregulationa, receptors located on presynaptic nerve ending,thestimulation of the a, receptors causes feedbackinhibition of the release of norepinephrineConversely, low concentration of NA combines withpresynapticβ,receptor which may facilitate the releaseofNA
F.presynaptic regulation α2 receptors located on presynaptic nerve ending ,the stimulation of the α2 receptors causes feedback inhibition of the release of norepinephrine. Conversely, low concentration of NA combines with presynapticβ2 receptor which may facilitate the release of NA
G:postsynapticregulationDown-regulation.when the agonist is used long- term. it induces adecrease in the number or sensitive of its receptors.it is the reason that tachyphylaxis or tolerance to theeffects of somedrugs
Down -regulation: when the agonist is used long- term. it induces a decrease in the number or sensitive of its receptors. it is the reason that tachyphylaxis or tolerance to the effects of some drugs G: postsynaptic regulation
Up-regulation:when the antagonistis used long-termit inducesa increase in the number or sensitive ofitsreceptors.once the antagonistis stop using,theelevated numberofreceptors can produce anexaggerated response to low concentration of agonist
Up-regulation: when the antagonist is used long-term ,it induces a increase in the number or sensitive of its receptors.once the antagonist is stop using, the elevated number of receptors can produce an exaggerated response to low concentration of agonist
AdrenergicnerveagonistsL.Adrenoceptoragonista-receptoragonist(NA)a-receptoragonist (phenylephrinea-receptor agonist(clonidine)B-receptoragonist(isoprenaline,Adrβ,-receptoragonist(dobutamine)B-receptoragonist (salbutamol)2.Mimeticswithindirecteffectonadrenergicreceptor(ephedrine
1. Adrenoceptor agonist α-receptor agonist (NA) α1 -receptor agonist (phenylephrine) α2 -receptor agonist (clonidine) β-receptor agonist (isoprenaline,Adr) β1 -receptor agonist (dobutamine) β2 -receptor agonist (salbutamol) 2. Mimetics with indirect effect on adrenergic receptor (ephedrine) Adrenergic nerve agonists
Chemistry & pharmacokinetics of sympathomimeticdrugsthePhenylethylaminebeconsideredparentmayThisofthedrugs.compoundsympathomimeticwithringcompoundconsistsofabenzeneanethylamine side chain.The structure permitssubstitutions to be made(l)on theterminalamino group(2)on thebenzene ring(3)onthealphaorbetacarbons
Chemistry & pharmacokinetics of sympathomimetic drugs Phenylethylamine may be considered the parent compound of the sympathomimetic drugs. This compound consists of a benzene ring with an ethylamine side chain. The structure permits substitutions to be made (1)on the terminal amino group (2)on the benzene ring (3)on the alpha or beta carbons