Cholinergic synapses yog qhov chaw uas ob lub neurons, lossis neuron thiab lub cell effector uas tau txais lub teeb liab, tuaj rau hauv kev sib cuag. Lub synapse muaj ob daim nyias nyias - lub presynaptic thiab postsynaptic, nrog rau cov synaptic cleft. Kev xa tawm ntawm cov hlab ntsha impulse yog ua los ntawm tus neeg nruab nrab, uas yog, cov khoom xa tawm. Qhov no tshwm sim los ntawm kev sib cuam tshuam ntawm tus receptor thiab tus neeg nruab nrab ntawm lub postsynaptic membrane. Qhov no yog lub luag haujlwm tseem ceeb ntawm cholinergic synapse.
Tus neeg nruab nrab thiab receptors
Hauv parasympathetic NS, tus neeg nruab nrab yog acetylcholine, cov receptors yog cholinergic receptors ntawm ob hom: H (nicotine) thiab M (muscarine). M-cholinomimetics, uas muaj ib hom kev ua ncaj ncees, tuaj yeem txhawb nqa receptors ntawm daim nyias nyias ntawm hom postsynaptic.
Qhov kev sib txuas ntawm acetylcholine yog ua nyob rau hauv cytoplasm ntawm neuronal cholinergic xaus. Nws yog tsim los ntawm choline, nrog rau acetyl coenzyme-A, uas muaj mitochondrial.keeb kwm. Synthesis tshwm sim nyob rau hauv qhov kev txiav txim ntawm cytoplasmic enzyme choline acetylase. Acetylcholine yog tso rau hauv synaptic vesicles. Txhua lub hlwv no tuaj yeem muaj txog li ntau txhiab acetylcholine molecules. Cov hlab ntsha impulse provokes tso tawm ntawm acetylcholine molecules rau hauv lub synaptic cleft. Tom qab ntawd, nws cuam tshuam nrog cholinergic receptors. Cov qauv ntawm cholinergic synapse yog qhov tshwj xeeb.
Kev tsim kho
Raws li cov ntaub ntawv uas biochemists muaj, cholinergic receptor ntawm neuromuscular synapse tuaj yeem suav nrog 5 protein subunits uas nyob ib puag ncig ion channel thiab dhau los ntawm tag nrho cov tuab ntawm daim nyias nyias, uas muaj lipids. Ib khub ntawm acetylcholine molecules cuam tshuam nrog ib khub ntawm α-subunits. Qhov no ua rau ion channel qhib thiab postsynaptic membrane kom depolarize.
Types of cholinergic synapses
Cholinoreceptors txawv hauv zos thiab kuj txawv txav rau cov teebmeem ntawm cov tshuaj pharmacological. Raws li qhov no, lawv paub qhov txawv:
- Mascarin-sensitive cholinergic receptors - lub npe hu ua M-cholinergic receptors. Muscarine yog ib qho alkaloid pom nyob rau hauv ntau cov nceb lom xws li yoov agaric.
- Nicotine-sensitive cholinergic receptors - lub npe hu ua H-cholinergic receptors. Nicotine yog ib qho alkaloid pom nyob rau hauv cov ntawv luam yeeb.
lawv qhov chaw
Thawj yog nyob rau hauv cov ntaub so ntswg postsynaptic ntawm cov hlwb ua ib feem ntawm cov khoom nruab nrog cev. Lawv nyob ntawm qhov kawgpostganglionic parasympathetic fibers. Tsis tas li ntawd, lawv kuj pom muaj nyob rau hauv cov hlwb neuronal ntawm lub autonomic ganglia thiab hauv cerebral cortex. Nws tau raug tsim los hais tias M-cholinergic receptors ntawm txawv localization yog heterogeneous, uas ua rau txawv rhiab heev ntawm cholinergic synapses rau cov tshuaj ntawm ib tug pharmacological xwm.
Views nyob ntawm qhov chaw
Biochemists paub qhov txawv ntawm ntau hom M-cholinergic receptors:
- Nyob hauv lub autonomic ganglia thiab hauv nruab nrab paj hlwb. Qhov peculiarity ntawm yav dhau los yog tias lawv nyob hauv cheeb tsam sab nraum cov synapses - M1-cholinergic receptors.
- Nyob hauv plawv. Ib txhia ntawm lawv pab txo qhov tso tawm ntawm acetylcholine - M2-cholinergic receptors.
- Nyob hauv cov leeg du thiab feem ntau ntawm cov qog endocrine - M3-cholinergic receptors.
- Nyob hauv plawv, nyob rau hauv cov phab ntsa ntawm pulmonary alveoli, nyob rau hauv lub hauv paus paj hlwb - M4-cholinergic receptors.
- Nyob rau hauv lub hauv nruab nrab lub paj hlwb, nyob rau hauv lub iris ntawm lub qhov muag, nyob rau hauv lub salivary qog, nyob rau hauv cov ntshav mononuclear - M5-cholinergic receptors.
Kev cuam tshuam ntawm cholinergic receptors
Feem ntau ntawm cov teebmeem ntawm cov tshuaj paub tshuaj uas cuam tshuam rau M-cholinergic receptors yog txuam nrog kev cuam tshuam ntawm cov tshuaj no thiab postsynaptic M2- thiab M3-cholinergic receptors.
Cia peb xav txog kev faib cov tshuaj uas txhawb nqa cholinergic synapses hauv qab no.
H-cholinergic receptors nyob rau hauv postsynaptic daim nyias nyias ntawm ganglion neurons ntawm qhov kawg ntawm txhua lub preganglionic fibers (nyob rau hauv parasympathetic thiab sympathetic.ganglia), hauv thaj chaw carotid sinus, hauv adrenal medulla, hauv neurohypophysis, hauv Renshaw hlwb, hauv cov leeg pob txha. Qhov rhiab heev ntawm ntau yam H-cholinergic receptors tsis zoo ib yam rau cov tshuaj. Piv txwv li, H-cholinergic receptors nyob rau hauv cov qauv ntawm autonomic ganglia (neutral-type receptors) txawv ntawm H-cholinergic receptors nyob rau hauv cov leeg pob txha (cov leeg nqaij receptors). Nws yog qhov tshwj xeeb ntawm lawv uas ua rau nws muaj peev xwm xaiv thaiv cov ganglia nrog cov tshuaj tshwj xeeb. Piv txwv li, cov tshuaj curarepod tuaj yeem thaiv cov kab mob neuromuscular.
Presynaptic cholinergic receptors thiab adrenoreceptors koom nrog kev tswj hwm ntawm kev tso tawm acetylcholine hauv synapses ntawm neuroeffector xwm. Excitation ntawm cov receptors yuav inhibit qhov tso tawm ntawm acetylcholine.
Acetylcholine cuam tshuam nrog H-cholinergic receptors thiab hloov pauv lawv cov kev sib haum xeeb, nce qib ntawm postsynaptic membrane permeability. Acetylcholine muaj cov nyhuv excitatory ntawm sodium ions, uas tom qab ntawd nkag mus rau hauv lub cell, thiab qhov no ua rau lub fact tias postsynaptic membrane depolarizes. Thaum xub thawj, ib lub zos synaptic muaj peev xwm tshwm sim, uas ncav cuag ib qho txiaj ntsig thiab pib cov txheej txheem ntawm kev tsim kom muaj peev xwm ua tau. Tom qab ntawd, lub zos excitation, uas yog txwv nyob rau hauv lub synaptic cheeb tsam, pib kis mus rau tag nrho cov cell membrane. Yog tias M-cholinergic receptor stimulation tshwm sim, ces tus xa xov thib ob thiab G-proteins ua lub luag haujlwm tseem ceeb hauv cov teeb liab kis.
Acetylcholine ua haujlwmnyob rau hauv ib lub sij hawm luv luv. Qhov no yog vim lub fact tias nws yog sai hydrolyzed los ntawm qhov kev txiav txim ntawm enzyme acetylcholinesterase. Choline, uas yog tsim thaum lub sij hawm hydrolysis ntawm acetylcholine, yuav raug ntes los ntawm presynaptic xaus nyob rau hauv ib nrab ntawm lub ntim thiab thauj mus rau lub cytoplasm ntawm lub cell rau tom ntej biosynthesis ntawm acetylcholine.
Cov tshuaj uas ua rau cholinergic synapses
Pharmacological thiab ntau yam tshuaj muaj peev xwm cuam tshuam rau ntau yam txheej txheem uas cuam tshuam nrog kev sib kis ntawm synaptic:
- txheej txheem ntawm kev sib txuas ntawm acetylcholine.
- Txoj kev tso tus neeg kho kom haum xeeb. Piv txwv li, carbacholin tuaj yeem txhim kho qhov tso tawm ntawm acetylcholine, thiab botulinum toxin tuaj yeem cuam tshuam kev tso tawm ntawm cov neurotransmitter.
- Cov txheej txheem ntawm kev sib cuam tshuam ntawm acetylcholine thiab cholinergic receptor.
- Hydrolysis ntawm acetylcholine ntawm enzymatic xwm.
- Cov txheej txheem ntawm kev ntes choline, tsim los ntawm hydrolysis ntawm acetylcholine, los ntawm presynaptic xaus. Piv txwv li, hemicolinium muaj peev xwm inhibit neuronal uptake thiab thauj choline mus rau hauv lub cell cytoplasm.
Kev faib tawm
txhais tau tias txhawb nqa cholinergic synapses tuaj yeem tsis tsuas yog cov nyhuv no, tab sis kuj muaj cov nyhuv anticholinergic (kev nyuaj siab). Raws li lub hauv paus rau kev faib tawm ntawm cov tshuaj no, biochemists siv cov kev coj ua ntawm cov tshuaj no ntawm ntau yam cholinergic receptors. Yog ibua raws li txoj cai no, ces cov tshuaj uas cuam tshuam rau cholinergic receptors tuaj yeem raug cais raws li hauv qab no:
- Cov tshuaj uas cuam tshuam rau M-cholinergic receptors thiab H-cholinergic receptors: cholinomimetics suav nrog acetylcholine thiab carbachol, thiab anticholinergics - cyclodol.
- Txhais tau tias muaj anticholinesterase xwm. Cov no suav nrog physostigmine salicylate, prozerin, galanthamine hydrobromide, armine.
- Cov tshuaj uas cuam tshuam rau cholinergic synapses. Cholinomimetics suav nrog pilocarpine hydrochloride thiab aceclidine, anticholinergics suav nrog atropine sulfate, matatsin, platyfillin hydrotartrate, ipratropium bromide, scopalamine hydrobromide.
- Cov tshuaj uas cuam tshuam rau H-cholinergic receptors. Cholinomimetics suav nrog cytiton thiab lobelin hydrochloride. N-cholinergic blockers tuaj yeem muab faib ua ob pawg. Thawj yog ganglion-blocking agents. Cov no suav nrog benzohexonium, gigronium, pentamin, arfonad, pyrilene. Cov pab pawg thib ob suav nrog cov khoom zoo li curare. Cov no muaj xws li peripheral leeg relaxants xws li tubocurarine chloride, pancuronium bromide, pipecuronium bromide.
Peb tau saib kom meej ntawm cov tshuaj uas cuam tshuam rau cholinergic synapses.
