Cholinergic Agonists PDF

CHOLINERGIC AGONISTS  Cholinergic agonists (cholinomimetic agents) are a large group of drugs that mimic the actions of ACh which includes: OVERVIEW Ach-R stimulants Cholinesterase inhibitors Ach-R stimulants are further...

CHOLINERGIC AGONISTS  Cholinergic agonists (cholinomimetic agents) are a large group of drugs that mimic the actions of ACh which includes: OVERVIEW Ach-R stimulants Cholinesterase inhibitors Ach-R stimulants are further classified according to the type of receptors they selectively stimulate: Muscarinic cholinomimetics Nicotinic cholinomimetics They are sometimes classified according to their mechanism of actions, i.e.: Direct acting (binding directly to the ACh-R) cholinergic agonists Indirect acting (inhibit the hydrolysis of endogenous ACh) cholinergic agonists  In the ANS, ACh is a neurotransmitter at the autonomic ganglia (both parasympathetic and sympathetic) preganglionic fibers terminating in the adrenal medulla postganglionic fibers of the parasympathetic division THE In addition, cholinergic neurons innervate the muscles CHOLINERGIC of the somatic system NEURON *Patients with Alzheimer’s disease have a significant loss of cholinergic neurons in the temporal lobe and cortex. It is a progressive neurodegenerative disorder in the form of dementia occurring in the middle age & later. Most of the drugs available to treat the disease at this stage are acetylcholinesterase (AChE) inhibitors  NEUROTRANSMISSION AT THE CHOLINERGIC NEURON Neurotransmission in cholinergic neurons involves six steps including: (1) synthesis (2) storage (3) release (4) binding of Ach to a receptor (5) degradation of the NT in the synaptic gap (6) the recycling of choline  Choline acetyltransferase 8 8  SYNTHESIS OF ACH Choline is transported from the plasma into the neuron by a specialised carrier system referred to as the high-affinity choline transporter (Na + dependent) Choline is more polar (i.e. has a quaternary nitrogen -NCH 3+) & cannot diffuse through the membrane. The uptake of choline is the rate-limiting step in acetylcholine synthesis ( *This carrier system can be inhibited by the drug hemicholinium) Choline acetyltransferase catalyses the reaction of choline with acetyl CoA to form acetylcholine in the cytosol  STORAGE OF ACH The mature vesicle ACh is packaged into also contains vesicles called adenosine vesiculin by an active triphosphate (ATP), transport process. ions(Ca2+ & Mg2+) and proteoglycan  RELEASE OF ACH An action potential stimulates voltage-sensitive Ca2+ channels in the presynaptic membrane Elevated Ca2+ levels promote the fusion of synaptic vesicles with the cell membrane and release of their contents into the synaptic cleft. *This release can be blocked by botulinum toxin (a nerve toxin produced by the bacterium Clostridium botulinum) In contrary black widow spider venom causes all the ACh stores in synaptic vesicles to empty into the synaptic gap  BINDING TO A RECEPTOR Released ACh diffuses across the synaptic Presynaptic (auto-) space and binds to receptors in the Binding to a receptor either two types of membrane of the leads to a biological postsynaptic receptors neuron that released response within the cell (M & N) on the target ACh cell  DEGRADATION The signal at the postsynaptic effector site is rapidly terminated, because acetylcholinesterase (AchE) cleaves ACh to choline and acetate in the synaptic cleft  RECYCLING OF CHOLINE Choline may be recaptured by a Na+-coupled, high-affinity choline uptake system and transported back into the neuron for further ACh synthesis  CHOLINERGIC RECEPTORS (CHOLINORECEPTORS) (1) Muscarinic cholinergic receptors M receptors are 7 transmembrane protein that are coupled to a G-protein (GPCRs) G-protein functions as a transducer (a device capable of converting one form of signal to another) These receptors bind to both ACh and muscarine – but only a weak affinity for nicotine 5 subclasses of M receptors have been distinguished: M 1-5: M1, M3, and M5 lead to cellular excitation, whereas M2 and M4 inhibit cellular excitability  LOCATION OF M-RECEPTORS All five subtypes have been found on neurons M1 receptors are also found on gastric parietal cells (where they control gastric acid secretion) M2 receptors on cardiac cells and smooth muscle (slow the heart rate & force of contraction) M3 receptors on the bladder, exocrine glands, and smooth muscle  ACH SIGNAL TRANSDUCTION MECHANISMS M1 & M3 receptor transduction mechanisms: When the M1 or M3 receptors are activated, they undergo a conformational change and interacts with a G protein, designated Gq, which in turn activates phospholipase C This leads to the hydrolysis of phoshatidylinositol-(4,5)-bisphosphate (PIP 2) to yield diacylglycerol (DAG) and inositol (1,4,5)- trisphosphate (IP3) IP3 cause an increase in intracellular Ca2+ from intracellular stores, sarcoplasmic reticulum) Ca2+ can then interact to stimulate or inhibit enzymes, or cause hyperpolarization, secretion, or contraction  ACH SIGNAL TRANSDUCTION MECHANISMS M2 & M4 cholinergic receptor transduction mechanisms in cardiac cells In contrast, activation of the M2 subtype on the myocardium muscle stimulates a G protein, designated Gi This activity then inhibits adenylyl cyclase (AC) activity – which normally catalyzes the conversion of ATP to cAMP (second messenger) The resultant effect of such an inhibition is an increased K+ conductance to which the heart responds with a decrease in rate and force of contraction  ACH SIGNAL TRANSDUCTION MECHANISMS Nicotinic cholinergic receptors (N) These receptors bind to both ACh & nicotine – and also show only a weak affinity for muscarine The N cholinergic receptor is composed of five polypeptides transmembrane subunits, and functions as a ligand-gated ion channel Binding elicits a conformational change that allows the entry of Na+, resulting in the depolarization of the effector cell (excitatory post-synaptic potential; EPSP). Nicotine (or ACh) initially stimulates and then blocks the receptor (due to receptor desensitisation) following persistent stimulation  NICOTINIC RECEPTORS Nicotinic receptors are located in the CNS adrenal medulla all autonomic ganglia neuromuscular junction of sympathetic and somatic nervous system Those at the neuromuscular junction are designated NM, while those in the postganglionic cell body & dendrites are designated NN *NN receptors are selectively blocked by hexamethonium, whereas NM receptors are specifically blocked by tubocurarine.  DIRECT-ACTING MUSCARINIC CHOLINERGIC AGONISTS This group of drugs mimic the effects of ACh by binding directly to muscarinic cholinergic receptors. These agents are classified as either: synthetic esters of choline, such as carbachol , methacholine, carbamic acid and bethanechol naturally occurring alkaloids, such as pilocarpine, muscarine, & nicotine All have longer durations of action than Ach They show little specificity or selectivity for the various subtypes of M receptors in their actions, which limits their clinical usefulness Some of these agents stimulate both the N & M cholinergic receptors  PHARMACOKINETICS Synthetic esters of choline are poorly absorbed (from the GIT) & poorly distributed into the CNS because they are hydrophilic - as a result they are less active by oral route They are inactivated in the GIT. They are mostly reserved for ophthalmic application – due to their potential toxic effects They differ in their susceptibility to hydrolysis by AChE (acetylcholinesterase) Metacholine is more resistant to AChE – has a longer duration of action The b-methyl group (methacholine & bethanecol) reduced the potency of these drugs for N cholinergic receptors The natural cholinomimetic alkaloids (pilocarpine, nicotine) are well absorbed from most sites of administration Nicotine – lipid soluble liquid can also be absorbed across the skin. Muscarine – incompletely absorbed from the GIT, but may be too toxic when ingested. Pilocarpine – moderately lipophilic and well absorbed from the GIT; also enters the CNS (crosses the BBB) They are excreted mainly by the kidneys; acidification of the urine enhances the clearance of these tertiary amines (because at acidic pH, they are ionised and more water soluble)  ACETYLCHOLINE ACh is a quaternary ammonium compound that cannot penetrate membranes It is the NT of parasympathetic and somatic nerves as well as ganglia *It is therapeutically of no importance because of its multiplicity of actions, and its rapid inactivation by both the membrane AChE & plasma butyrylcholinesterase (BuChE; pseudocholinesterases) ACh has both M and N cholinergic activity  PHARMACOLOGICAL PROPERTIES OF ACH ACh is rarely given systemically because of its short t1/2 and its diffuse actions ACh has several primary effects on the cardiovascular system, i.e. Decreased heart rate and cardiac output Decrease in blood pressure Decreased strength of contraction (negative inotropic effect)  PHARMACOLOGICAL PROPERTIES OF ACH Decreased heart rate and cardiac output ACh, if injected IV, produces a brief decrease in cardiac rate and stroke volume resulting from interaction with the M2 receptors at the sinoatrial (SA) node of the heart ACh slows the heart rate by: decreasing the rate of spontaneous diastolic (time between ventricular contractions (systole), at which ventricular filling occurs) depolarization (the pacemaker current) and by increasing the repolarizing K+ current at the SA node The resultant effect is the delayed cardiac cycle due to the elevated threshold potential.  PHARMACOLOGICAL PROPERTIES OF ACH Decrease in blood pressure: Injection of ACh causes vasodilatation and lowers of BP The parasympathetic division does not innervate the vasculature but there are cholinergic receptors on the blood vessels (especially the M3 cholinergic receptors) The M receptors responsible for relaxation are located on the endothelial cells of the vasculature. Stimulation of these receptors activates the Gq-PLC-IP3 of the endothelial cells leading to Ca2+-calmodulin-dependent activation of endothelial NO synthase (eNOS) and production of NO (endothelium-derived relaxing factor; EDRF) NO also diffuses to adjacent smooth muscle cells and cause them to relax by catalyzing the conversion of GTP to cGMP (mediator responsible for the relaxation). *Atropine blocks these muscarinic receptors and prevents ACh from producing vasodilation  PHARMACOLOGICAL PROPERTIES OF ACH Decreased strength of contraction (negative inotropic effect) In the atrial muscles, ACh decreases the force of contraction both directly & indirectly Indirectly – as a result of decreasing cAMP and Ca 2+ channel activity at lower concentrations. Directly – at higher concentrations of ACh, there is inhibition of the M 2 cholinergic receptors resulting in receptor-mediated activation of G protein regulated K + channels; the cells are then hyperpolarised by the K+ influx – the ultimate response is reduced impulse generation and conduction This decrease in conduction is responsible for the complete heart block observed when large quantities of cholinergic agonists are administered BETHANECHOL It is structurally related to ACh but the acetate is replaced by carbamate and the choline methylated These structural changes renders it resistant to hydrolysis by AChE but not to all other esterases like BuChE The b-methyl group reduces the potency of bethanechol to N cholinergic receptors (selective for M cholinergic receptors) It has a duration of action of about 1 hour  BETHANECHOL Actions Bethanechol directly stimulates muscarinic receptors (M 3) causing increased intestinal motility and tone. It also stimulates the detrusor muscles of the bladder while the trigone and sphincter are relaxed, causing expulsion of urine (M3). Therapeutic applications In urologic treatment, bethanechol is used to stimulate the atonic (nonemptying) bladder, particularly in postpartum or postoperative, nonobstructive urinary retention. Oral bethanechol is useful in certain cases of postoperative abdominal distention (expansion) & gastric atony (lack of tone) or gasreparesis (delayed stomach emptying). Adverse effects Bethanechol causes the effects of generalized cholinergic stimulation including sweating, salivation, flushing, hypotension, nausea, abdominal pain, diarrhea, and bronchospasm. CARBACHOL Carbachol has both M as well as N actions (not selective) Like bethanechol, carbachol is an ester of carbamic acid and a poor substrate for AChE It is biotransformed by other esterases, but at a much slower rate. A single administration can last as long as 1 hour  CARBACHOL Actions Carbachol profoundly affects both the cardiovascular system and the GIT because of its ganglion- stimulating activity (N receptor effect). It may 1st stimulate then depress these systems. It can cause release of A & NA from the adrenal medulla by its nicotinic action. When locally instilled into the eye, it mimics the effects of ACh, causing miosis (contraction of the pupils) and a spasm of accommodation. Therapeutic uses Rarely used therapeutically except in the eye as a miotic agent to treat glaucoma (by causing pupillary contraction and a decrease in intraocular pressure). Use is limited by its high potency, lack of selectivity & relatively long duration of action. Adverse effects At doses used ophthalmologically, little to no side effects occur. METHACHOLINE Methacholine is a synthetic choline ester It is highly active at all of the M cholinergic receptors, but has little or no effect on the N cholinergic receptors (possible due to the presence of a b- methyl group) It is also resistance to AChE - broken down at a relatively slow rate within the body  METHACHOLINE Clinical use Primarily used to diagnose bronchial hyper-reactivity, which occurs in asthma. Asthmatic patients respond to cholinergic agonists with intense bronchoconstriction, secretions, and reduction in vital capacity Side effects Cardiovascular effects, such as bradycardia and hypotension limit the use of this drug. Use of methacholine, as well as all other M receptor agonists, is contraindicated in patients with coronary insufficiency, gastroduodenal ulcers, and incontinence (inability to control excretory functions) PILOCARPINE The alkaloid pilocarpine is a tertiary amine, and is stable to hydrolysis by AChE It is far less potent than ACh and its derivatives. Pilocarpine exhibits M activity and is used primarily in ophthalmology (selective for M receptors)  PILOCARPINE Actions When applied topically to the cornea, pilocarpine produces a rapid miosis (M 3 stimulation) and contraction of the ciliary muscle (M 3 stimilation) making the lens more convex At this point it is impossible to focus – vision is fixed at to a particular distance. Atropine (M receptor blocker) opposes these effects on the eye Pilocarpine potently stimulates secretions such as sweat, tears, and saliva – but its use is limited due to its lack of selectivity (amongst M receptor subtypes) e.g. its use in Sjogren syndrome or xerostomia (dryness of the mouth) that follows head & neck radiation treatments is limited by its lack of selectivity Adverse effects: Pilocarpine can enter the brain and cause CNS disturbances. It stimulates profuse sweating and salivation  PILOCARPINE – USE IN GALUCOMA Suspensory Pilocarpine is the drug of choice in the emergency ligaments lowering of intraocular pressure of both narrow­angle (also called closed-angle; acute congestive) and wide- angle (also called open-angle; chronic simple) glaucoma. It achieves these because it stimulates the contraction of the smooth muscles of the iris sphincter (resulting in miosis). The iris is then pulled away from the anterior c ciliary muscles hamber opening the trabecular meshwork around Schlemm canal at the base of ciliary muscles causing an immediate drop in intraocular pressure as a result 37 of the increased drainage of aqueous humor. This action lasts up to one day and can be repeated.  CNS APPLICATION OF CHOLINERGIC AGONISTS Selective M1 cholinergic Such a potential agonist receptor agonists have should selectively stimulate been targets for use in the postsynaptic M1 treating cognitive cholinergic receptors imparement in Alzheimer’s without stimulating the disease (where the is presynaptic M2 that inhibit reduced CNS cholinergic the release of endogenous neurotransmission) ACh  INDIRECT-ACTING CHOLINERGIC AGONISTS; ANTICHOLINESTERASES AChE is an enzyme that specifically cleaves ACh to acetate and choline and terminates its actions. It is membrane bound, located both pre- and postsynaptically in the nerve terminal. It is highly concentrated at the postsynaptic end plate of the neuromuscular junction. Drugs that inhibit AChE are called anticholinesterase (anti-ChE) agents. Anti-ChE indirectly provides cholinergic neurotransmission by prolonging the lifespan of ACh at the synaptic space. This results in the accumulation of ACh in the synaptic space provoking a response at all cholinoceptors in the body (both N & M receptors). Due to the widespread distribution of cholinergic neurons in the body, anti-ChE has found application in as toxic agents in the form of agricultural pesticides and potential chemical warfare “nerve gases” (sarin, soman, & tabun). *Therapeutically anti-ChE are used in conditions such as Alzheimer’s disease. These group of agents are classified as either reversible anti-ChE (physostigmine, neostigmine); or irreversible anti-ChE or organophosphates (sarine; isoflurophate)  THERAPEUTIC APPLICATIONS OF ANTI- ACHE Non-obstructive paralytic ileus (paralysis or inactivity of the intestine) - neostigmine is preferred Atony of the bladder – Neostigmine is also preferred Glaucoma and other ophthalmologic indications Glaucoma is characterised by an increase in intraocular pressure, that if sufficiently high & persistent lead to damage of the optic disc at the juncture of the optic nerve and retina: irreversible blindness can occur. Narrow angle (acute congestive; closed- angle) glaucoma is a medical emergency while wide angle (chronic simple) is controlled by continuous drug therapy. Anti-ChE are also used locally in the treatment of accommodative esotropia & mysthenia gravis of the intraocular & eyelid muscles. Also used in Adie (tonic pupil syndrome) resulting from the dysfunction of the ciliary body – physostigmine decreases the blurred vision & pain associated with the condition  THERAPEUTIC APPLICATIONS OF ANTI- ACHE CONT’ Myasthenia gravis: Neuromuscular disease characterised by weakness & marked fatigability of the skeletal muscles caused by autoimmune response primarily to the N ACh receptors at the postjuctional endplate. Symptoms are similar to those seen with curare (muscle relaxant) intoxication. Both respond to anti-ChE therapy. Diagnosis – edrophonium chloride (positive response consists of brief improvement in muscle strength. Treatment – pyridostigmine, neostigmine, & ambenonium are the standard anti-ChE used in the symptomatic treatment of Myasthenia gravis.  THERAPEUTIC APPLICATIONS OF ANTI- ACHE CONT’ Prophylaxis in anti-ChE inhibitor poisoning Pretreatment with pyridostimine the incapacitation and mortality associated with nerve gas poisoning – especially for agents like soman with rapid aging. Given to the military in anticipation of nerve- agent attack. Intoxication by anticholinergic drugs Cholinergic intoxication is caused by anticholinergic agents like atropine, and many other drugs with either central or peripheral anticholinergic activity like phenothiazines, antihistamines, and tricyclic antidepressants. Physostigmine is useful in reversing the central anticholinergic effects of these agents Alzheimer’s disease A deficiency of intact cholinergic neurons, especially those extending from the subcortical areas has been observed in patients with progressive dementia of the Alzheimer’s disease. Tacrine is approved for use in mild to moderate Alzheimer’s disease (limited by a high incident of hepatotoxicity – typical of all the anti-ChE). Other anti-ChE approved for the treatment of Alzheimer’s disease include, donepezil, rivastigmine, & galantamine. ANTICHOLINESTERASES (REVERSIBLE)  PHYSOSTIGMINE Physostigmine is a tertiary amine alkaloid. It is a carbamic acid ester and a substrate of AchE. It forms a relatively stable complex with the enzyme, which then becomes reversibly inactivated. The result is potentiation of cholinergic activity throughout the body. Actions: Physostigmine has a wide range of effects – it lacks selectivity in its actions (because it potentates the effects of ACh). Its duration of action is about 2 to 4 hours. Physostigmine can enter and stimulate the cholinergic sites in the CNS Therapeutic uses: It is used therapeutically stimulate the atonic (non-emptying) bladder. Placed topically in the eye to treat glaucoma, but pilocarpine is more effective. Physostigmine is also used in the treatment of overdoses of drugs with anticholinergic actions, such as atropine, phenothiazines, and tricyclic antidepressants Adverse effects: CNS related convulsions when high doses are used. Bradycardia & a fall in cardiac output may also occur. At higher dose may paralyze skeletal muscles.  NEOSTIGMINE Neostigmine is a synthetic compound that is also a carbamic acid ester. Like physostigmine, it also reversibly inhibits AChE. Unlike physostigmine, neostigmine does not enter the CNS (has a quarternary nitrogen - it is more polar). Its effect on skeletal muscle is greater than that of physostigmine, and it can stimulate contractility before it paralyzes. Its duration of action is 30 min to 2 hours. Therapeutic uses: It is used to stimulate the bladder and GI tract, also used as an antidote for tubocurarine and other competitive neuromuscular blocking agents. Also used in the symptomatic treatment of myasthenia gravis Adverse effects of neostigmine include: Those of generalized cholinergic stimulation, such as salivation, flushing, decreased blood pressure, nausea, abdominal pain, diarrhea, and bronchospasms.  PYRIDOSTIGMINE AND AMBENONIUM Pyridostigmine & ambemonium are other AChE inhibitors that are used in the chronic management of myasthenia gravis. Their durations of action is 3 to 6 hours and 4 to 8 hours, respectively  EDROPHONIUM The actions of edrophonium are similar to those of neostigmine, except that it is more rapidly absorbed and has a short duration of action (10 to 20 minutes) Edrophonium is a quarternary amine and is used in the diagnosis of myasthenia gravis IV injection of edrophonium leads to a rapid increase in muscle strength Care must be taken, because excess drug may provoke a cholinergic crisis. Atropine is the antidote  TACRINE, DONEPEZIL, RIVASTIGMINE, & GALANTAMINE Patients with Alzheimer’s disease have a deficiency of cholinergic neurons in the CNS. This observation led to the development of anticholinesterases as possible remedies for the loss of cognitive function. Tacrine was 1st available, but it has been replaced by the others because of its hepatotoxicity. Despite their ability to delay the progression of the disease – they do not stop its progression of the disease. GIT distress is their primary adverse effect.  ANTICHOLINESTERASES (IRREVERSIBLE) Most organic derivatives of phosphoric acid (organophosphate) have the capacity to bind covalently to AChE. The result is a long-lasting increase in ACh at all sites where it is released. However many of these drugs are extremely toxic and were developed by the military as nerve agents e.g. Sarine in the Tokyo subway (20 March 1995). Related compounds, such as parathion, are employed as insecticides. Recently the use of organophosphate insecticides has been replaced by less toxic reversible carbamates such as carbaryl, propoxur (Baygon®), and aldicarb. Isoflurophate (diisopropyl fluorophosphate; DFP) is the prototype agent.  ISOFLUROPHATE Mechanism of action: Isoflurophate is an organophosphate that covalently binds to the active site of AChE (phosphorylating the enzyme). If the alkyl groups of the phosphorylated enzyme are ethyl or methyl, spontaneous regeneration occurs within several hours. Secondary & tertiary alkyl groups (like isopropyl of isoflurophate) further strengthens the stability of the covalent bond – significant regeneration of the active enzyme is no longer observed. The enzyme is then permanently inactivated – restored by the synthesis of new enzyme molecules. These process by which the phosphorylated enzyme slowly releases one of its alkyl groups is called “aging”. “Aging” makes it impossible for chemical reactivators, such as pralidoxime (PAM) , to break the bond between the remaining drug and the enzyme because “aging” strengthens the phosphorylation of the enzyme. DFP ages in 6 to 8 hours, whereas newer nerve agents, available to the military, age in minutes or seconds. Actions: Cause generalized cholinergic stimulation, paralysis of motor function, intense miosis, and convulsions. Atropine in high dosage can reverse many of the muscarinic and central effects of isoflurophate Therapeutic uses: An ophthalmic ointment of the drug is used topically in the eye for the chronic treatment of open-angle glaucoma. The effects may last for up to one week after a single administration. Echothiophate also covalently binds to acetylcholinesterase, and has largely replaced isoflurophate as a therapy for open-angle glaucoma  CHOLINESTERASE REACTIVATORS Oximes like pralidoxime (pyridine-2-aldoxime methyl chloride; PAM) and obidoxime (1,1'-(Oxydimethylene)bis(4-formylpyridinium) dioxime chloride; HI-6) are capable of reactivating inhibited AChE enzyme more rapidly than does spontaneous hydrolysis. The presence of a charged group allows them to approach an anionic Mechanismof aging site on the enzyme, where it essentially displaces the organophosphate and regenerates the enzyme. If given before aging of the enzyme occurs, they can reverse the effects of isoflurophate, except for those in the CNS (because they do not cross the BBB). PAM is less effective against newer nerve agents - because aging occurs more rapidly. The reactivating effects of oximes are more evident at the neuromuscular junction – IV administration restores response to stimulation of the motor nerve within few minutes. The antidotal effects of oximes are minimal at the autonomic effector sites & their entry into the CNS is restricted by their quaternary ammonium group. High doses of oximes inhibit the AChE enzyme and causes neuromuscular blockade – care should be exercised when these agents are administered Current antidotal therapy for organophosphate exposure resulting from warfare or terrorism includes: 57 Atropine An oxime A benzodiazipine as an anticonvulsant 64 SUMMARY  PRACTICE SCENARIO A 65-year old man with urinary A. Why is he treated with this retention and inadequate drug? emptying of the bladder is B. What side effects should he being treated with be aware of while taking bethanechol. bethanechol? C. What are the contraindications to the use of bethanechol?  PRACTICE SCENARIO A 23-year old woman is brought A. What is the MOA of to the emergency room after organophsophates? deliberately ingesting a bottle of B. What symptoms is she likely organophosphate insecticide. to experience and what is the timeframe that these symptoms might appear? C. What is the appropriate treatment?