The interaction between hippocampal cholinergic and nitrergic neurotransmission coordinates NMDA-dependent behavior and autonomic changes induced by contextual fear retrieval.

RATIONALE: Re-exposing an animal to an environment previously paired with an aversive stimulus evokes large alterations in behavioral and cardiovascular parameters. Dorsal hippocampus (dHC) receives important cholinergic inputs from the basal forebrain, and respective acetylcholine (ACh) levels are described to influence defensive behavior. Activation of muscarinic M1 and M3 receptors facilitates autonomic and behavioral responses along threats. Evidence show activation of cholinergic receptors promoting formation of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) in dHC. Altogether, the action of ACh and NO on conditioned responses appears to converge within dHC. OBJECTIVES: As answer about how ACh and NO interact to modulate defensive responses has so far been barely addressed, we aimed to shed additional light on this topic. METHODS: Male Wistar rats had guide cannula implanted into the dHC before being submitted to the contextual fear conditioning (3footshocks/085 mA/2 s). A catheter was implanted in the femoral artery the next day for cardiovascular recordings. Drugs were delivered into dHC 10 min before contextual re-exposure, which occurred 48 h after the conditioning procedure. RESULTS: Neostigmine (Neo) amplified the retrieval of conditioned responses. Neo effects (1 nmol) were prevented by the prior infusion of a M1-M3 antagonist (fumarate), a neuronal nitric oxide synthase inhibitor (NPLA), a NO scavenger (cPTIO), a guanylyl cyclase inhibitor (ODQ), and a NMDA antagonist (AP-7). Pretreatment with a selective M1 antagonist (pirenzepine) only prevented the increase in autonomic responses induced by Neo. CONCLUSION: The results show that modulation in the retrieval of contextual fear responses involves coordination of the dHC M1-M3/NO/cGMP/NMDA pathway.

Critical role of hippocampal muscarinic acetylcholine receptors on memory reconsolidation in mice.

Over the years, experimental and clinical evidence has given support to the idea that acetylcholine (Ach) plays an essential role in mnemonic phenomena. On the other hand, the Hippocampus is already known to have a key role in learning and memory. What is yet unclear is how the Ach receptors may contribute to this brain region role during memory retrieval. The Ach receptors are divided into two broad subtypes: the ionotropic nicotinic acetylcholine receptors and the metabotropic muscarinic acetylcholine receptors. Back in 2010, we demonstrated for the first time the critical role of hippocampal α7 nicotinic acetylcholine receptors in memory reconsolidation process of an inhibitory avoidance response in mice. In the present work, we further investigate the possible implication of hippocampal muscarinic Ach receptors (mAchRs) in this process using a pharmacological approach. By specifically administrating agonists and antagonists of the different mAchRs subtypes in the hippocampus, we found that M1 and M2 but not M3 subtype may be involved in memory reconsolidation processes in mice.

Novel choline analog 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol produces sympathoinhibition, hypotension, and antihypertensive effects.

The search for new drugs remains an important focus for the safe and effective treatment of cardiovascular diseases. Previous evidence has shown that choline analogs can offer therapeutic benefit for cardiovascular complications. The current study investigates the effects of 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol (LQFM032) on cardiovascular function and cholinergic-nitric oxide signaling. Synthesized LQFM032 (0.3, 0.6, or 1.2 mg/kg) was administered by intravenous and intracerebroventricular routes to evaluate the potential alteration of mean arterial pressure, heart rate, and renal sympathetic nerve activity of normotensive and hypertensive rats. Vascular function was further evaluated in isolated vessels, while pharmacological antagonists and computational studies of nitric oxide synthase and muscarinic receptors were performed to assess possible mechanisms of LQFM032 activity. The intravenous and intracerebroventricular administration of LQFM032 elicited a temporal reduction in mean arterial pressure, heart rate, and renal sympathetic nerve activity of rats. The cumulative addition of LQFM032 to isolated endothelium-intact aortic rings reduced vascular tension and elicited a concentration-dependent relaxation. Intravenous pretreatment with L-NAME (nitric oxide synthase inhibitor), atropine (nonselective muscarinic receptor antagonist), pirenzepine, and 4-DAMP (muscarinic M1 and M3 subtype receptor antagonist, respectively) attenuated the cardiovascular effects of LQFM032. These changes may be due to a direct regulation of muscarinic signaling as docking data shows an interaction of choline analog with M1 and M3 but not nitric oxide synthase. Together, these findings demonstrate sympathoinhibitory, hypotensive, and antihypertensive effects of LQFM032 and suggest the involvement of muscarinic receptors.

Central muscarinic and LPBN mechanisms on sodium intake.

Central cholinergic activation stimulates water intake, but also NaCl intake when the inhibitory mechanisms are blocked with injections of moxonidine (α2 adrenergic/imidazoline agonist) into the lateral parabrachial nucleus (LPBN). In the present study, we investigated the involvement of central M1 and M2 muscarinic receptors on NaCl intake induced by pilocarpine (non-selective muscarinic agonist) intraperitoneally combined with moxonidine into the LPBN or by muscimol (GABAA agonist) into the LPBN. Male Holtzman rats with stainless steel cannulas implanted bilaterally in the LPBN and in the lateral ventricle were used. Pirenzepine (M1 muscarinic antagonist, 1 nmol/1 µl) or methoctramine (M2 muscarinic antagonist, 50 nmol/1 µL) injected intracerebroventricularly (i.c.v.) reduced 0.3 M NaCl and water intake in rats treated with pilocarpine (0.1 mg/100 g of body weight) injected intraperitoneally combined with moxonidine (0.5 nmol/0.2 µL) into the LPBN. In rats treated with muscimol (0.5 nmol/0.2 µL) into the LPBN, methoctramine i.c.v. also reduced 0.3 M NaCl and water intake, however, pirenzepine produced no effect. The results suggest that M1 and M2 muscarinic receptors activate central pathways involved in the control of water and sodium intake that are under the influence of the LPBN inhibitory mechanisms.

PKC delta activation increases neonatal rat retinal cells survival in vitro: Involvement of neurotrophins and M1 muscarinic receptors.

Protein kinase C (PKC) is a family of serine/threonine kinases related to several phenomena as cell proliferation, differentiation and survival. Our previous data demonstrated that treatment of axotomized neonatal rat retinal cell cultures for 48 h with phorbol 12-myristate 13-acetate (PMA), a PKC activator, increases retinal ganglion cells (RGCs) survival. Moreover, this treatment decreases M1 receptors (M1R) and modulates BDNF levels. The aim of this work was to assess the possible involvement of neurotrophins BDNF and NGF in the modulation of M1R levels induced by PKC activation, and its involvement on RGCs survival. Our results show that PMA (50 ng/mL) treatment, via PKC delta activation, modulates NGF, BDNF and M1R levels. BDNF and NGF mediate the decrease of M1R levels induced by PMA treatment. M1R activation is essential to PMA neuroprotective effect on RGCs as telenzepine (M1R selective antagonist) abolished it. Based on our results we suggest that PKC delta activation modulates neurotrophins levels by a signaling pathway that involves M1R activation and ultimately leading to an increase in RGCs survival in vitro.

Muscarinic presynaptic modulation in GABAergic pallidal synapses of the rat.

The external globus pallidus (GPe) is central for basal ganglia processing. It expresses muscarinic cholinergic receptors and receives cholinergic afferents from the pedunculopontine nuclei (PPN) and other regions. The role of these receptors and afferents is unknown. Muscarinic M1-type receptors are expressed by synapses from striatal projection neurons (SPNs). Because axons from SPNs project to the GPe, one hypothesis is that striatopallidal GABAergic terminals may be modulated by M1 receptors. Alternatively, some M1 receptors may be postsynaptic in some pallidal neurons. Evidence of muscarinic modulation in any of these elements would suggest that cholinergic afferents from the PPN, or other sources, could modulate the function of the GPe. In this study, we show this evidence using striatopallidal slice preparations: after field stimulation in the striatum, the cholinergic muscarinic receptor agonist muscarine significantly reduced the amplitude of inhibitory postsynaptic currents (IPSCs) from synapses that exhibited short-term synaptic facilitation. This inhibition was associated with significant increases in paired-pulse facilitation, and quantal content was proportional to IPSC amplitude. These actions were blocked by atropine, pirenzepine, and mamba toxin-7, suggesting that receptors involved were M1. In addition, we found that some pallidal neurons have functional postsynaptic M1 receptors. Moreover, some evoked IPSCs exhibited short-term depression and a different kind of modulation: they were indirectly modulated by muscarine via the activation of presynaptic cannabinoid CB1 receptors. Thus pallidal synapses presenting distinct forms of short-term plasticity were modulated differently.

In vitro effects of the organophosphorus pesticide malathion on the reactivity of rat aorta.

BACKGROUND AND PURPOSE: There is a remarkable paucity of studies analyzing the role of the endothelium-derived relaxing factors on the vascular effects of organophosphates. This study was carried out to evaluate the vascular effects of malathion and the role of nitric oxide (NO) and prostacyclin (PGI2). METHODS: Vascular reactivity measuring isometric forces in vitro ('organ chambers') and flow cytometry (cells loaded with DAF-FM DA) were used. RESULTS: In rat thoracic aorta segments contracted with phenylephrine (Phe) (10(-7) mol/l), malathion (10(-10) to 10(-5) mol/l) induced concentration-dependent relaxation in arteries with intact endothelium (n = 7; p < 0.05). Malathion-mediated relaxation was blocked by N-nitro-L-arginine methyl ester (L-NAME; 10(-4) mol/l), a nonspecific NO synthase inhibitor, and/or indomethacin (10(-5) mol/l), a nonspecific cyclooxygenase inhibitor (n = 10, p < 0.05). In thoracic aorta rings, with and without endothelium, Phe (10(-10) to 10(-5) mol/l) evoked concentration-dependent contraction, which was reduced in the presence of malathion. In rings with or without endothelium, incubated with malathion, L-NAME and indomethacin, the Phe-induced contraction was restored. The role of NO was confirmed using flow cytometry. Malathion evokes endothelium-dependent relaxation through the M1 muscarinic receptor, since this relaxation was clearly blocked by atropine (M1 and M2 blocker) and pirenzepine (M1 blocker), but was less blocked by gallamine (M2 blocker) or 4-DAMP (M3 blocker). CONCLUSIONS: These findings suggest that the organophosphate compound effects on vascular reactivity depend of NO and PGI2.

The potency and efficacy of anticholinergics to inhibit haloperidol-induced catalepsy in rats correlates with their rank order of affinities for the muscarinic receptor subtypes.

Extrapyramidal syndromes (EPS) caused by antipsychotic therapy are currently treated with anticholinergics that lack selectivity for the five muscarinic receptor subtypes. Since these receptors are heterogeneously expressed among the different classes of striatal neurons and their afferents, it can be expected that their simultaneous blockade will cause distinct, sometimes opposed, effects within the striatal circuitry. In order to test the hypothesis that the differential blockade of the muscarinic receptor subtypes would influence their potency and efficacy to prevent EPS, here we tested four anticholinergics with varying order of affinities for the muscarinic receptor subtypes, and compared their dose-response curves to inhibit haloperidol-induced catalepsy in male rats. Drugs were applied into the lateral ventricle 15 min before haloperidol (2 mg/kg, s.c.). Catalepsy was measured in the bar test at 15 min intervals during 5 h. The preferential M1/M4 antagonist pirenzepine (3, 10, 30, 100, and 300 nmol) caused a dose-dependent inhibition of catalepsy intensity: ED50 = 5.6 nmol [95% CI, 3.9-8.1], and latency: ED50 = 5.6 nmol [95% CI, 3.7-8.6]. Pirenzepine had the steepest dose-response curve, producing maximal inhibition (84 ± 5%) at the dose of 10 nmol, while its effect tended to reverse at higher doses (62 ± 11%). The purported M1/M3 antagonist 4-DAMP (30, 100, and 300 nmol) also caused a dose-dependent inhibition of catalepsy intensity: ED50 = 29.5 nmol [95% CI, 7.0 to 123.0], and latency: ED50 = 28.5 nmol [95% CI, 2.2 to 362.0]. However, the curve for 4-DAMP had a less pronounced slope, reaching its maximal effect (63 ± 14%) at the dose of 300 nmol. The M2/M4 antagonist AF-DX 116 (10, 30, and 300 nmol) only caused a partial inhibition of catalepsy (30 ± 11%) at the dose of 30 nmol, but this changed to a non-significant increment (15 ± 10%) at the dose of 100 nmol. The alleged M4 antagonist tropicamide (30, 100, 300, and 600 nmol) produced a partial inhibition of catalepsy (36 ± 12%) at the dose of 300 nmol, but lacked effect at higher or lower doses. Concurrent treatment with pirenzepine (10 nmol) and tropicamide (300 nmol) produced an effect similar to that of tropicamide alone. The greater potency and efficacy of pirenzepine for catalepsy inhibition could be due to its higher affinity for M1 receptors and, to a lesser extent, for M4 receptors. It is suggested that selective M1 antagonists would be more effective than M2, M3 or M4 antagonists to prevent EPS caused by antipsychotic drugs.

Paradoxical neostigmine-induced TOFfade: on the role of presynaptic cholinergic and adenosine receptors.

Neuromuscular transmission is clinically monitored using the train-of-four ratio (TOFratio), which is the quotient between twitch tension produced by the fourth (T4) and by the first (T1) stimulus within a train-of-four stimulation at 2Hz. Neostigmine causes a paradoxical depression of the TOFratio (TOFfade) that is amplified by intra-arterial atropine in cats. This led us to question the usefulness of the TOFratio as a sole testing element to control neostigmine-induced reversal of neuromuscular transmission block caused by non-depolarizing agents. We hypothesized that the inhibition of cholinesterase activity might increase acetylcholine bioavailability and consequently cholinoceptor activation, leading to concomitant adenosine release from nerve endings and skeletal muscle fibers. The involvement of presynaptic muscarinic and adenosine receptors in neostigmine-induced TOFfade in the rat phrenic nerve diaphragm was investigated. Blockade of adenosine A2A receptors with ZM241385 and of muscarinic M2 receptors with methoctramine or atropine amplified neostigmine-induced TOFfade. Notwithstanding TOFfade amplification, the blockade of M2 or A2A receptors increased both T1 and T4 twitch tensions above control during the first 3min of neostigmine application. Beyond that period, the T1 twitch tension returned to baseline, whereas T4 decreased further until the control value with neostigmine alone. Blockade of M1 receptors by pirenzepine did not change neostigmine-induced TOFfade, unless A2A receptors were concurrently blocked with ZM241385. Data indicate that the paradoxical neostigmine-induced fade involves presynaptic mechanisms that regulate transmitter release and synaptic adenosine accumulation, including the activation of adenosine A2A and muscarinic M2 receptors.

Síntomas de discontinuación luego de suspensión abrupta de olanzapina / Discontinuation symptoms following olanzapine abrupt withdrawal

Extended use of atypical neuroleptics in clinical practice, may be explained by their effectiveness as antipsychotics and also with recent approvals for therapeutic benefits of this drugs beyond psychotic disorders. Receptor adaptation mechanisms rises critical issues about treatment discontinuation strategies. Clinical data of two patients who have required the use of atypical antipsychotics are discussed. In both cases, abrupt discontinuation of the drug occurred followed by the emergence of extrapyramidal symptoms. Adaptation mechanisms in synaptic structures would be responsible for this phenomena and the subsequent amelioration of this extrapyramidal symptoms when initial treatment is replaced. The authors concluded that atypical antipsychotics, as other psychotropic agents shouldn't be abruptly discontinued even when they are replaced by other drugs from the same family.

El uso de los antipsicóticos atípicos ha ido aumentando con el tiempo entre otras cosas, por el hecho de que se están usando no sólo para los cuadros psicóticos sino que también para otras patologías. Como con otros fármacos que actúan a nivel de receptores deben considerarse los mecanismos de adaptación receptorial que se producen con su uso. Lo anterior es de suma importancia cuando pensamos en la discontinuación del tratamiento y en sus formas de hacerlo. En este trabajo presentamos dos casos clínicos de pacientes que han requerido el uso de antipsicóticos atípicos. En ambos casos se ha realizado una suspensión brusca del fármaco lo que ha generado la aparición de síntomas extrapiramidales, que en nuestra opinión, son explicados por mecanismos de adaptación a nivel sináptico y que han disminuido con el reinicio del tratamiento inicial. Debemos tener presente que estos fármacos no deben ser discontinuados en forma súbita aun cuando sean remplazados por otros de la misma familia.

Modulation of peripheral inflammatory pain thresholds by M(1) and nicotinic receptor antagonists.

The study used the paw withdrawal test to investigate the role of the cholinergic system on the modulation of inflammatory pain induced by carrageenan (Cg) at the peripheral level, through activation of muscarinic and nicotinic receptors. Intraplantar administration of the specific M(1) receptor antagonist telenzepine (TEL; 6, 12 and 24 µg/paw) caused a dose-dependent reduction in the nociceptive threshold induced by Cg (125 µg/paw). This effect was not observed with increasing doses (4, 10 and 40 µg) of other specific receptor antagonists: M(2) (dimethindene), M(3) (4-DAMP) and M(4) (tropicamide). The nicotinic antagonist mecamylamine (MEC; 25, 50 and 100 µg/paw) also caused a dose-dependent reduction in the nociceptive threshold induced by Cg (125 µg). To exclude a non-local effect, Cg (125 µg) was injected into both hind paws, while TEL (12 µg) and MEC (50 µg) were administered only in the right paw. At these doses, the muscarinic antagonists increased inflammatory pain only in the treated right paw, suggesting a peripheral effect. In the presence of prostaglandin E(2) (1 µg/paw), TEL (12 µg) and MEC (50 µg) did not reduce the nociceptive threshold, suggesting that this hyperalgesic agent does not induce the release of endogenous acetylcholine. These data suggest that muscarinic M(1) and nicotinic receptors participate in the modulation of endogenous cholinergic inflammatory pain at the peripheral level.

Characterization of a new muscarinic toxin from the venom of the Brazilian coral snake Micrurus lemniscatus in rat hippocampus.

AIMS: We have isolated a new muscarinic protein (MT-Mlα) from the venom of the Brazilian coral snake Micrurus lemniscatus. MAIN METHODS: This small protein, which had a molecular mass of 7,048Da, shared high sequence homology with three-finger proteins that act on cholinergic receptors. The first 12 amino acid residues of the N-terminal sequence were determined to be: Leu-Ile-Cys-Phe-Ile-Cys-Phe-Ser-Pro-Thr-Ala-His. KEY FINDINGS: The MT-Mlα was able to displace the [(3)H]QNB binding in the hippocampus of rats. The binding curve in competition experiments with MT-Mlα was indicative of two types of [(3)H]QNB-binding site with pK(i) values of 9.08±0.67 and 6.17±0.19, n=4, suggesting that various muscarinic acetylcholine receptor (mAChR) subtypes may be the target proteins of MT-Mlα. The MT-Mlα and the M(1) antagonist pirenzepine caused a dose-dependent block on total [(3)H]inositol phosphate accumulation induced by carbachol. The IC(50) values for MT-Mlα and pirenzepine were, respectively, 33.1 and 2.26 nM. Taken together, these studies indicate that the MT-Mlα has antagonist effect on mAChRs in rat hippocampus. SIGNIFICANCE: The results of the present study show, for the first time, that mAChRs function is drastically affected by MT-Mlα since it not only has affinity for mAChRs but also has the ability to inhibit mAChRs.

Cholinergic autoantibodies from primary Sjögren's syndrome modulate submandibular gland Na+/K+-ATPase activity via prostaglandin E2 and cyclic AMP.

We demonstrate that patients with primary Sjögren's syndrome (pSS) produce functional IgG autoantibodies that interact with the glandular M(3) muscarinic acetylcholine receptors (mAChRs). These autoantibodies act as a partial muscarinic agonist, increasing prostaglandin E(2) (PGE(2)) and cyclic AMP production through modifying Na(+)/K(+)-ATPase activity, but also interfere with the secretory effect of the parasympathetic neurotransmitter. The IgG from patients with pSS has two effects on the submandibular gland. On the one hand, it may act as an inducer of the proinflammatory molecule (PGE(2)) that, in turn, inhibits Na(+)/K(+)-ATPase activity. On the other hand, it plays a role in the pathogenesis of dry mouth, abolishing the Na(+)/K(+)-ATPase inhibition and the net K(+) efflux stimulation of the salivary gland in response to the authentic agonist pilocarpine, decreasing salivary fluid production.

Presynaptic M1, M2, and A1 receptors play roles in tetanic fade induced by pancuronium or cisatracurium.

PURPOSE: We investigated whether presynaptic facilitatory M1 and/or inhibitory M2 muscarinic receptors contributed to pancuronium- and cisatracurium-induced tetanic fade. METHODS: Phrenic nerve-diaphragm muscle preparations of rats were indirectly stimulated with tetanic frequency (75 +/- 3.3 Hz; mean +/- SD). Doses of pancuronium, cisatracurium, hexamethonium, and d-tubocurarine for producing approximately 25% fade were determined. The effects of pirenzepine and methoctramine, blockers of presynaptic M1 and M2 receptors, respectively, on the tetanic fade were investigated. RESULTS: The concentrations required for approximately 25% fade were 413 microM for hexamethonium (26.8 +/- 2.4% 4% fade), 55 nM for d-tubocurarine (28.7 +/- 2.55% fade), 0.32 microM for pancuronium (25.4 +/- 2.2% fade), and 0.32 microM for cisatracurium (24.7 +/- 0.8% fade). Pirenzepine or methoctramine alone did not produce the fade. Methoctramine, 1 microM, attenuated the fade induced by hexamethonium (to 16.0 +/- 2.5% fade), d-tubocurarine (to 6.0 +/- 1.6 fade), pancuronium (to 8.0 +/- 4.0% fade), and cisatracurium (to 11.0 +/- 3.3% fade). 10 nM pirenzepine attenuated only the fades produced by pancuronium (to 5.0 +/- 0.11% fade) and cisatracurium (to 13.3 +/- 5.3% fade). Cisatracurium (0.32 microM) showed antiacetylcholinesterase activity (in plasma, 14.2 +/- 1.6%; 6%; in erythrocyt 17.2 +/- 2.66%) similar to that of pancuronium (0.32 microM). The selective A1 receptor blocker, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 2.5 nM), also attenuated the fades induced by pancuronium and cisatracurium. CONCLUSION: The tetanic fades produced by pancuronium and cisatracurium depend on the activation of presynaptic inhibitory M2 receptors; these agents also have anticholinesterase activities. The fades induced by these agents also depend on the activation of presynaptic inhibitory A1 receptors through the activation of stimulatory M1 receptors by acetylcholine.

Central muscarinic receptor subtypes involved in pilocarpine-induced salivation, hypertension and water intake.

BACKGROUND AND PURPOSE: Recent evidence has suggested that pilocarpine (ACh receptor agonist) injected peripherally may act centrally producing salivation and hypertension. In this study, we investigated the effects of specific M(1) (pirenzepine), M(2)/M(4) (methoctramine), M(1)/M(3) (4-DAMP) and M(4) (tropicamide) muscarinic receptor subtype antagonists injected into the lateral cerebral ventricle (LV) on salivation, water intake and pressor responses to peripheral pilocarpine. EXPERIMENTAL APPROACH: Male Holtzman rats with stainless steel cannulae implanted in the LV were used. Salivation was measured in rats anaesthetized with ketamine (100 mg per kg body weight) and arterial pressure was recorded in unanaesthetized rats. KEY RESULTS: Salivation induced by i.p. pilocarpine (4 micromol per kg body weight) was reduced only by 4-DAMP (25-250 nmol) injected into the LV, not by pirenzepine, methoctramine or tropicamide at the dose of 500 nmol. Pirenzepine (0.1 and 1 nmol) and 4-DAMP (5 and 10 nmol) injected into the LV reduced i.p. pilocarpine-induced water intake, whereas metoctramine (50 nmol) produced nonspecific effects on ingestive behaviours. Injection of pirenzepine (100 nmol) or 4-DAMP (25 and 50 nmol) into the LV reduced i.v. pilocarpine-induced pressor responses. Tropicamide (500 nmol) injected into the LV had no effect on pilocarpine-induced salivation, pressor responses or water intake. CONCLUSIONS AND IMPLICATIONS: The results suggest that central M(3) receptors are involved in peripheral pilocarpine-induced salivation and M(1) receptors in water intake and pressor responses. The involvement of M(3) receptors in water intake and pressor responses is not clear because 4-DAMP blocks both M(1) and M(3) receptors.

[Adjunctive therapies to glycaemic control of type 1 diabetes mellitus]. / Adjuvantes no tratamento da hiperglicemia do diabetes melito tipo 1.

Since Diabetes Control and Complications Trial (DCCT), intensive therapy has been directed at achieving glucose and glycosylated hemoglobin (HbA1c) values as close to normal as possible regarding safety issues. However, hyperglycemia (especially postprandial hyperglycemia) and hypoglicemia continue to be problematic in the management of type 1 diabetes. The objective of associating other drugs to insulin therapy is to achieve better metabolic control lowering postprandial blood glucose levels. Adjunctive therapies can be divided in four categories based on their mechanism of action: enhancement of insulin action (e.g. the biguanides and thiazolidinediones), alteration of gastrointestinal nutrient delivery (e.g. acarbose and amylin) and other targets of action (e.g. pirenzepine, insulin-like growth factor I and glucagon-like peptide-1). Many of these agents have been found to be effective in short-term studies with decreases in HbA1c of 0.5-1%, lowering postprandial blood glucose levels and decreasing daily insulin doses.

Adjuvantes no tratamento da hiperglicemia do diabetes melito tipo 1: [revisão] / Adjunctive therapies to glycaemic control of type 1 diabetes mellitus: [review]

Desde o Diabetes Control and Complications Trial (DCCT), a terapia insulínica intensiva tem sido direcionada para alcançar valores de glicemia e hemoglobina glicada (HbA1c) tão próximos do normal quanto a segurança permita. Entretanto, a hiperglicemia (especialmente a hiperglicemia pós-prandial) e a hipoglicemia continuam a ser um problema no manejo do diabetes tipo 1. O objetivo de associar outras drogas à terapia insulínica é diminuir a glicemia pós-prandial. A terapia adjunta pode ser dividida em três grupos, conforme seu mecanismo de ação: 1. Aumento da ação da insulina (metformina e tiazolidinedionas); 2. Alteração da liberação de nutrientes no trato gastrintestinal (acarbose e amilina); 3. Outros modos de ação [pirenzepina, fator de crescimento insulina-símile (IGF-1) e peptídeo semelhante ao glucagon 1 (GLP-1). Muitos desses agentes mostraram, em estudos de curto prazo, diminuição de 0,5 por cento a 1 por cento na HbA1c, diminuir a hiperglicemia pós-prandial e as doses diárias de insulina.

Since Diabetes Control and Complications Trial (DCCT), intensive therapy has been directed at achieving glucose and glycosylated hemoglobin (HbA1c) values as close to normal as possible regarding safety issues. However, hyperglycemia (especially postprandial hyperglycemia) and hypoglicemia continue to be problematic in the management of type 1 diabetes. The objective of associating other drugs to insulin therapy is to achieve better metabolic control lowering postprandial blood glucose levels. Adjunctive therapies can be divided in four categories based on their mechanism of action: enhancement of insulin action (e.g. the biguanides and thiazolidinediones), alteration of gastrointestinal nutrient delivery (e.g. acarbose and amylin) and other targets of action (e.g. pirenzepine, insulin-like growth factor I and glucagon-like peptide-1). Many of these agents have been found to be effective in short-term studies with decreases in HbA1c of 0.5-1 percent, lowering postprandial blood glucose levels and decreasing daily insulin doses.

Anti-brain cholinergic auto antibodies from primary Sjögren syndrome sera modify simultaneously cerebral nitric oxide and prostaglandin biosynthesis.

The presence of circulating antibodies from primary Sjögren Syndrome (pSS) patients enable to interact with rat cerebral frontal cortex by activating muscarinic acetylcholine receptors (mAChR). ELISA assay for PGE2 generation, nitric oxide synthase (NOS) activity was measured in cerebral frontal cortex slices by production of [U-14C]-citruline and mRNA isolation/quantitative PCR for COX-1 and COX-2 gene expression were carried out. By ELISA assay, it was shown that IgG from pSS patients reacted to cerebral frontal cortex cell surface and with human M1 and M3 mAChR. Beside pSS IgG displayed an agonistic-like activity stimulating NOS activity and PGE2 production associated with an increased COX-1 mRNA gene expression, without affecting COX-2 mRNA levels. Inhibition of phospholipase A2 (PLA2) and NOS prevented pSS IgG effects upon both PGE2 production and COX-1 mRNA levels. The results support the notion that serum IgG auto antibodies in pSS patients target cerebral mAChR may have pathogenic role in immune neuroinflammation and on cognitive dysfunction present in pSS patients.

Aging-induced decrease of cholinergic response and calcium sensitivity on rat jejunum contractions.

The role of aging on contraction or relaxation through muscarinic or alpha-adrenergic receptors, respectively, was studied in isolated rat jejunum. Furthermore, the influence of extracellular calcium was analyzed, through functional and radioligand binding assays. The rank order of potency for selective muscarinic antagonists for M(1), M(2), and M(3) receptor subtypes, measured from affinity (pA(2)) values, was p-fluorohexahydrosiladifenidol (pFHHSiD) (M(3)) > pirenzepine (M(1)) > methoctramine (M(2)), indicating a predominance of M(3) subtype. This order was unchanged with age. Contractions by muscarinic agonist methacholine (MCh) were diminished in aged rats, resulting in lower apparent affinity (pD(2)) values, compared with adult controls. A larger decrease of MCh contractions occurred in aged rats after Ca(2+) withdrawal or after the calcium channel blocker isradipine. Changes were not detected for relaxation by adrenergic agonists. In conclusion, aging caused a decrease of MCh potency, which is probably related to the reduction of calcium sensitivity in jejunum.

Muscarinic cholinoceptor activation modulates DNA synthesis and CD40 expression in fibroblast cells.

1 The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChR) on DNA synthesis and CD40 expression in human fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with carbachol in presence or absence of specific antagonists and the following parameters were measured: identification of mAChR subtypes, DNA synthesis, inositol phosphates (InsP) production and CD40 expression. 2 Human fibroblasts express mAChR with Kd 0.47 +/- 0.11 nm and Bmax 236 +/- 22 fmol mg protein(-1). Carbachol stimulates DNA synthesis, InsP and the expression of CD40. All these effects were inhibited by atropine, mustard hydrochloride (4-DAMP) and pirenzepine but not by AF-DX 116 and tropicamide, indicating that M3 and M1 mAChR are implicated in carbachol action. The relative Ki of the antagonists obtained by competition binding assay was in parallel to the relative potency for blocking both carbachol-stimulated InsP accumulation and DNA synthesis. 3 The intracellular pathway leading to carbachol-induced biological effects involved phospholipase C and calcium/calmodulin, as U-73122 and trifluoroperazine blocked carbachol effects, respectively. Calphostin C, a protein kinase C inhibitor, had no effect, indicating that this enzyme does not participate in the system. 4 These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on normal human fibroblast function.