Muscarinic cholinergic stimulation of phosphatidylinositol turnover in the longitudinal smooth muscle of guinea-pig ileum.

1. The metabolism of phosphatidylinositol and phosphatidate was investigated in fragments of longitudinal smooth muscle from guinea-pig ileum incubated with cholinergic and anticholinergic drugs. 2. Incorporation of Pi into these lipids was enhanced by acetylcholine and carbamoylcholine. 3. The receptor responsible for triggering this response was of the muscarinic type, since (a) the response was also produced by the muscarinic agonists acetyl-beta-methylcholine, carbamoyl-beta-methylcholine and pilocarpine, and (b) the response was prevented by atropine and prophylbenzilylcholine mustard, but not by tubocurarine. 4. Increased phosphatidylinositol labellin was clearly observed within 5 min in tissue treated with a high concentration of carbamoylcholine. 5. Halfmaximal stimulation of phosphatidylinositol labelling occurred at approx. 10 muM-muM-carbamoylcholine. 6. Incubation of muscle fragments with carbamoylcholine provoked a decrease in phosphatidylinositol concentration, as would be expected if phosphatidyl-inositol breakdown is the reaction controlled by agonists. 7. This information all appears consistent with the proposal that phosphatidylinositol breakdown may be a reaction intrinsic to the mechanisms of muscarinic cholinergic receptor systems.     

Scopolamine self-administration: Cholinergic involvement in reward mechanisms

Naive rats readily learned to self-administer scopolamine, a centrally active anticholinergic antimuscarinic agent, by the intravenous route; drug intake remained constant while response rates decreased with increasing unit dose ((0.005–0.02 mg/kg/infusion). Increases and decreases in scopolamine responding were elicited by pretreatment with muscarinic agonists and antagonists, respectively. An anticholinergic action at muscarinic synapses appears to be sufficient for reinforcing efficacy; such an action may mediate, in part, the addictive properties of other drugs (e.g., opiates and phencyclidine-like hallucinogens) that are known to have anticholinergic effects.     

Effect of anticholinergic drugs alone and in combination with nembutal on burst theta-neurons of the rabbit septum

Activity of neurones with rhythmic theta-bursts was recorded in the medial septum--diagonal band complex of the waking rabbits with intact and deafferented septum. Effects of anticholinergic (scopolamine, atropine) and cholinomimetic (physostigmine) drugs were investigated after i.v. injection. Cholinoblocking drugs in doses, suppressing the theta-rhythm in the hippocampal EEG, eliminated rhythmic activity in some cells with weak theta-modulation. Theta-bursts persisted in cells with stable continuous rhythmicity, though its regularity decreased in some of them. Strong reticular or sensory stimulation evoked an increase of burst frequency, involvement of additional septal cells into rhythmic activity and appearance of the theta-rhythm in the hippocampal EEG. Neither anticholinergic, nor cholinomimetic drugs influenced the frequency and basic characteristics of theta-bursts in any condition tested. The anticholinergic drugs have no selective effect upon low-frequency theta-bursts. The septohippocampal connections contain a significant non-cholinergic component. The theoretical concept of the septum as a sole source of the whole frequency band of the theta-rhythm is proposed.     

Levodopa in Parkinsonism: the Effects of Withdrawal of Anticholinergic Drugs

The results are reported of a trial in which 34 patients receiving a stable dose of levodopa for the treatment of idiopathic Parkinsonism, as well as anticholinergic drugs which they had been taking before the introduction of levodopa, underwent withdrawal of their anticholinergic remedies. Withdrawal was gradual over four weeks in 17 patients (group 1) and abrupt in the remaining 17 (group 2).Only 11 out of 34 patients on stable levodopa therapy were able to tolerate withdrawal of anticholinergic drugs for more than eight weeks. The main reasons for the resumption of these remedies were subjective increases in slowness in 20 (59%), tremor in 15 (44%), and recurrence of hypersalivation in 5 (15%). Hypersalivation was the single feature which was most significantly and adversely influenced by anticholinergic withdrawal in patients on levodopa irrespective of whether withdrawal was sudden or gradual. It is suggested that the synergism which seems to exist between anticholinergic remedies and levodopa may be due to inhibition of dopamine inactivation by anticholinergic drugs, thus ensuring continual utilization, or alternatively, to a primary central anticholinergic effect.Objective and more severe subjective deterioration occurred only on sudden withdrawal. Hence we would advise that if for any reason anticholinergic drugs are to be withdrawn in patients receiving a stable dosage of levodopa this must be done slowly. Conversely it would appear from our results that the introduction of anticholinergic drugs in patients treated initially with levodopa is likely to produce additional benefit, particularly when the maximum tolerated dose of levodopa is small.     

Parkinson's disease.

In Parkinson''s disease there is degeneration of neurons in the substantia nigra, with consequent depletion of the neurotransmitter dopamine. The triad of tremor, rigidity and bradykinesia is the clinical hallmark. Drugs currently used for palliative therapy fall into three categories: anticholinergic agents, dopamine precursors (levodopa combined with extracerebral decarboxylase inhibitors) and artificial dopamine agonists. It has been argued, on theoretical grounds, that some drugs slow the progress of Parkinson''s disease, although no firm evidence has supported this. Treatment must be individualized, and more than one type of drug can be given concurrently after a careful build-up in dosage. We review the adverse effects of various drugs and consider new developments such as slow-release preparations, selective D-1 and D-2 agonists and transplants of dopaminergic cells into the brain. The treatment of Parkinson''s disease can be demanding, rewarding and sometimes frustrating, but it remains a most challenging exercise in pharmacotherapy.     

Neuropharmacology of rotifer feeding,oviposition, and anesthesia

Effect of acetylcholine and anticholinergic drugs on feeding, oviposition, and anesthesia in rotifers was investigated. Neurotransmitter as well as antagonist drugs inhibited feeding in Brachionus calyciflorus in a dose-dependent manner. Most antagonist drugs caused an oscillating tachyphylaxis (drug habituation): the drug effect wore off and returned several times within an hour. Acetylcholine inhibited oviposition in Philodina acuticornis, and this effect was antagonized by all groups of anticholinergic drugs. The strongest antagonism was caused by neuromuscular blockers, and thus the cause of oviposition inhibition may be a cloacal sphincter spasm. Acetylcholinesterase inhibitory insecticides also antagonize the acetylcholine effect. Acetylcholine potentiates the anesthetic activity of ionizing local anesthetics (procaine, lidocaine) as well as that of atropine and the beta-adrenergic blocker propranolol. Muscarinic antagonists (atropine, benactyzine) and propranolol caused foot paralysis in B. calyciflorus, which is also potentiated by acetycholine. Further details of these results are given by Nogrady and Keshmirian (1986a, b).     

A Predictive In Vitro Model of the Impact of Drugs with Anticholinergic Properties on Human Neuronal and Astrocytic Systems

The link between off-target anticholinergic effects of medications and acute cognitive impairment in older adults requires urgent investigation. We aimed to determine whether a relevant in vitro model may aid the identification of anticholinergic responses to drugs and the prediction of anticholinergic risk during polypharmacy. In this preliminary study we employed a co-culture of human-derived neurons and astrocytes (NT2.N/A) derived from the NT2 cell line. NT2.N/A cells possess much of the functionality of mature neurons and astrocytes, key cholinergic phenotypic markers and muscarinic acetylcholine receptors (mAChRs). The cholinergic response of NT2 astrocytes to the mAChR agonist oxotremorine was examined using the fluorescent dye fluo-4 to quantitate increases in intracellular calcium [Ca²⁺]i. Inhibition of this response by drugs classified as severe (dicycloverine, amitriptyline), moderate (cyclobenzaprine) and possible (cimetidine) on the Anticholinergic Cognitive Burden (ACB) scale, was examined after exposure to individual and pairs of compounds. Individually, dicycloverine had the most significant effect regarding inhibition of the astrocytic cholinergic response to oxotremorine, followed by amitriptyline then cyclobenzaprine and cimetidine, in agreement with the ACB scale. In combination, dicycloverine with cyclobenzaprine had the most significant effect, followed by dicycloverine with amitriptyline. The order of potency of the drugs in combination frequently disagreed with predicted ACB scores derived from summation of the individual drug scores, suggesting current scales may underestimate the effect of polypharmacy. Overall, this NT2.N/A model may be appropriate for further investigation of adverse anticholinergic effects of multiple medications, in order to inform clinical choices of suitable drug use in the elderly.     

A spin label study of the membrane effect of various psychoactive drugs in human erythrocytes

The effect of psychoactive agents with different clinical actions: three sedative neuroleptics (trifluoperazine, alimemazine tartrate, chlorpromazine), an anticholinergic agent (trihexyphenidyl hydrochloride), two tricyclic antidepressants (imipramine, desipramine) and lithium carbonate on the rotational correlation frequency (V⁺) of the spin label 16NS has been comparatively investigated in whole human erythrocytes. V⁺ was about 40% increased by the three neuroleptics, the anticholinergic agent and the antidepressant molecules at 0.2mM. By contrast, lithium did not induce any significant change in V⁺ at the same concentrations. It can be suggested that the increase in “membrane fluidity”, observed with a wide variety of drugs, is a non specific effect, unrelated to the psychotropic action, that can be ascribed to the amphiphilic properties of the tested drugs.     

Inhibition of inflammatory pain by naloxone and its N methyl quaternary analogue

Naloxone hydrochloride (Nx) and methylnaloxone methylsulfate (MeNx) antagonized the inflammatory pain, but not oedema, produced by intraplantar carrageenan in rats. The liminar effective dose (3 microgram/kg) was the same for the two drugs after intraplantar or subcutaneous injection. The s.c. dose effects curves were, as a whole, similar for the two drugs. The effect was long lasting and stereospecific. The low "analgesic" s.c. doses of Nx were able to antagonize morphine analgesia, those of MeNx were not. The interpretation is difficult; a peripheral action or better the local production of morphinomimetic metabolite(s) might account for most facts.     

Anticonvulsant effects of phencynonate hydrochloride and other anticholinergic drugs in soman poisoning: neurochemical mechanisms

Previous studies have paid little attention to the anticonvulsant effect of anticholinergic drugs that act on both muscarinic (M) and nicotinic (N) receptors during soman-induced seizures. Therefore, with the establishment of a soman-induced seizures model in rats, this study evaluated the efficacy in preventing soman-induced convulsions of two antagonists of both the M and N receptors, phencynonate hydrochloride (PCH) and penehyclidine hydrochloride (8018), which were synthesized by our institute, and of other anticholinergic drugs, and investigated the mechanisms of their antiseizures responses. Male rats, previously prepared with electrodes to record electroencephalographic (EEG) activity, were pretreated with the oxime HI-6 (125 mg kg-1, i.p.) 30 min before they were administered soman (180 microg kg-1, s.c.). All animals developed seizures subsequent to this treatment. Different drugs were given at different times (5, 20 and 40 min after seizures onset) and their anticonvulsant effects were monitored and compared using the two variables, i.e. the dose that could totally control the ongoing seizures, as well as the speed of seizures control. The anticonvulsant effects of atropine, scopolamine and 8018 decreased with the progression of the seizures, and they eventually lost their anticonvulsant activity when the seizures had progressed for 40 min. In contrast, PCH showed good anticonvulsant effectiveness at 5 and 20 min, and especially at 40 min after seizures onset. Of the anticholinergic drugs tested, atropine, scopolamine, and 8018 showed no obvious protection against pentylenetetrazol (PTZ)-induced convulsions or N-methyl-D-aspartate (NMDA)-induced lethality in mice. However, PCH antagonized the PTZ-induced convulsions in a dose-dependant manner with an ED50 of 10.8 mg kg-1, i.p. (range of 7.1-15.2 mg kg-1) and partly blocked the lethal effects of NMDA in mice. PCH also dose-dependently inhibited NMDA-induced injury in rat primary hippocampal neuronal cultures, suggesting a possible neuroprotective action in vivo. In conclusion, our study suggests that the mechanisms of PCH action against soman-induced seizures might differ from those of the M receptor antagonists atropine and scopolamine, and that of the antagonist of both the M and N receptors, 8018. The pharmacological profile of PCH might include anticholinergic and anti-NMDA properties. Compared with the currently recommended anticonvulsant drug diazepam, with known NMDA receptor antagonists such as MK-801 and with conventional anticholinergics such as scopolamine and atropine, the potent anticonvulsant effects of PCH during the entire initial 40 min period of soman poisoning, and its fewer adverse effects, all suggest that PCH might serve as a new type of anticonvulsant for the treatment of seizures induced by soman.     

Muscarinic signalling affects intracellular calcium concentration during the first cell cycle of sea urchin embryos

The existence of a response to acetylcholine (ACh) and cholinomimetic drugs in sea urchin eggs and zygotes was investigated in two sea urchin species: Paracentrotus lividus and Lytechinus pictus. The calcium sensitive fluorescent probe, Fura-2 dextran, was employed to investigate the regulation of cytosolic free calcium concentration ([Ca(2+)](i)) by cholinomimetic drugs in unfertilised and fertilised eggs of both the sea urchin species. Exposure to cholinomimetic agonists/antagonists, either extracellularly or intracellularly, had no effect either on resting [Ca(2+)](i) levels in the unfertilised sea urchin egg, or on the transient [Ca(2+)](i) increase at fertilisation. However, following fertilisation, extracellular application of ACh receptors agonists, such as ACh and carbachol, predominantly muscarinic agonist, but not nicotine, induced a significant increase in [Ca(2+)](i), which was partially inhibited by atropine. As a consequence of exposure after fertilisation to the agonists of ACh receptors, chromatin structure was transiently affected. The hypothesis is proposed that muscarinic receptors may be involved in the (presumably Ca(2+)-dependent) modulation of the nuclear status during the first cell cycles.     

Interactions of novel dopaminergic ligands with D-1 and D-2 dopamine receptors

The interactions of three novel dopaminergic ligands, SKF38393, SKF82526 and SKF83742, with D-1 and D-2 dopamine (DA) receptors have been investigated using radioligand binding techniques and computer modeling procedures. Using the bovine anterior pituitary D-2 DA receptor system, SKF38393 and SKF82526 behave as agonists demonstrating biphasic agonist/3H-antagonist competition curves. For both drugs, the high affinity phase comprised 30% of the total displacement curve. Such findings are atypical as previously tested classical dopamine agonists demonstrated high and low affinity displacement phases in equal proportions. Such behavior exhibited by the SKF agonists may be related to their activity as partial agonists. In contrast, SKF83742 behaves as an antagonist exhibiting homogeneous monophasic competition curves. Similar results are obtained in the rat striatal membrane D-2 DA receptor system. Both SKF38393 and SKF82526 also demonstrate shallow biphasic displacement curves on rat striatal D-1 receptors labeled with 3H-flupentixol whereas SKF83742/3H-flupentixol curves are uniphasic. Of all the ligands, only SKF38393 clearly demonstrates higher affinity for 3H-flupentixol labeled D-1 receptors.     

Lack of correlation between schistosomicidal and anticholinergic properties of hycanthone and related drugs

Visual observation of the motor activity of Schistosoma mansoni kept in vitro showed an increase of activity in the presence of hycanthone (HC). In addition, HC caused a delay in the paralytic effects of carbachol. Similar results were observed in the presence of oxamniquine (OXA). The same pattern of motor activity, however, was shown by HC-resistant worms, by Schistosoma japonicum, and by worms exposed to drug precursors (lucanthone and UK-3883), which are not schistosomicidal in vitro. Other analogs with in vitro killing activity (IA-4 and IA-4 N-oxide) showed minimal anticholinergic effects. The anticholinergic effects of HC and OXA were quickly reversible in vitro and in vivo, whereas their antischistosomal effects are irreversible and delayed. Incubation of schistosomes with high concentrations of carbachol or with anticholinergic drugs failed to compete with the schistosomicidal effects of HC. These results are viewed as contradictory to the hypothesis that HC kills schistosomes by blocking their acetylcholine receptors.     

Ca(2+)-signaling in peritoneal macrophages

Mechanisms of the Ca2+ signal generation and regulation in peritoneal macrophages activated with purinergic agonists (ATP, UTP), as well as endoplasmic Ca(2+)-ATPase inhibitors, were investigated. Using a wide range of drugs affecting the intracellular signaling systems' components, an important role of second messenger systems and other key functional cellular systems in Ca2+ signals regulation in the macrophages, was shown.     

Comparison of three S‐β‐CDs with different degrees of substitution for the chiral separation of 12 drugs in capillary electrophoresis

Three kinds of sulfated β‐cyclodextrin (S‐β‐CD), including a single isomer, heptakis‐6‐sulfato‐β‐cyclodextrin (HS‐β‐CD), degree of substitution (DS) of 7, which was synthesized in our laboratory and another two commercialized randomly substituted mixtures, a sulfated β‐cyclodextrin with DS of 7 to 11, as well as a highly sulfated‐β‐cyclodextrin with DS of 12 to 15, were used for the enantioresolution of 12 drugs (the β‐blockers, phenethylamines, and anticholinergic agents) in capillary electrophoresis. The enantioseparation under varying concentrations of S‐β‐CD and background electrolyte pH were systematically investigated and compared. Based on the experimental results, the effect of the nature of S‐β‐CD and analyte structure on the enantioseparation is discussed.     

5-Methylphenazinium methylsulfate mediates cyclic electron flow and proton gradient dissipation in chromaffin-vesicle membranes

When 5-methylphenazinium methylsulfate and a reductant (ascorbate or NADH) are added together to a suspension of resealed chromaffin-vesicle membranes, the pH gradient (inside acidic) and the membrane potential (inside positive) established by the H(+)-translocating adenosine triphosphatase (ATPase) are rapidly dissipated. Dissipation of the pH gradient may be observed using either the optical probe acridine orange or the weak base methylamine. Dissipation of the membrane potential may be observed using the potential-dependent dye oxonol VI. A reductant and 5-methylphenazinium methylsulfate added in combination will also abolish a K+ diffusion potential across chromaffin-vesicle membranes but not across liposome membranes. 5-Methylphenazinium methylsulfate oxidizes cytochrome b561 in chromaffin-vesicle ghosts. Ascorbate readily reduces cytochrome b561, but reduction of cytochrome b561 by NADH is greatly enhanced in the presence of 5-methylphenazinium methylsulfate. These results are consistent with a mechanism in which proton gradient dissipation (a net efflux of H+) is caused by an influx of electrons through the membrane-protein cytochrome b561 coupled with an efflux of H carried by the reduced species 5-methyl-10-hydrophenazine. Although 5-methylphenazinium has been thought to accumulate within acidic vesicles as a weak base, this accounts for neither proton gradient dissipation nor for intravesicular accumulation of the compound.     

Carga anticolinérgica y delirium en pacientes mayores durante la hospitalización en una unidad de agudos de geriatría

BackgroundThe use of anticholinergic drugs in the elderly has been associated to an increased frequency of delirium. There are different scales for estimating the anticholinergic burden, such as the Anticholinergic Drug Scale (ADS), Anticholinergic Risk Scale (ARS), and Anticholinergic Cognitive Burden (ACB). The aim of the study is to establish the relationship between anticholinergic burden measured by ADS, ARS, and ACB scales and incident or prevalent delirium.MethodsAn ambispective observational study was conducted for 76 days in the acute geriatric unit of a tertiary hospital. All patients over 80 years-old were included, except re-admissions or those subjected to palliative care. The data collected included sex, age, chronic medication and any recent changes, recent drugs prescribed prior to an episode of delirium, chronic kidney disease, diabetes mellitus, dementia, visual and auditory impairment, and their combination as sensory impairment, previous falls, stroke, brain tumour, and incident and prevalent delirium.ResultsA total of 72 patients were included. Incident delirium was detected in 8.1% of the patients, and prevalent delirium in 40.9%. A statistically significant association was established between anticholinergic drugs and the incident delirium measured by the ARS scale (P=.017). None of the scales was able to establish a significant association with prevalent delirium.ConclusionThe ARS scale was related to new episodes of delirium. All scales were insufficient when it came to establishing an association with prevalent delirium.