Cholinolytic Agents Research Articles

Prevention of organophosphate intoxication with presynaptic cholinergic blockers

In Vivo cardiovascular neuromuscular preparation of rats was used to study the prophylaxis and mechanism of diisopropyl fluorophosphate (DFP) intoxication by presynaptic cholinolytic agents (ganglionic blocking agents), including hexamethonium, trimethaphan and mecamylamine. The lethal action of DFP was partially or completely prevented by pretreatment of rats with hexamethonium (10 mg/kg), trimethaphan (80 mg/kg) and mecamylamine (30 mg/kg). Combined use of these drugs with 2-PAM (100 mg/kg) improved further the prophylaxis of DFP lethality. The mechanism of prophylaxis could be due to the reduction of acetylcholine turnover and accumulation at the synaptic cleft as hemicholinium prevented the DFP intoxication efficiently. In all cases, DFP caused cardiovascular suppression before neuromuscular blockade indicating that the cardiovascular system is much more sensitive than the neuromuscular junction to DFP intoxication.

Pilocarpine-Induced Convulsions in Rats: Evidence for Muscarinic Receptor-Mediated Activation of Locus Coeruleus and Norepinephrine Release in Cholinolytic Seizure Development

We recently reported that systemic administration of the anticholinesterase, soman, caused rapid depletion of forebrain norepinephrine (NE) in convulsive but not in nonconvulsive rats (18). As neurons in nucleus locus coeruleus (LC) provide the bulk of NE innervation to most of the forebrain and the sole source of NE input to the cortex and the olfactory bulb, soman-induced NE depletion was hypothesized to result from activation of LC neurons. This activation was thought to be due to inhibition of acetylcholinesterase by soman, leading to rapid, sustained accumulation of acetylcholine in LC, causing these cells to fire at a high sustained rate. Support for this hypothesis was provided by neurophysiological findings (21) showing that: (i) Systemic administration of soman in anesthetized rats caused a sustained, fivefold increase in the mean firing rate of LC neurons and (ii) microinjections of soman directly into LC caused a similar increase in the firing rate of LC neurons (21). Soman-induced activation of LC occurred prior to and even in the absence of seizures. As systemic administration of the muscarinic receptor antagonist, scopolamine, rapidly and completely reversed soman-induced activation of LC, it was further hypothesized that activation of LC neurons following soman administration is due to muscarinic receptor stimulation. The rapid release of NE by cholinolytic agents, thus, may play an important role in the initiation and/or maintenance of convulsions. To further test the hypothesis that NE release in soman-intoxicated rats is due to muscarinic activation of LC, we have investigated the effects of the muscarinic receptor agonist, pilocarpine, on NE release and LC discharge. In one set of experiments, rats were injected with a periconvulsive dose of pilocarpine (300 mg/kg, ip); both convulsive and nonconvulsive rats were sacrificed between 1 and 96 h and monoamine levels in the rostral forebrain and olfactory bulb were determined by HPLC with electrochemical detection. NE levels declined substantially only in convulsive rats; forebrain NE levels in convulsive rats rapidly decreased to 50% of control levels at 1 h and to 37% of controls level between 2 and 4 h. The time course and magnitude of these changes were similar to those observed following soman administration in our previous study (18). Recovery of forebrain NE began at 8 h and was complete by 96 h following pilocarpine administration. Neither dopamine (DA) nor serotonin (5-HT) levels were changed in the forebrain and olfactory bulb of either convulsive or nonconvulsive rats. However, both convulsive and nonconvulsive rats exhibited similar increases at 1-4 h in the levels of DA metabolites (3,4-dihydroxyphenylacetic acid, homovanillic acid) and the major metabolite of 5-HT, 5-hydroxyindoleacetic acid. In a second set of experiments, we examined the effect of systemic and local administration of pilocarpine on the firing rate LC neurons in anesthetized rats. Systemic administration of pilocarpine caused a sustained, fivefold increase in mean LC neurons firing rate. Microinjections of pilocarpine directly into LC caused a similar increase in the firing rate of LC neurons. Thus, the increase in LC discharge rate produced by pilocarpine was nearly identical to that of soman. The effects of systemically and intracoerulearly administered pilocarpine on LC discharge were reversed by the muscarinic receptor antagonist, scopolamine. The present neurochemical and electrophysiological results thus support the hypothesis that NE depletion in convulsive rats treated with soman is the result of muscarinic receptor-mediated cholinergic activation of LC neurons.

Salivation from the denervated human parotid gland induced by pirenzepine and telenzepine

In the denervated human parotid gland the non-classical cholinolytic agents pirenzepine and telenzepine induce a similar paradoxical salivatory response to that of atropine, scopolamine and metacine.

Modification of selective adsorption of muscarinic antagonists on brain membranes during chlorophos poisoning

Using radioligand assay it was demonstrated that chlorophos intoxication produced inhibiting effect on the kinetics of membrane binding of 3H3-quinuclidinylbenzilate and 14C-cyclosil in the brain. Cholinesterase reactivator dipyroxime was shown to induce normalization of the cyclosyl specific binding kinetics. It seems to be justified to propose that cooperative action of cholinolytic agents and cholinesterase reactivator at the level of m-cholinoreceptors in the course of intoxication may be one of the mechanisms of the potentiation of therapeutic effects of these drugs.

The action of cholinomimetic and cholinolytic agents, hemicholinium-3 and α- and β-bungarotoxin on the body wall muscle of the earthworm, lumbricus terrestris

Strips of muscle, approximately 12 segments in length, were prepared from the body wall of the earthworm, Lumbricus terrestris, from which the nerve cord and viscera had been removed. Contractions to electrical stimulation and acetylcholine agonists were recorded using an isometric transducer. A range of nicotinic and muscarinic agonists and antagonists were tested on this preparation and the results indicate that the acetylcholine receptor on this muscle cannot be classified as either nicotinic or muscarinic. Hemicholinium-3 abolished electrically induced muscle twitches at concentrations which had no effect on the acetylcholine response. α-Bungarotoxin blocked the responses to both electrical stimulation and acetylcholine while β-bungarotoxin blocked the contractions induced by electrical stimulation but potentiated the acetylcholine contraction.

Hyperactivity induced by injection of dopamine into the accumbens nucleus: actions and interactions of neuroleptic, cholinomimetic and cholinolytic agents.

Abstract The present studies determined whether the neuroleptic ability to antagonize hyperactivity caused by intra-accumbens injection of dopamine in the rat could be mimicked by cholinomimetics and reversed by cholinolytics. The dopamine response was antagonized by eserine (2.5 and 5 μg) and arecoline (10–40 μg), but methacholine (10–40 μg), acetylcholine (10–100 μg), carbachol (5 μg) and nicotine (10–40 μg) were either inactive or their effects were non-specific. The eserine response (5 μg) was reversed by peripherally administered atropine (5 mg/kg i.p.) but not by the nicotinic antagonist mecamylamine (5–40 μg). Systemically administered haloperidol (0.2–0.8 mg/kg i.p.) also reduced or abolished the dopamine response but this effect was not reversed by mecamylamine (10 mg/kg i.p.) or by atropine (1–5 mg/kg i.p.), procyclidine (10 mg/kg i.p.), orphenadrine (10 mg/kg i.p.) and dexetimide (1 mg/kg i.p.). These cholinolytics alone failed to modify the dopamine-induced hyperactivity. Thus, cholinomimetics may mimic the ability of neuroleptics to antagonize hyperactivity induced by dopamine from the nucleus accumbens, and the evidence would favour an interaction with the dopamine response via muscarinic cholinergic mechanisms, although a nicotinic involvement cannot be excluded. However, the results suggest that an enhanced cerebral cholinergic activity may not be essential for the neuroleptic inhibitory action, either in the nucleus accumbens or elsewhere.

History of Surgical Correction of Male Urinary Incontinence

SUMMARY For more detailed descriptions of the various operations for incontinence, the reader is referred to the extensive references provided at the end of this article. In this issue of Urologic Clinics, we have asked the principal proponents of operations currently employed to present their techniques and results, since each of the authors has a novel procedure and an extensive experience. Thus, Scott presents his up-to-date views on the use of the artificial genitourinary sphincter, Politano reports his results with Teflon injection and modifications of his original technique, Rosen gives the description of his prosthesis and the results in his hands, and I update our experience with the silastic prosthesis to compress the urethra in the perineum. The following is a classification and summary of treatment for male urinary incontinence: I. Nonsurgical A. Expectant, 9 months to 1 year B. Training C. Pharmacological 1. α-adreriergic simulators 2. Cholinolytic agents D. Electrical stimulation (plus training) (Hopkinson and Lightwood, 1967) E. Injection 1. Sclerosing fluids (Sachse, 1963) 2. Paraffin (Quackels, 1955) 3. Supportive material – Teflon (Politano, 1973) II. Surgical A. “Surrogate sphincter” formation 1. Abdominal muscle and fascial slings a. Pyramidalis and/or rectus fascia and muscle (Goebell, 1910) (Stoeckel, 1917) (Frangenheim, 1914) (Millin, 1969) (Cooney and Horton, 1951) 2. Gracilis muscle slings a. Gracilis muscle (Deming, 1926) (Player and Callender, 1927) 3. Fascia lata strips (Boer and Ivanovici, 1974) 4. Perineal muscles a. Ischiocavernosus (Lowsley, 1936) b. Levator ani (Squier, 1911) c. External sphincter ani (Verges-Plaque, 1951) (Mathisen, 1970) 5. Bladder flaps a. Tube (Tanagho, Smith, Meyers, and Fisher, 1969) b. Spinal (Flocks and BoIdus, 1973) 6. Prosthetic devices a. External (Foley, 1947) b. Implanted (Scott, 1973) (Scott, 1978) (Rosen, 1978) (Swenson, 1978) B. Vesicourethral suspension and angulation 1. Kelly, 1928 2. Marshall and Marchetti, 1949 C. Posterior urethral lengthening 1. Young and Dees, 1919 2. Thompson, 1961 3. Leadbetter, 1967 D. Urethral plication and twists 1. Young, 1908 2. Beneventi, 1966 3. Petersen, 1967 E. Urethral compression – passive 1. Berry, 1961 (Acrylic; silastic) 2. Girgis and Veenema, 1965 (Collagen) 3. Hinman and Schmaelze, 1978 (Autologous rib) 4. Millin, 1969 (Fascia lata) 5. Kaufman I (Crural cross, 1970) II (Crural approximation, 1972) III (Silicone-gel prosthesis, SGP, 1973) 6. Puigvert, 1971 (Crural approximation) 7. Salcedo, 1972 (Marlex) 8. Yarbrough, 1975 (SGP and Marlex) F. Electrical stimulation (with electronic implants) 1. Caldwell, 1963 2. Merrill, 1971 G. Urinary diversion 1. Ileal conduit 2. Colon conduit 3. Ureterosigmoidostomy 4. Cutaneous ureterostomy 5. Vesicostomy and BN closure 6. Nephrostorny

Effect of cholinolytic and adrenoblocking agents on resistance of rat erythrocytes to hypoosmotic hemolysis

The effect of central cholinolytics and adrenoblockers on hemolysis of rat erythrocytes in hypoosmotic buffer was studied in vitro. At pH 7.4 and in a concentration of 10−4 M, hemolysis was prevented to the greatest degree by the central nicotinic (n) cholinolytics ethyldiphacil, diphacil1), pediphen2), tropacin3), and the β-adrenoblocker propranolol. Erythrocytes were protected against hemolysis to a lesser degree by the central muscarinic (m) cholinolytics amizil4) and glypin5) and the α-adrenoblockers pyrroxan6), sympatholytin7), and phentolamine. The antihemolytic effect of the drugs reached a maximum in the course of 30 min and continued for several hours. A lower level of ionization of the drugs containing a tertiary nitrogen atom in their molecule was shown to correspond to greater protection of the erythrocytes against hemolysis. the prevention of hypoosmotic hemolysis is evidence of stabilization of the erythrocyte membrane by the substances studied. The possibility of stabilization of membrane formations not containing synaptic contacts must be taken into account when considering the mechanism of action of central n-cholinolytics and β-adrenoblockers.

The action of cholinergic antagonists on the effect of acetylcholine, nicotine and benzoylcholine applied iontophoretically onto two identified neurones in the brain of helix aspersa

1. Intracellular recordings were made from 2 identified neurones in the brain of Helix aspersa. Cell E4 is inhibited by acetylcholine while cell F1 is excited by acetylcholine. 2. Thirteen cholinolytic agents were tested for their blocking actions against iontophoretically-applied acetylcholine on the 2 cells. The compounds examined were strychnine, scopolamine, atropine, tubocurarine, pancuronium, gallamine, hexamethonium, pentolinium, mecamylamine, benzoquinonium, decamethonium, suxamethonium and benzolcholine. All the compounds were at least partial antagonists on cell E4 while only three, i.e. scopolamine, decamethonium and suxamethonium, did not block the cholinergic receptors of cell F1. 3. Four cholinolytics were further tested as antagonists against iontophoretically-applied nicotine and benzoylcholine; these were atropine, strychnine, tubocurarine and hexamethonium. The only compound which did not block the actions of nicotine and benzoylcholine on both cells was strychnine which had no blocking action against benzoylcholine on cell F1.

Receptor mechanisms in fish chromatophores—IV. Effects of melatonin and related substances on dermal and epidermal melanophores of the siluroid, Parasilurus asotus

1. Melatonin was extremely effective in inducing melanosome aggregation in both dermal and epidermal melanophores of the siluroid catfish, Parasilurus asotus. 2. While precursors of melatonin, 5-hydroxytryptamine and N-acetyl-5-hydroxytryptamine, were without effects, its possible metabolites, 5-methoxytryptamine and 6-hydroxymelatonin, showed moderate action to aggregate the pigment. 3. Muscarinic cholinolytic agents, which were complete blockers of the melanin-aggregating nervous effect, had no influence in melatonin action. 4. Also, neither alpha nor beta adrenolytic agents showed an inhibitory effect on the melatonin action. 5. The conclusion is that the melanin-aggregating action of melatonin may be mediated by its specific receptors in the melanophores, and that the 5-methoxy group on the indole ring may be essential for its action.

Influence of metiamide and atropine on pepsinogen secretion in the conscious rat.

Activity of peptic cells is influenced directly by cholinolytic or cholinergic agents. Histamine H2-antagonists influence the activity of the chief cells through changes of acidity of gastric juice.

Modification of evoked responses in the caudate nucleus by cholinergic agents

In order to further define cholinergic mechanisms in basal ganglia structures, macroelectrodes were placed into the caudate nucleus, globus pallidus, substantia nigra, and certain thalamic nuclei of paralyzed unanaesthetized cats. The effects of systemically administered cholinomimetic and cholinolytic agents on evoked responses generated between connecting structures were studied. Physostigmine sulphate and the direct muscarinic stimulants arecoline and oxotremorine but not pilocarpine depressed intercaudate and intracaudate responses, while atropine sulphate caused enhancement of these responses and reversed the effect of cholinomimetic drugs. Nicotinic drugs were without effect. Cholinergic drugs had no effect on caudate afferent responses or on any other basal ganglia evoked potentials. These findings implicate the caudate interneurone as the source of basal ganglia cholinergic activity.

The cholinergic rigidity

NUMEROUS accounts have been given on the influence on spinal reflex activity of acetylcholine and cholinesterase inhibitors under different experimental conditions and in various animal species (cf. Machne and Unna. 1963). However, when scrutinizing the early literature, it is hard to obtain satisfying informations concerning a state of rigidity produced by acetylcholine or drugs which facilitate cholinergic transmission. This is all the more astonishing because it was known long ago that cholinolytic agents, especially atropine. exert beneficial effects on the Parkinson syndrome, including rigidity. Moreover, cholinomimetic drugs have been described to intensify not only tremor, but also rigidity in Parkinson patients (Zucker, 1925; Marinesco and Bourgignon, 1927; Duvoisin, 1967). In 1966. Arvidsson et al. reported on experiments performed with physostigmine on rat spinal motoneurons. The study was prompted by the idea that an imbalance between cholinergic and monoaminergic (especially dopaminergic) activities in the brain in favor of cholinergic dominance leads to a Parkinson-like state (Barbeau, 1962). Physostigmine is a cholinesterase inhibitor which readily penetrates the blood-brain barrier. Systemic application of the drug to preparations with an intact neuraxis induced Rigidity may be demonstrated by the appearance of tonic activity in the electromyogram during sustained muscle stretch (Fig. 6).

An electrophysiological study of the effects of d-tubocurarine, atropine, and α-bungarotoxin on the cholinergic receptor in innervated and chronically denervated mammalian skeletal muscles

An electrophysiological study of the action of d-tubocurarine ( d-TC), atropine, and α-bungarotoxin (BuTX) was made on the innervated and chronically denervated diaphragm and soleus muscles of the rat and mouse. All three drugs were able to block endplate potentials of innervated muscles as well as acetylcholine (ACh) sensitivity of chronically denervated muscles. The effects of atropine and d-TC were fully reversed upon washing with Ringer's solution, white the effects of BuTX were only partially reversed. The reversibility of BuTX was more evident at extrajunctional areas in chronically denervated muscles than at the innervated endplate region, but in both cases only a fraction of the normal response could be detected after intensive washing for at least 2 hr. The blockade of ACh sensitivity in chronically denervated muscles required a concentration of d-TC 10-fold higher than that necessary to block the endplate potentials of innervated muscles. BuTX and d-TC did not affect the ionic permeabilities of the muscle fiber during an action potential while atropine decreased both Na + and K + conductances, the magnitude of the effect being dependent on the frequency of stimulation. At the endplate region, d-TC was much more effective than atropine in protecting against the irreversible effect of BuTX. In the chronically denervated preparation, however, neither of the two drugs effectively protected against BuTX. It is concluded that in terms of their reactivities to cholinolytic agents, the extrajunctional receptors induced by chronic denervation of skeletal muscles are qualitatively similar to those found at endplate regions of normal muscles, but that they exhibit differences in their quantitative interaction with different cholinolytic agents. The data further indicate that atropine interacts with the ionic conductance modulator unit associated with the cholinergic receptor, rather than with the ACh receptor itself.

The convulsant effect of topically applied atropine

Atropine is a potent convulsant when applied topically to the cortex, producing long-lasting large amplitude spikes. This study was designed to dilineate further this convulsant action and to determine whether it is related to the cholinolytic or local anesthetic properties of atropine. We studied therefore the effects of topically applied aatropine, homatropine, methylatropine, scopolamine, acetylcholine and procaine in a series of cats prepared with high cervical transection. Atropine, homatropine and methylatropine produced prominent spike activity in the electrocorticogram within minutes after the application of a 1 solution, but scopolamine and procaine did not do so in strengths of up to 40% and 10%, respectively. All the cholinolytic agents used, however, had identical effects on the action of topically applied acetylcholine, in that they raised the threshold for the production of the well known acetylcholine-induced paroxysms, and they modified these paroxysms so that they came to resemble atropine-induced spikes. These findings suggest that the convulsant property of atropine is independent of the hitherto established actions of this drug, namely as a muscarinic antagonist or as a local anesthetic agent.

Effects of cholinolytic agents on behavior following development of tolerance to low cholinesterase activity.

The development of tolerance during periods of chronically low levels of cholinesterase (ChE) induced by administration of diisopropyl fluorophosphate (DFP) is evidenced in systematic changes in behavioral variables. The present experiment was designed to study the biochemical mechanism(s) involved by challenging tolerant and control subjects with pharmacological agents known to affect the cholinergic system: the cholinolytics, atropine and methylatropine. Measures of the free operant behavior showed tolerance to have developed by the 9th injection of DFP, after which the challenge series began. Clear differences were apparent between the effects of the cholinolytic agents on the tolerant and control groups. Dose-response curves for both groups showed similar trends of decreasing performance with increasing dose level until a critical point was reached. With further increases in dose, there was a complete absence of responding in the majority of tolerant subjects, while control animals continued to perform at about 40 per cent normal. The fact that effects of the methylatropine challenge were not significantly different in tolerant and control subjects implies that the biochemical process(es) of tolerance had a major central component.

The effect of physostigmine and tetrabenazine on spinal motor control and its inhibition by drugs which influence reserpine rigidity.

The effect of monoaminergic (DOPA, metamphetamine, propylhexedrine) and cholinolytic agents (atropine, biperiden, caramiphen, trihexyphenidyl) on spinal motor control disturbed by physostigmine and tetrabenazine was studied in the rat. In addition the anticonvulsant agent phenytoin was included in the investigation. Physostigmine and tetrabenazine produced rigidity, increased α reflex discharge, shortened the latency of α reflex discharge and decreased γ reflex discharge. Rigidity as well as the action of physostigmine and tetrabenazine on α motor activity were inhibited by the drugs. The results are in accordance with the hypothesis that parkinsonlike rigidity in the rat results from hyperactivity of the α motor system, which is due to an imbalance between monoaminergic and cholinergic mechanisms in the brain.

Inhibition of the effect of reserpine on motor control by drugs which influence reserpine rigidity.

The effect of monoaminergic (DOPA, metamphetamine, propylhexedrine) and cholinolytic agents (atropine, biperiden, caramiphen, trihexyphenidyl) on α and γ reflex discharge from the spinal cord was studied in the rat. For comparison, the anticonvulsant phenytoin was included in the investigation. All drugs antagonized the action of a high dose of reserpine on motor control by reducing the increased α and increasing the diminished γ reflex activity. The latency of α reflex discharge shortened by reserpine was increased by the drugs. The results provide further support of the view that disturbance of motor control caused by reserpine in the rat derives from an imbalance between monoaminergic and cholinergic systems in the brain.

Cholinergic mechanisms in the caudate nucleus.

1. Acetylcholine (ACh), and a number of cholinomimetic and cholinolytic agents, have been applied to single neurones of the caudate nucleus, and the effects compared with those produced by stimulation of nucleus ventralis anterior thalami (VA).2. Neurones responding by excitation following ACh and VA stimulation, and others depressed by both ACh and VA stimulation have been observed. The two types of cell are located in different regions of the nucleus.3. Both types of ACh effect, and the responses to VA stimulation, are prevented by atropine.4. Taken with the earlier observation that the release of ACh from the caudate can be enhanced by VA stimulation, it has been suggested that the present results indicate a final cholinergic link in the pathway from VA to caudate.

Sensitizing and desensitizing influence of atropine, bete, and amysyl on the spasmolytic activity of pentaphene and tropacine

A study was made of the combined effects of a number of cholinolytic agents, comprising: atropine, amysyl, BETE (chlorhydrate of the tropine ester of benzylic acid), pentaphene, tropacine, and scopolamine. Substances were given in pairs. Nicotine hyperkinesis in mice was used as an experimental model. The action of the substances was evaluated by Loewe's method (1928). The results showed that atropine and pentaphene give together caused a rise in the effectiveness of the latter in preventing tremor from nicotine (atropine “sensitizes” to pentaphene). No such effect was observed when pentaphene was given together with such preparations as BETE and amysyl. Atropine potentiated tropacine; conversely tropacine reduced the effect of amysyl (“desensitization”). Under these conditions, BETE did not significantly influence tropacine action. The results obtained indicate the very diverse actions of these drugs in producing “sensitiziation,” “desensitization,” etc. when given together to animals in which nicotine hyperkinesis had been induced.