piperidines and telenzepine

Although the molecular machinery and mechanism of cell secretion in acinar cells of the exocrine pancreas is well documented and clear, only recently has the pharmacophysiology of pancreatic exocrine secretion come to light. Therefore, we focus in this article on the current understanding of the pharmacophysiology of pancreatic exocrine secretion. The pancreatic secretory response to ingestion of a meal is mediated via a complex interplay of neural, humoral and paracrine mediators. A major role in the control of the intestinal phase of pancreatic secretion is attributed to vago-vagal enteropancreatic reflexes. In the scheme of this control mechanism, afferents originating in the duodenal mucosa, and efferents mediating central input on the pancreatic ganglia, activate intrapancreatic postganglionic neurons. Experiments utilizing specific receptor antagonists demonstrate the involvement of both muscarinic M1 and M3 receptors expressed in pancreatic acinar cells. Cholecystokinin (CCK), originally implicated in the humoral secretion of pancreatic enzymes, through a direct action on acinar CCK receptors, is also essential to the enteropancreatic reflex mechanism. CCK stimulation of the exocrine pancreatic secretion through excitation of sensory afferents of the enteropancreatic reflexes, is a paracrine mode of CCK action, and is probably the only one in humans and the predominant one in rats. In dogs, however, CCK acts on the pancreas via both the humoral and a paracrine route. More recent experiments suggest further possible sites of CCK action. Additionally, at the brain stem, vago-vagal enteropancreatic reflexes may be modulated by input from higher brain centres, particularly the hypothalamic-cholinergic system in the tonic stimulation of preganglionic neurons of the dorsal motor nucleus of the vagus projecting into the pancreas.

Topics: Animals; Cholecystokinin; Dogs; Guinea Pigs; Humans; Mice; Pancreas, Exocrine; Piperidines; Pirenzepine; Rats; Receptor, Muscarinic M1; Receptor, Muscarinic M3; Receptors, Cholecystokinin; Reflex; Vagus Nerve

Albeit time-consuming, the most rigorous method of classification of receptor subtypes is the determination of pA2 values. However, this methodology requires the knowledge of absolute concentrations of both agonists and antagonists--something that may not necessarily be calculable under certain experimental conditions. Wolfgang Kromer offers a different method for classification using antagonists which is not dependent on absolute affinities, and which has the additional advantage of speed.

Topics: Alkaloids; Binding, Competitive; Furans; Muscarinic Antagonists; Naphthalenes; Piperidines; Pirenzepine; Receptors, Muscarinic

Topics: Animals; Animals, Newborn; Behavior, Animal; Carbachol; Chickens; Disease Models, Animal; Eating; Injections, Intraventricular; Muscarinic Agonists; Muscarinic Antagonists; Piperidines; Pirenzepine; Receptor, Muscarinic M1; Receptor, Muscarinic M3

Galantamine, a weak acetylcholine esterase (AChE) inhibitor and allosteric potentiator of nicotinic ACh receptors (nAChRs), improves apomorphine-induced deficits in prepulse inhibition (PPI), sensory information-processing deficits, via a nAChR-independent mechanism. The present study examined the role of muscarinic ACh receptors (mAChRs) in the effect of galantamine, and studied the mechanism of galantamine-induced increases in prefrontal ACh levels in mice.. Apomorphine (1 mg kg(-1)) was administered to male ddY mice (9-10 weeks old) to create a PPI deficit model. Extracellular ACh concentrations in the prefrontal cortex were measured by in vivo microdialysis.. Galantamine- and donepezil-mediated improvements in apomorphine-induced PPI deficits were blocked by the preferential M(1) mAChR antagonist telenzepine. The mAChR agonist oxotremorine also improved apomorphine-induced PPI deficits. Galantamine, like donepezil, increased extracellular ACh concentrations in the prefrontal cortex. Galantamine-induced increases in prefrontal ACh levels were partially blocked by the dopamine D(1) receptor antagonist SCH23390, but not by antagonists of mAChRs (telenzepine) and nAChRs (mecamylamine). Galantamine increased dopamine, but not 5-HT, release in the prefrontal cortex.. Galantamine improves apomorphine-induced PPI deficits by stimulating mAChRs through increasing brain ACh levels via a dopamine D(1) receptor-dependent mechanism and AChE inhibition.

Topics: Acetylcholine; Acoustic Stimulation; Animals; Animals, Outbred Strains; Apomorphine; Behavior, Animal; Benzazepines; Cholinesterase Inhibitors; Donepezil; Dopamine; Dopamine Agonists; Dopamine Antagonists; Dose-Response Relationship, Drug; Drug Interactions; Galantamine; Indans; Inhibition, Psychological; Male; Mecamylamine; Mice; Microdialysis; Muscarinic Agonists; Muscarinic Antagonists; Nicotinic Antagonists; Oxotremorine; Piperidines; Pirenzepine; Prefrontal Cortex; Receptors, Muscarinic; Reflex, Startle; Serotonin

Acetylcholine may play a role in cell activation and airway inflammation. We evaluated the levels of both mRNA and protein of muscarinic M(1), M(2), M(3) receptors in human bronchial epithelial cell line (16HBE). 16HBE cells were also stimulated with acetylcholine and extracellular signal-regulated kinase1/2 (ERK1/2) and NFkB pathway activation as well as the IL-8 release was assessed in the presence or absence of the inhibitor of Protein-kinase (PKC) (GF109203X), of the inhibitor of mitogenic activated protein-kinase kinase (MAPKK) (PDO9805), of the inhibitor of kinaseB-alpha phosphorilation (pIkBalpha) (BAY11-7082), and of muscarinic receptor antagonists tiotropium bromide, 4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), telenzepine, gallamine. Additionally, we tested the IL-8-mediated neutrophil chemotactic activity of 16HBE supernatants stimulated with acetylcholine in the presence or absence of tiotropium. 16HBE cells expressed both protein and mRNA for muscarinic M(3), M(2) and M(1) receptors with levels of muscarinic M(3) receptor>muscarinic M(1) receptor>muscarinic M(2) receptor. Acetylcholine (10 microM) significantly stimulated ERK1/2 and NFkB activation as well as IL-8 release in 16HBE cells when compared to basal values. Furthermore, while the use of tiotropium, 4-DAMP, GF109203X, PDO98059, BAY11-7082 completely abolished these events, the use of telenzepine and gallamine were only partially able to downregulate these effects. Additionally, acetylcholine-mediated IL-8 release from 16HBE cells significantly increased chemotaxis toward neutrophils and this effect was blocked by tiotropium. In conclusion, acetylcholine activates the release of IL-8 from 16HBE involving PKC, ERK1/2 and NFkB pathways via muscarinic receptors, suggesting that it is likely to contribute to IL-8 related neutrophilic inflammatory disorders in the airway. Thus, muscarinic antagonists may contribute to control inflammatory processes in airway diseases.

Topics: Acetylcholine; Bronchi; Cell Line, Transformed; Chemotaxis, Leukocyte; Epithelial Cells; Flavonoids; Gallamine Triethiodide; Humans; Indoles; Interleukin-8; Maleimides; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Muscarinic Antagonists; Neutrophils; NF-kappa B; Nitriles; Piperidines; Pirenzepine; Protein Kinase C; Receptors, Muscarinic; RNA, Messenger; Scopolamine Derivatives; Sulfones; Tiotropium Bromide

The role of four muscarinic receptor subtypes M1, M2, M3 and M4 which have been characterized pharmacologically was examined in motility control of isolated rat gastric fundus. Acetylcholine produced concentration-dependent tonic contraction of isolated rat fundus (EC50 = 9.64 +/- 0.14 x 10(-8)M). These contractions were concentration-dependently antagonized by atropine (KB = 2.45 x 10(-11)M), M1 selective blockers telenzepine (KB = 6.64 x 10(-11)M) and pirenzepine (KB = 2.3 x 10(-8)M), and hexocyclium (KB = 2.82 x 10(-10)M). M3-selective blocker p-fluoro-hexahydro-sila-difenidol (pFHHSiD) was a less potent antagonist (KB = 2.3 x 10(-8)M), while M2 and M4-selective methoctramine produced only weak blockade of tonic contractions caused by acetylcholine (KB = 4.68 x 10(-6)M). These results suggest that only M1 and M3 muscarinic receptors have functional roles in motility control of rat gastric fundus, M1 receptors being more important.

Topics: Acetylcholine; Animals; Atropine; Diamines; Female; Gastric Fundus; Gastrointestinal Motility; Male; Muscarinic Antagonists; Piperazines; Piperidines; Pirenzepine; Rats; Rats, Wistar; Receptors, Muscarinic

The green mamba (Dendroaspis angusticeps) "muscarinic toxin', MT1, was radioiodinated by the chloramine T method. 125I-MT1 labelled the muscarinic M1 receptor subtype with a very good selectivity in rat brain. It had no preference for the receptor states with high or low affinity for agonists, and was not affected by Gpp(NH)p addition to the incubation medium. The 125I-MT1 binding was reversible, with a half life of 45 min at 25 degrees C. The effect of competitive and allosteric muscarinic antagonists on 125I-MT1 binding and dissociation can be rationalized by assuming that the radioiodinated toxin is able to label the muscarinic (acetylcholine) binding site.

Topics: Alkaloids; Animals; Atropine; Binding, Competitive; Brain; Carbachol; Elapid Venoms; Furans; Gallamine Triethiodide; In Vitro Techniques; Iodine Radioisotopes; Isotope Labeling; Kinetics; Muscarinic Agonists; Muscarinic Antagonists; Naphthalenes; Oxotremorine; Parasympatholytics; Pilocarpine; Piperidines; Pirenzepine; Protein Binding; Rats; Receptor, Muscarinic M1; Receptors, Muscarinic; Synaptic Membranes; Tubocurarine

1. Muscarinic receptor subtypes mediating neurogenic mucus secretion in ferret trachea were characterized in vitro and in vivo using 35SO4 as a label for secreted mucus, and the muscarinic receptor antagonists telenzepine for the M1 receptor subtype, methoctramine for the M2 subtype and 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP) for the M3 receptor. We also performed receptor binding and mapping studies. 2. Each muscarinic antagonist displaced [N-methyl-3H]scopolamine binding with high-affinity binding constant (KH) values of 1.9, 2.7 and 5.0 nM for telenzepine, methoctramine and 4-DAMP, respectively. Muscarinic M1 and M3 receptors localized to submucosal glands, whereas M2 receptors did not. 3. In vitro, electrical stimulation (50 V, 10 Hz, 0.5 ms for 5 min) increased 35SO4 output by 160%. Telenzepine did not inhibit the neurogenic secretory response at concentrations two-or twentyfold its KH value, nor did it inhibit secretion induced by acetylcholine (ACh). 4-DAMP inhibited neurogenic secretion by 80 and 95%, respectively, at concentrations two-and twentyfold its KH value, and also inhibited ACh-induced secretion. Methoctramine potentiated neurogenic secretion induced at 2.5 Hz (50 V, 0.5 ms for 5 min) in a dose-related (5.4-100 nM) manner with increases of 33-451% above electrically stimulated values. Methoctramine did not potentiate secretion induced at 10 Hz and did not have any effect on ACh-induced secretion. 4. In vivo, vagal stimulation (10 V, 10 Hz, 2 ms for 8 min) increased output of 35SO4 by approximately 120%. Telenzepine had no significant effect on neurogenic secretion. Methoctramine approximately doubled the stimulated response, whereas 4-DAMP abolished the stimulated secretory response. 5. We conclude that in ferret trachea, cholinergic nerve stimulation increases mucus secretion via muscarinic M3 receptors on the submucosal glands. The magnitude of the secretory response is regulated by neuronal M2 muscarinic receptors. The muscarinic M1 receptors localized to the submucosal glands do not appear to be involved with mucus secretion.

Topics: Animals; Diamines; Electric Stimulation; Ferrets; In Vitro Techniques; Male; Mucus; Muscarinic Antagonists; Muscle, Smooth; Piperidines; Pirenzepine; Quinuclidinyl Benzilate; Radioligand Assay; Receptors, Muscarinic; Scopolamine; Sulfates; Sulfur Radioisotopes; Trachea; Tritium

We have used the pilocarpine-induced seizure model in mice and i.c.v. injection of subtype-specific receptor antagonists to investigate the muscarinic receptor subtype specificity of cholinergically-activated seizures. The rank order potencies of antagonists for inhibition of pilocarpine-induced seizures are atropine = telenzepine > 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine (4-DAMP) > pirenzepine with ID50's of 8.6, 12.0, 29.9, and 83.0 nmol/mouse, respectively. The M3-specific antagonists hexahydrosila-difenidol and its p-fluoro analog showed no effect on pilocarpine-induced seizures. The M2-specific antagonists gallamine and methoctramine cause seizures in mice in the absence of a pilocarpine injection. These seizures could be inhibited by coinjection of methoctramine with the M1-specific antagonist, pirenzepine. These data suggest a role of muscarinic M1 receptors in mediating pilocarpine-induced seizures and a role of the muscarinic M2 receptors in modulating neuronal activity.

Topics: Animals; Atropine; Cerebral Ventricles; Injections, Intraventricular; Male; Mice; Parasympatholytics; Pilocarpine; Piperidines; Pirenzepine; Receptors, Muscarinic; Seizures

In this study we investigated the effects of antimuscarinics with different selectivity on the intestinal migrating myoelectric complex (MMC) in five fasting, conscious dogs, chronically fitted with electrodes along the small bowel. Furthermore, we evaluated the chronotropic and mydriatic effects to assess the in vivo selectivity of the agents tested. Dose-response studies were performed with the following drugs administered i.v.: atropine, telenzepine (M1 antagonist), AF-DX 116 [11,2-(diethylamino)methyl-1-piperidinyl-acetyl-5,11-dihydro-6H-pyrido-2 ,3b- 1,4-benzodiazepine-6-one (M2 antagonist)] and 4-diphenylacetoxy-N- methylpiperidine methiodide (4-DAMP) (M3 antagonist). All the antimuscarinics tested dose-dependently increased the duration of the MMC period and inhibited spike activity, except low-dose telenzepine (3-10 nmol/kg), which shortened the MMC period and stimulated spike activity. High-dose telenzepine (> 100 nmol/kg) mimicked the inhibitory effect of atropine on the intestine. ED50 values for delay of MMC onset were 87,232, > 10,000 and 129 nmol/kg for atropine, telenzepine, AF-DX 116 and 4-DAMP, respectively. At doses lengthening the MMC period, atropine and 4-DAMP also induced tachycardia and mydriasis. At doses shortening the MMC period, telenzepine had no effect on pupil diameter or heart rate, except at the dose of 10 nmol/kg, which reduced heart rate. Finally, AF-DX 116, at doses inducing marked tachycardia, had a minor intestinal effect and no mydriatic effect. The present data are consistent with the hypothesis that both M1 and M3 receptors are involved in the regulation of the MMC: M1 receptors are probably located on an inhibitory pathway, whereas M3 receptors mediate excitatory stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Atropine; Dogs; Female; Gastrointestinal Motility; Heart Rate; Male; Parasympatholytics; Piperidines; Pirenzepine; Pupil; Receptors, Muscarinic

1. The muscarine receptor mediating electrically-stimulated acid secretion in the mouse isolated stomach was characterized using a variety of muscarine receptor antagonists confirming the M1 nature of the antagonist effect of telenzepine. 2. Field stimulation (7 V, 10 Hz, 0.5 ms) resulted in a plateau acid secretion over at least 90 min which was completely blocked by either 1 mumol/l TTX or H2 receptor antagonists (100 mumol/l cimetidine or 10 mumol/l lupitidine). Ranitidine, which is known to potently inhibit mucosal acetylcholine esterase, was ineffective. Compound 48/80 at 100 mumol/l, which depletes mucosal histamine stores, initially mimicked electrical stimulation but subsequently prevented it from inducing acid secretion. 3. 10 muscarine receptor antagonists with differing relative affinities for M1, M2 and M3 receptors were introduced at 1 mumol/l to inhibit electrically-stimulated acid secretion. The percentages inhibition were plotted against binding affinities of the antagonists at either M1, M2 or M3 binding sites. A statistically significant correlation between functional and binding data was detected only when based on M1 affinities. 4. It is concluded that field stimulation, which probably mimicks vagal drive, results in muscarinic M1 receptor activation on paracrine cells to release histamine. Histamine then stimulates parietal cells to secrete acid. Hence, according to the present and our previous data, telenzepine inhibits acid secretion under these conditions by blocking M1 receptors at least partially located on histamine-releasing paracrine cells.

Topics: Acetylcholine; Alkaloids; Animals; Anti-Ulcer Agents; Electric Stimulation; Furans; Gastric Acid; Gastric Mucosa; Histamine; Mice; Muscarinic Antagonists; Naphthalenes; p-Methoxy-N-methylphenethylamine; Parasympatholytics; Piperidines; Pirenzepine; Stomach; Thiazepines; Vagus Nerve

A method was developed to determine the affinities of antimuscarinic drugs at M1 receptors. [3H](+/-)-Telenzepine served as radioligand in crude preparations of calf superior cervical ganglia and showed high affinity for a single receptor population, consisting of M1 receptors (KD = 1.12 nM). Kinetic experiments showed monophasic association (k1 = 0.017 min-1 nM-1) and dissociation (k-1 = 0.017 min-1) kinetics, the half-life of dissociation being 41 min at 37 degrees C. The kinetic KD value amounted to 1.00 nM. M1 affinities for pirenzepine, methoctramine, hexahydro-sila-difenidol and p-fluoro-hexahydro-sila-difenidol determined in competition experiments were similar to those found in functional studies with M1 receptors in rabbit isolated vas deferens. The binding assay was used to determine the affinities of the (R) and (S) enantiomers of tertiary (trihexyphenidyl, hexahydro-difenidol, hexbutinol, p-fluoro-hexbutinol) and quaternary muscarinic antagonists (trihexyphenidyl methiodide, hexbutinol methiodide). Comparison of results obtained with the rabbit vas deferens suggested that the ionic environment may influence the affinities.

Topics: Animals; Binding, Competitive; Cattle; Ganglia; Half-Life; In Vitro Techniques; Male; Neck; Piperidines; Pirenzepine; Rabbits; Radioligand Assay; Receptors, Muscarinic; Tritium; Vas Deferens