piperidines and secoverine

1. Muscarinic cholinoceptors (MChR) in freshly dispersed rat salivary gland (RSG) cells were characterized using microphysiometry to measure changes in acidification rates. Several non-selective and selective muscarinic antagonists were used to elucidate the nature of the subtypes mediating the response to carbachol. 2. The effects of carbachol (pEC(50) = 5.74 +/- 0.02 s.e.mean; n = 53) were highly reproducible and most antagonists acted in a surmountable, reversible fashion. The following antagonist rank order, with apparent affinity constants in parentheses, was noted: 4-DAMP (8.9)= atropine (8.9) > tolterodine (8.5) > oxybutynin (7.9) > S-secoverine (7.2) > pirenzepine (6.9) > himbacine (6.8) > AQ-RA 741 (6.6) > methoctramine (5.9). 3. These studies validate the use of primary isolated RSG cells in microphysiometry for pharmacological analysis. These data are consistent with, and extend, previous studies using alternative functional methods, which reported a lack of differential receptor pharmacology between bladder and salivary gland tissue. 4. The antagonist affinity profile significantly correlated with the profile at human recombinant muscarinic M(3) and M(5) receptors. Given a lack of antagonists that discriminate between M(3) and M(5), definitive conclusion of which subtype(s) is present within RSG cells cannot be determined.

Topics: Alkaloids; Animals; Atropine; Benzhydryl Compounds; Benzodiazepinones; Binding, Competitive; Biosensing Techniques; Carbachol; Cholinergic Agonists; Cresols; Diamines; Dose-Response Relationship, Drug; Furans; Male; Mandelic Acids; Muscarinic Antagonists; Naphthalenes; Phenethylamines; Phenylpropanolamine; Piperidines; Pirenzepine; Rats; Rats, Sprague-Dawley; Receptors, Muscarinic; Submandibular Gland; Tolterodine Tartrate

We previously showed that M1 and M2 muscarinic receptors in dissociated cells of the adult rat cortex couple to phosphoinositide (Pl) and cyclic AMP (cAMP) metabolism, respectively. To further classify these receptors according to probable subtype, we have employed a group of selective muscarinic antagonists to obtain pharmacological profiles of the cortical M1 and M2 receptors, and to compare them with the muscarinic receptors in N1E-115 cells, which contain M1 receptors mediating cyclic GMP elevation and M4 receptors inhibiting cAMP levels. The M2-mediated inhibition of cAMP levels in cortex was blocked by 4-diphenylacetoxy-N-methyl piperidine methiodide (4-DAMP) with higher potency (0.29 nM) than for reported potency in cardiac tissue (approximately 10 nM), indicating that this cortical response is probably not mediated by the m2 gene product. Similarly, the potency of hexahydrosiladiphenidol (HSD) at the cortical M2 receptor (159 nM) was somewhat greater than the reported potency in cardiac tissue (295 nM). The cardioselective drugs AF-DX 116 and methoctramine blocked the cortical M2 response less potently (135 nM and 229 nM, respectively) than would be expected for involvement of the m2 gene product. Thus, the potencies of AF-DX 116, methoctramine, 4-DAMP and HSD suggest that the cortical M2 response, like the striatal M2 receptor, is mediated by a noncardiac M2 receptor, perhaps by the m4 gene product. This postulate was supported by the significant correlations between cortical and striatal M2 receptors as compared to the M4 receptor in N1E-115 cells (r = 0.92 and 0.99, respectively, P less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cerebral Cortex; Cyclic AMP; Diamines; In Vitro Techniques; Muscarinic Antagonists; Parasympatholytics; Phenethylamines; Phosphatidylinositols; Piperidines; Pirenzepine; Rats; Receptors, Muscarinic; Tumor Cells, Cultured

We used binding of [N-methyl-3H]scopolamine ( [3H]-NMS) to tissue homogenates and isometric contraction of muscle strips to characterize perinatal changes in the muscarinic receptor on rabbit gastric smooth muscle. In homogenates from fetal (28 days of gestation), 1-, 3-, and 7-day, 4- and 11-wk-old rabbits, specific binding was saturable and temperature dependent, achieved equilibrium by 10 min at 30 degrees C, and was linearly related to tissue concentration. Specific binding was 80 +/- 2% of total binding at 0.2 nM [3H]NMS. The number of binding sites was 120,000 receptors/cell, maximal during the first week of life compared with the fetus or older animals. Affinity of [3H]NMS was highest in the first week of life (Kd = 345 +/- 24 pM, 1 day old). Age did not affect Hill coefficients or Ki values; secoverine and 4-diphenylacetoxy-N-methylpiperidine methiodide were 50-fold more potent than pirenzepine. In muscle strips, bethanechol stimulated dose-dependent atropine-inhibitable isometric contraction. The doses required for half-maximal contraction were similar in both age groups (5-6 microM), but maximal contraction was fivefold greater in weanlings compared with neonates. Increasing extracellular potassium concentration resulted in similar differences, suggesting that the differences were not receptor related. These results suggest that well-differentiated M2-muscarinic receptors are functional on rabbit gastric smooth muscle during the perinatal period.

Topics: Animals; Animals, Newborn; Atropine; Bethanechol; Bethanechol Compounds; Dose-Response Relationship, Drug; Kinetics; Muscle Contraction; Muscle Development; Muscle, Smooth; N-Methylscopolamine; Phenethylamines; Piperidines; Rabbits; Receptors, Muscarinic; Scopolamine Derivatives; Stomach

The muscarinic receptor mediating vasodilatation of the rabbit aorta and dog femoral artery has been assessed using muscarinic antagonists. With the exception of pirenzepine, the antagonist affinities were similar to those reported for the ileal receptors and dissimilar to those reported for the atrial receptors. Pirenzepine exhibited an affinity (7.54) intermediate between that reported for the CNS receptors (8.4) and that reported for the ileal receptors (6.77). This value for pirenzepine was confirmed using acetylcholine as the agonist and using the dog femoral artery as the vascular tissue. It is concluded that the muscarinic receptor profile mediating vasodilatation is not easily accommodated into the current receptor classification.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Atropine; Benzodiazepinones; Carbachol; Dogs; Female; Femoral Artery; Gallamine Triethiodide; In Vitro Techniques; Male; Pancuronium; Parasympatholytics; Phenethylamines; Piperidines; Pirenzepine; Rabbits; Receptors, Muscarinic; Vasodilation