1. Agonist-antagonist interactions at acetylcholine (ACh) muscarinic receptors have been analysed by use of an improved urinary bladder assay, isolated and intact, from the mouse. With 5-methylfurmethide as agonist, validated cumulative concentration-effect curves were obtained in less than 7 min by re-dosing before the response plateaux began to fade. 2. The pKB value estimated for pirenzepine...

The present study investigated pharmacological characterizations of muscarinic acetylcholine receptor (AChR) subtypes involving ACh-induced endothelium-independent vasodilatation in rat mesenteric arteries. Changes in perfusion pressure to periarterial nerve stimulation and ACh were measured before and after the perfusion of Krebs solution containing muscarinic receptor antagonists. Distributio...

The aim of the present study was to investigate whether muscarinic M1 receptor activation induces intestinal relaxation via nerve-dependent nitric oxide formation. Mechanical activity in longitudinal segments of rat jejunum was recorded isotonically in organ baths. The muscarinic M1 receptor agonist 4-[[[(3-Chlorophenyl)amino]carbonyl]oxy]-N,N,N,-trimethyl-2-butyn- 1-ammonium chloride (McN-A-34...

Muscarinic agonists can stimulate rather than inhibit cardiac muscle in some preparations. In left atria from hatched chicks, treatment with pertussis toxin reversed the membrane action of carbachol from hyperpolarization to depolarization and reversed the inotropic effect of carbachol from negative to positive. Acetylcholine also depolarized the membrane and increased the force of contraction ...

The role of muscarinic receptors in several diseases including cancer has recently emerged. To evaluate the hypothesis that muscarinic acetylcholine receptors may play a role in bladder cancer as well as in other tumor types, we investigated their expression in bladder tumor specimens. All examined samples expressed the M1, M2 and M3 receptor subtypes. We also found that the level of M2 transcr...

NAKANE, T., FURUKAWA, Y. and CHIBA, S. Anti-Muscarinic Effect of Alinidine on Acetylcholine-Induced Vasodilation in Isolated and Perfused Dog Coronary Arteries. Tohoku J. Exp. Med., 1991, 165 (2),105-113 The effect of alinidine, a bradycardic agent, on the vasodilator responses to acetylcholine was examined in isolated and perfused dog coronary arteries. Single injections of acetylcholine (10-1...

The muscarinic receptor mediating vasodilation of resistance vessels in the rat isolated, constant-pressure perfused kidney (preconstriction by 10(-7) M cirazoline) was characterized by subtype-preferring agonists and selective antagonists. The agonists produced vasodilation with the following rank order of potency: arecaidine propargyl ester (APE) > 5-methylfurtrethonium = methacholine = oxotr...

We employed a brain microdialysis method to examine the possible regulation of spontaneous acetylcholine (ACh) release in the hypothalamic vasopressinergic supraoptic nucleus (SON) of rats. We monitored the basal ACh release in the SON-microdialysate. The addition of tetrodotoxin (10(-6) M) to the perfusate (saline containing 10(-4) M physostigmine) decreased the basal ACh release. A muscarinic...

Trace conditioning requires that a transient representation of the conditional stimulus (CS) persists during the time interval between the CS offset and the onset of the unconditional stimulus. According to one hypothesis, this transient CS representation is supported by endogenous activity in "persistent-firing" neurons of perirhinal cortex (PR). By definition, persistent-firing neurons discha...

There is consensus that muscarinic and nicotinic receptors expressed in vestibular hair cells and afferent neurons are involved in the efferent modulation of the electrical activity of the afferent neurons. However the underlying mechanisms of postsynaptic control in neurons are not well understood. In our work we show that the activation of muscarinic receptors in the vestibular neurons modula...