Central nicotinic receptor blockade inhibits emotionally conditioned pressor responses in rats

A conditioned stimulus previously paired with electric footshock produced an increase in blood pressure in conscious, freely moving rats. The conditioned pressor response was reproducible. Intracerebroventricular injection of the nicotinic receptor antagonists hexamethonium (1–10 g) or pentolinium (10 g) but not the muscarinic receptor antagonist methylatropine (3 g) produced an inhibition of the conditioned pressor response, whereas intraarterial injection of hexamethonium (10 g) did not affect the response. Intraventricular injection of the cholinesterase inhibitor physostigmine (3–10 g) produced an enhancement of the conditioned pressor response. These results are consistent with the possibility that central nicotinic receptors play a role in the expression of the emotionally conditioned pressor response in rats.     

Muscarinic acetylcholine receptor is involved in acetylcholine regulating stomatal movement

In animal cells, action of acetylcholine depends on its binding with its two specific receptors on the plasma membrane: the nicotinic and muscarinic respectively. The present investigation has shown that agonists of muscarinic receptor (muscarine) could induce stomatal opening, while the antagonists (atropine) could block stomatal opening induced by acetylcholine. Their effects can only be realized in medium containing Ca²⁺, but not in medium containing K⁺. The results tend to reveal that the muscarinic receptor is involved in acetylcholine-induced stomatal movement.     

Muscarinic involvement in vascular and adrenal medullary responses to splanchnic nerve stimulation in conscious calves

Stimulation of the peripheral end of the right splanchnic nerve (4 Hz for 10 min) in the presence of hexamethonium caused a small but significant rise in mean aortic blood pressure which was subsequently abolished by atropine. There were also small but significant increases in the outputs of catecholamines, [Met⁵]-enkephalins and corticotrophin releasing factor (CRF) from the right adrenal gland. The catecholamine response was roughly halved after atropine while the outputs of enkephalins and CRF were unaffected. It is concluded that splanchnic sympathetic postganglionic neurones supplying the vasculature are completely blocked by cholinergic blockade whereas adrenal medullary responses persist in an attenuated form.     

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Summary Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.     

Acetylcholine receptors in the gastrulating chick embryo

Summary Muscarinic acetylcholine receptors are present in the gastrulating chick embryo.     

Anti-muscarinic activity of a family of C11N5 compounds isolated fromAgelas sponges

In a search for potential target sites for C₁₁N₅ compounds obtained from marine sponges of the genusAgelas we evaluated their interaction with muscarinic acetylcholine receptors from rat brain membranes. In competition experiments with³H-QNB these compounds displayed the following rank order of potency: sceptrin>oroidindibromosceptrinclathrodin. Sceptrin (50 M) was shown to be a competitive inhibitor of³H-QNB binding as revealed by Scatchard analysis. The results demonstrate the ability of these compounds to interact with multiple target molecules in the micromolar range.     

大鼠耳蜗血管纹胆碱能M受体的表达及意义

目的:研究胆碱能M受体在耳蜗血管纹的表达.方法:采用RT-PCR技术检测大鼠耳蜗血管纹上胆碱能M受体的基因表达.结果:扩增出标志M2、M3、M4和M5受体亚型基因表达的PCR产物,未扩增出标志M1受体亚型的产物.结论:胆碱能M2、M3、M4和M5受体亚型在耳蜗血管纹有表达,提示胆碱能M受体可能参与了血管纹功能的调节,为研究胆碱能M受体在血管纹上的功能提供分子生物学基础.     

Antiarrhythmic peptide has no direct cardiac actions

Summary The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic, peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force, in papillary muscle, no biologically significant effects of AAP could be determined in any, preparation, suggesting that its antiarrhythmic, effects are not mediated by direct membrane actions.     

Sympathetic,muscarinic vasodilation in cranial vessels of the cat

Summary Pressor responses evoked by stimulation of the preganglionic sympathetic trunk of the feline superior cervical ganglion have been recorded in vivo from the vascular bed perfused by one external carotid and the vertebral artery. When vasoconstrictor activity is blocked and potential vasodilator activity enhanced by close, intracarotid injection of guanethidine and prostaglandin F₂ respectively, stimulation evokes a weak pressor response followed, on cessation of stimulation, by a prolonged vasodilation lasting for 6–8 min. The magnitude and duration of the poststimulation vasodilation was reduced significantly by atropine. Due to the prolonged nature of the vasodilation, it is unlikely that a sympathetic cholinergic vasodilation in the classical sense is involved.     

Positive and negative inotropic effects of carbachol on the embryonic chick atrium

The effect of carbachol on twitch tension of atrial preparations from chick embryos of different incubation ages (3–14 days) was studied. At every age carbachol evoked negative (at low concentrations) and positive (at higher concentrations) inotropic responses. Maximal response values for both effects increased with age; in 3- and 5-day atria the positive inotropic response prevailed. The muscarinic antagonist pirenzepine inhibited the positive (on 5-day atria) and negative (on strips of 14-day atria) inotropic effects of carbachol with pA₂ values of 6.8 and 8.0, respectively, suggesting that muscarinic receptors mediating these effects belong to different receptor subtypes.