Muscarinic response

Kenakin, T. P., and Boselli, C. (1989). Pharmacologic discrimination between receptor heterogeneity and allosteric interaction Resultant analysis of gallamine and pirenzeipine antagonism of muscarinic responses in rat trachea. J. Pharmacol. Exp. Ther. 250 944—952. 

Dascal N, Landau EM, Lass Y. 1984. Xenopus oocyte resting potential, muscarinic responses and the role of calcium and cyclic GMP. J Physiol 352 551. 

Acetylcholine (9.12) binds both types of cholinergic receptors muscarinic and nicotinic (Figure 9.9). The names of these receptor types were based on muscarine (9.13) and nicotine (9.14), selective agonists for each receptor. A muscarinic response is characterized by nausea, salivation, and tearing. Nicotinic responses are noted by an acceleration of the heart rate. Acetylcholine s ability to elicit a response from both subtypes of receptors may imply that different conformations of acetylcholine may be responsible for binding to each receptor. 

McCormick DA, Prince DA. 1985. Two types of muscarinic response to acetylcholine in mammalian cortical neurons. Proc Natl Acad Sci USA 82 6344-6348. 

Libri V, Constant A, Calaminci, M. Nistico G. 1994. A comparison of the muscarinic response and morphological properties of identified cells in the guinea-pig olfactory cortex in vitro. Neuroscience 59 331-347. 

One major question relates to whether the nonselective cation channels activated by norepinephrine and acetylcholine are the same protein. Inoue and Kuriyama (Inoue and Kuriyama 1993) studied the activation of both currents in the rabbit portal vein, one of the few vascular preparations in which excitatory muscarinic responses are observed. Based on lack of an additional current response once Icat was fully activated by one agonist, and similar current I-V relationships, current activation and deactivation kinetics, single channel conductance, and block by Cd they concluded that adrenergic and muscarinic stimulation activates a common nonselective cation channel. On the other hand, substantial differ-... 

Uceda G, Artalejo AR, de la Puente MT, Lopez MG, Albillos A, Michelena R Garcia AG, Montiel C. Modulation by L-type Ca channels and apamin-sensitive K-t channels of muscarinic responses in cat chromaffin cells. Am J Physiol 1994 266(5 Rt l) C1432-9. 

In Nature, no less than two molecules of ACh must combine with the a-protein to evoke a response. One microsecond pulse of ACh produces, in skeletal muscle, an apparently instant response that lasts for 10 fJLS. These figures suggest that the receptor directly controls the micropore, and that no phosphorylation step is required. Thus the nicotinic response is much simpler and more direct than that postulated by Greengard for the muscarinic response (P-522). 

Wilkes JM, Kajimura M, Scott DR, et al. Muscarinic responses of gastric parietal cells. J Membr Biol 1991 122 97. 

Isodihydrohistrionicotoxin at 4 pM has little or no effect on muscarinic responses in ileum or atrium 183). Histrionicotoxins are, however, noncompetitive muscarinic antagonists in neural cell lines 49), suggestive of interaction at a nonreceptor site, perhaps at a channel component. 

Cardiac preparation Guinea pig atrium Blockade muscarinic responses (183)... 

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