Effect of morphine and acetylcholine on contractile activity and cyclic AMP in guinea-pig ileum

1990 ◽  
Vol 10 (1) ◽  
pp. 113-119 ◽  
Author(s):  
L. F. Alguacil ◽  
M. P. Lopez-Ruiz ◽  
J. C. Prieto ◽  
C. Alamo ◽  
E. Cuenca
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Prolonged Exposure ◽  
Contractile Activity ◽  
Inhibitory Effect ◽  
Guinea Pig Ileum ◽  
Camp Content ◽  
Twitch Response ◽  
Spontaneous Movements ◽  
Camp Levels

Neither acute nor prolonged exposure to morphine altered cAMP content or spontaneous movements of longitudinal muscle-myenteric plexus strips of the guinea-pig ileum. By contrast, exogenous acetylcholine or electrical stimulation of the strips elicited both a decrease of cAMP concentration and a twitch response. Atropine blocked the effects of stimulation on these parameters. Addition of morphine to electrically stimulated strips inhibited the twitch response but did not affect cAMP levels. Incubation with morphine led to the development of tolerance to the inhibitory effect on twitch activity and prevented the fall in cAMP normally elicited by electrical stimulation. These results suggest that muscarinic activation is associated with a reduction of cAMP content, an effect which would be impaired in opiate-tolerant tissues.

Effects of neurotransmitter release on mucosal transport in guinea pig ileum

1983 ◽  
Vol 245 (6) ◽  
pp. G745-G750 ◽  
Author(s):  
H. J. Cooke ◽  
K. Shonnard ◽  
G. Highison ◽  
J. D. Wood
Keyword(s):  
Electrical Stimulation ◽  
Guinea Pig ◽  
Neurotransmitter Release ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Scorpion Venom ◽  
Enteric Neurons ◽  
Sodium Absorption ◽  
Guinea Pig Ileum ◽  
Ileal Mucosa

Scorpion venom (Leiurus quinquestriatus), a substance that evokes neurotransmitter release by depolarizing neurons, was used to activate enteric neurons in short-circuited guinea pig ileum. Scorpion venom increased transmural potential difference and short-circuit current, and this response was similar to the increase that occurred after electrical stimulation of enteric neurons. The stimulus- or venom-evoked response in short-circuit current was abolished by tetrodotoxin. Atropine reduced by 47% the increments in short-circuit current produced by either electrical stimulation or venom. Scorpion venom increased active chloride secretion in short-circuited guinea pig ileal mucosa but had no significant effect on active sodium absorption, residual flux, or total tissue conductance. No morphological changes in transmission electron micrographs of ileal mucosa treated with scorpion venom were evident compared with controls. Alanine caused an increase in short-circuit current in venom-treated tissue that was similar to control values. These results show that scorpion venom mimics the mucosal effects of electrical activation of enteric neurons. These results suggest that a significant component of both scorpion venom action and the response to electrical field stimulation is mediated by neural release of acetylcholine, which activates epithelial muscarinic receptors.

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