Effects of leu-enkephalin on the mechanical activity of longitudinal and circular muscles of the small intestine of the cat.
The effects of leu-enkephalin on the spontaneous and electrically-evoked activity were studied in the longitudinal and circular strips isolated from the duodenum, jejunum and ileum of the cat. Leu-enkephalin affected the spontaneous activity of both longitudinal and circular strips, with the exception of the circular strips from the ileum, in a naloxone-dependent manner. Elimination of the neural input to the smooth muscle cells with tetrodotoxin blocked the effects of leu-enkephalin in the longitudinal and circular strips from the jejunum and in the longitudinal strips from the ileum. In the longitudinal strips from the duodenum the effect was resistant to tetrodotoxin, while in the circular strips a tetrodotoxin-sensitive component of the effect of leu-enkephalin was observed. Since leu-enkephalin evoked opposite effects in the longitudinal and circular layers of one and the same region, it is concluded that leu-enkephalin-induced modulation of the motility of the small intestine in the cat is a physiological phenomenon. Electrical stimulation, at a frequency of 5 Hz, evoked contractile responses in the longitudinal strips and relaxant, as well as low-amplitude, contractile responses in the circular strips. Rebound contractions developed after the end of stimulation in all preparations tested, with the exception of the longitudinal strips from the duodenum. Leu-enkephalin decreased the contractile components and tended to potentiate the relaxant components of the responses in a naloxone-dependent manner. Atropine inhibited the contractile components of the responses and significantly depressed the rebound contractions. Leu-enkephalin, applied after atropine, was ineffective suggesting that leu-enkephalin-induced modulation was mediated mainly through interaction with cholinergic transmission.
Venkova
K
K
Department of Experimental Pharmacology, Bulgarian Academy of Sciences, Sofia.
Radomirov
R
R
Pencheva
N
N
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D004386:Duodenum / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007583:Jejunum / Q000187:drug effects / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology
D009270:Naloxone; D004743:Enkephalin, Leucine; D001285:Atropine