Mechanisms controlling function in the clasp and sling regions of porcine lower oesophageal sphincter.
BACKGROUND
Characterization of functional differences between lower oesophageal sphincter (LOS) clasp and sling muscles might aid the development of more specific pharmacological and surgical approaches for the treatment of motility disorders.


METHODS
Circular LOS strips from 25 adult pigs were studied in organ baths to compare the physiology of clasp and sling fibres.


RESULTS
Sling strips developed greater tone than clasp fibres (mean(s.e.m.) 7.59(0.89) versus 4.72(0.67) g; P = 0.017). LOS tone was more dependent on extracellular calcium in clasp strips and on the activity of cholinergic enteric motor neurones (EMNs) in sling strips. The amplitude of maximal relaxation caused by electrical field stimulation (EFS, 3Hz) of EMNs was greater in clasp strips (mean(s.e.m.) 74.5(2.3) versus 58.1(2.2) per cent of tone; P < 0.001). EFS-induced relaxation was reduced in clasp fibres and fully blocked in sling fibres by nitrergic blockade with 10 micromol/l 1H-[1,2,4]oxadiazole-[4,3-alpha]quinoxalin-1-one (ODQ). The amplitude of EFS cholinergic responses was significantly greater in sling fibres. In the clasp region, relaxation caused by stimulation of EMNs with 100 micromol/l nicotine was reduced by ODQ. In sling fibres, nicotine induced relaxation at rest and cholinergic contraction following ODQ.


CONCLUSIONS
Clasp and sling fibres of the porcine LOS show marked intrinsic functional differences. This should be considered when developing more specific approaches to human LOS motility disorders.
Farré
R
R
Dr Francisco Vilardell Foundation of Gastroenterology and Research Group for the Study of Gastrointestinal Motility, Autonomous University of Barcelona, Bellaterra, Spain.
Aulí
M
M
Lecea
B
B
Estrada
O
O
Suñol
X
X
Clavé
P
P
D000818:Animals; D004558:Electric Stimulation; D049630:Esophageal Sphincter, Lower / Q000502:physiology* / Q000601:surgery; D009046:Motor Neurons / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D013552:Swine
D018377:Neurotransmitter Agents; D011978:Receptors, Nicotinic