Sd. Smid et al., Oesophagitis-induced changes in capsaicin-sensitive tachykininergic pathways in the ferret lower oesophageal sphincter, NEUROG MOT, 10(5), 1998, pp. 403-411
Prolonged oesophageal acidification may impair lower oesophageal sphincter
(LOS) function in reflux disease. The aim of this study was to investigate
aspects of altered LOS innervation in a model of oesophagitis. Oesophagitis
was induced by acid (HCl, 0.15 M) and pepsin (0.1% w/v) infusions in anaes
thetized ferrets. LOS muscle strip responses to the following stimuli were
measured in vitro from control and acid/pepsin-treated ferrets: electrical
field stimulation (EFS; 1-50 Hz), potassium chloride KCl; 20 mM), substance
P, [beta-Ala(8)]-neurokinin A 4-10, [Sa(r)9, Met (O-2)(11)]-substance P (a
ll 10(-10) to 10(-6) M) and capsaicin (10(-8) to 10(-6) M). LOS relaxation
occurred in response to all stimuli except [beta-Ala(8)]-neurokinin A 4-10,
which evoked contraction. In muscle strips from acid/pepsin-treated animal
s there were no differences in amplitude or sensitivity of relaxation follo
wing EFS, KCI or substance P vs controls. However, the inhibitory response
to capsaicin was increased four-fold (10(-8) M; P < 0.05) and an increased
sensitivity of the inhibitory response to [Sar(9), Met (O-2)(11)]-substance
P occurred (pD(2) = 8.64 +/- 0.12 acid/pepsin-treated vs 7.94 +/- 0.24 con
trol, P < 0.05). We conclude that in acute oesophagitis, increased sensitiv
ity of capsaicin-activated inhibitory pathways occurs in which activation o
f NK-1 receptors plays an integral role in the ferret LOS.