Gq-linked NK2 receptors mediate neurally induced contraction of human sigmoid circular smooth muscle

Interleukin 1β-Induced Production of H2O2Contributes to Reduced Sigmoid Colonic Circular Smooth Muscle Contractility in Ulcerative Colitis

“…Consistent with previously reported data (Cao et al, 2000), the endogenous neurotransmitter neurokinin A caused dose-dependent contraction of normal human sigmoid circular muscle strips. In strips from patients with ulcerative colitis neurokinin A-induced contraction was significantly reduced compared with normal muscle strips ( Fig.…”

“…After the mucosa was removed by sharp dissection under a microscope, consecutive circular muscle strips (10 mm in length, 2 mm in width) of normal and ulcerative colitis sigmoid colon were cut with razor blades held in a metal block 2 mm apart. The strips were mounted in separate 1-ml muscle chambers as described in detail previously (Cao et al, 2000). All muscle strips were initially stretched to 2.5 g of passive force.…”

“…Sigmoid circular muscle was cut into thin muscle strips (approximately 1 mm in width) and digested in HEPES-buffered solution to obtain isolated smooth muscle cells, as described previously (Cao et al, 2000). The collagenase solution contained 0.5 mg/ml collagenase Sigma type F, 1 mg/ml papain, 1 mg/ml bovine serum albumin, 1 mM CaCl 2 , 0.25 mM EDTA, 10 mM glucose, 10 mM HEPES (sodium salt), 4 mM KCl, 125 mM NaCl, 1 mM MgCl 2 , and 10 mM taurine.…”

“…Solutions in the pressure ejection micropipettes were identical to the bathing solutions except the agonists. Ca 2ϩ measurements were obtained using a modified dual excitation wavelength imaging system (IonOptix Corp., Milton, MA) as described previously (Cao et al, 2000). Ratiometric images were masked in the region outside the borders of the cell because low photon counts give unreliable ratios near the edges.…”

“…We have previously examined normal motor function of human sigmoid circular muscle and have shown that neurokinin A may be an important excitatory neurotransmitter because contraction induced by electrical field (i.e., neural) stimulation is abolished by an NK-2 receptor antagonist, and not affected by NK-1 receptor antagonist or by atropine (Cao et al, 2000), but the mechanism of motor dysfunction in ulcerative colitis is not fully understood.…”