| Abstract: | Peták, Ferenc, Zoltán Hantos, ÁgnesAdamicza, Tibor Asztalos, and Peter D. Sly. Methacholine-inducedbronchoconstriction in rats: effects of intravenous vs. aerosoldelivery. J. Appl. Physiol. 82(5):1479-1487, 1997. To determine the predominant site of action ofmethacholine (MCh) on lung mechanics, two groups of open-chestSprague-Dawley rats were studied. Five rats were measured duringintravenous infusion of MCh (iv group), with doubling of concentrationsfrom 1 to 16 µg · kg 1 · min1.Seven rats were measured after aerosol administration of MCh with dosesdoubled from 1 to 16 mg/ml (ae group). Pulmonary input impedance(ZL) between 0.5 and 21 Hz wasdetermined by using a wave-tube technique. A model containing airwayresistance (Raw) and inertance (Iaw) and parenchymal damping (G) andelastance (H) was fitted to theZL spectra. In the iv group, MChinduced dose-dependent increases in Raw peak response 270 ± 9 (SE) % of the control level; P < 0.05] and in G (340 ± 150%;P < 0.05), with no increase inIaw (30 ± 59%) orH (111 ± 9%). In the ae group, thedose-dependent increases in Raw (191 ± 14%;P < 0.05) andG (385 ± 35%; P < 0.05) were associated with a significant increase in H (202 ± 8%; P < 0.05).Measurements with different resident gases air vs. neon-oxygenmixture, as suggested (K. R. Lutchen, Z. Hantos, F. Peták,Á. Adamicza, and B. Suki. J. Appl.Physiol. 80: 1841-1849, 1996)] in thecontrol and constricted states in another group of rats suggested thatthe entire increase seen in G during the ivchallenge was due to ventilation inhomogeneity, whereas the aechallenge might also have involved real tissue contractions viaselective stimulation of the muscarinic receptors. |
