Fig. 8.

Airway contraction in response to an elevation of [Ca²⁺]_i, with and without agonist, in rat and mouse airways. MCh (200 nM) induced contractile responses (∼40%) in rat (top, left) and mouse (bottom, left). After Ca²⁺ permeabilization by caffeine/ryanodine treatment and exposure to 0 [Ca²⁺]_o, the [Ca²⁺]_i was low. Exposure to 1.3 mM Ca²⁺ induced ∼40% contraction in rat airways but only a transient contraction in mouse airways. Exposure to MCh induced an additional contraction in rat airway but a full contraction in the mouse airway. Compared with normal airways, 1 μM MCh induced ∼5% more contraction in the Ca²⁺-permeabilized rat airway but similar contraction in the Ca²⁺-permeabilized mouse airway.