Trigeminal nerve activity and buccal pressure as an index of total inspiratory activity in the bullfrog.

In bullfrogs with glottis occluded and lungs artificially ventilated, the buccal cavity contractors (BCconts) were found to contract isometrically, meaning that peak buccal pressure (OBP) well represents the total inspiratory nerve activities (TIAs) of BCconts. Unilateral sectioning of the trigeminal (V), hypoglossal, facial, or vagal nerve reduced the magnitude of OBP by 43.3, 28.8, 10.9, or 4.3%, respectively. The integrated peak V activity (I-ENGv) showed a linear relationship to OBP (r = 0.944) in the glottis occluded frog, but a curvilinear relationship to peak buccal pressure (peak BP) in the spontaneously breathing frog during inflation period. The latter relationship was better fitted by a hyperbolic equation (r = 0.943) than by a linear equation (r = 0.927) (p less than 0.001). The relationship between I-ENGv and peak BP showed a hysteresis during deflation period. It was suggested that both I-ENGv and peak BP can be used as a measure of TIAs, but use of the latter requires some reservations.