Figure 1.

Nicotine diminishes the drive to breathe in sleeping wild-type mice. Ventilation (V_E) was measured by whole-body plethysmography (A) after a single i.p. injection of saline (○, morning studies) or nicotine (■, 0.5 mg⋅kg⁻¹, afternoon studies). The HVR (period of hypoxia = shaded panels) was then recorded at +13 min, (B, mice awake) and again 1 h after injection (asleep, C). Only HVRs elicited during sleep are shown (D and E). The downward displacement of the curve of wild-type mice signaled diminished ventilatory (breathing) drive after nicotine exposure (D; *, P = 0.015), an effect not evident in mutant mice (E; P = 0.8 nicotine vs. saline).