Figure 1.

Effects of N₂O inhalation on temperature and activity outcomes in Long-Evans rats (n = 12) housed in a gas-tight, thermally-graded alleyway. Black bar indicates 5-h period of steady-state 60% N₂O or paired control gas exposures. Day and night cycles correspond to white and gray bars, respectively. Temperature data are means (± SEM) of averaged individual data recorded in successive 12-min bins; distance data are means (± SEM) of binned individual sums. GEE analysis revealed highly significant main effects for condition (control vs. N₂O) (p < 0.0001) and highly significant condition by time interactions (p < 0.0001) during the period of N₂O administration. Baseline Tc was 37.12 ± 0.06°C, baseline Tsel was 25.16 ± 0.62°C, baseline Tc minus Tsel was 11.96 ± 0.60°C, and baseline distance was 41.53 ± 14.00 cm. Baseline values of these dependent variables did not differ between conditions (p > 0.05). Note that the steep recovery of Tc (A) occurs despite the persistence of conditions that favor increased heat loss [decreased Tsel (B) and increased Tc – Tsel temperature difference (C)] which suggests compensation by increased heat production.