TABLE 1.

Average phase shift in locomotor activity induced by heat pulses at different temperatures and times in a daily cycle

Heat pulse treatmenta	Peak activity (CTe ± SEM [n])	Phase shift (h)b
Control	12.7 ± 0.2 (58)
T15.0, 37°C	15.0 ± 0.2 (47)c	−2.3
T15.0, 34°C	13.5 ± 0.3 (29)c	−0.8
T15.0, 31°C	12.6 ± 0.2 (28)d	0.1
T20.5, 37°C	12.5 ± 0.3 (16)d	0.2
T21.5, 37°C	12.5 ± 0.2 (27)d	0.2
T23.0, 37°C	12.9 ± 0.3 (14)d	−0.2

^aFlies were exposed to several LD cycles at 25°C and heat pulsed for 30 min at the indicated temperatures in the dark phase of the last LD cycle. Heat-pulsed flies were then returned to 25°C, and locomotor activity was continuously recorded during the following 7 to 10 days of DD. 

^bCalculated by subtracting the time in a day when peak activity occurred in control untreated flies from the values obtained for heat-pulsed flies. A negative value indicates a phase delay. 

^cDaily peak of activity significantly different from the control (P < 0.005 by two-tailed t test). 

^dDaily peak of activity not significantly different from the control (P ≥ 0.5 by two-tailed t test). 

^eCT, circadian time, which is equivalent to zeitgeber time (ZT).