Dim scotopic illumination accelerates the reentrainment following simulated jetlags in a diurnal experimental model, Drosophila

Abstract

Jetlag results from the misalignment between the endogenous circadian timing and the civil timing after a transmeridian flight. Efficacy of the dim nocturnal illumination (0.03 lx) in accelerating the reentrainment following simulated jetlags in Drosophila biarmipes was examined by subjecting the flies to 24 h light-dark cycles in which the 12 h photophase was at 300 lx for all flies but the scotophase was at 0 and 0.03 lx for the control and experimental flies, respectively. Reentrainment was always faster in the experimental flies than the control ones. Moreover, unlike melatonin, the dimly lit nights accelerated the reentrainment following both, the phase advance and delay of the light-dark cycles. This study might have potential application as a non-drug jetlag treatment.

Keywords: Drosophila biarmipes; circadian; dim nocturnal illumination; jetlag; reentrainment.

Figure 1. Entrainment and free-run in D. biarmipes. The actograms of the representative control and experimental males of D. biarmipes which were entrained by LD 12:12 (A) and LS 12:12 (C) cycles, respectively, and then transferred to DD on the day 11 (oblique arrow). The mean activity profiles of 49 control (B) and experimental (D) males during the entrainment are showing the circadian peaks (dark arrows), the masking peaks (open arrows) and the phase relationship between the Aoff of the M peak and Aon of the E peak (Ψ_M-E). The dark and open time bars denote the photophase (300 lx) and scotophase (0 lx), respectively, the long dark time bars denote DD and the hatched portion of the time-bars denotes the dim nocturnal irradiance at 0.03 lx.

Figure 2. Simulated advance and delay jetlags in D. biarmipes. The actograms of the four representative males of D. biarmipes which were subjected to 8 h phase advance and delay of LD 12:12 cycles (A and C, respectively) and LS 12:12 cycles (B and D, respectively).

Figure 3. Transients after advance and delay jetlags. Advancing and delaying transients (mean ± S.D., n = 49 flies) endured by the activity onsets (Aon-LD) and offsets (Aoff-LD) of the control males and that of the experimental males (Aon-LS and Aoff-LS) of D. biarmipes following the advance (A) and delay shift (B) in the lighting schedules. The asterisks denote the statistically significant effects of the dim nocturnal illumination (p < 0.001).