Figure 6.
Circadian variations of the rod receptive field size and input resistance (Ri)
A, circadian variations in the size of the receptive field. Representative examples of receptive field size measurements of single rods obtained during the subjective day-1 (SD1) and subjective night (SN). Cell RMP was –38.0 mV (SD1) and –43.0 mV (SN). B, average values of the space constant (λ) measured during the day (D), night (N), subjective day-1 (SD1), subjective day-2 (SD2), or subjective night (SN). A two-way ANOVA of the data was performed. The between-group factor was the type of lighting cycle (i.e. 12 h light–12 h dark cycle or circadian cycle) and the intra-group was time of D (D or N). ANOVA of the data revealed significant time of D effect (F(1,33) = 110.90, P < 0.001) but no type of lighting cycle effect (F(1,33) = 2.88, P = 0.10) or time of D × type of lighting cycle effect (F(1,33) = 1.29, P = 0.26). n is shown for each condition on the figure (1 cell retina). Error bars, SEM. C, comparison of Ri measurements obtained during the day (D), night (N), subjective day-1 (SD1), subjective day-2 (SD2), or subjective night (SN). Ri of the recorded rods was measured using a 5 mV voltage step (see Methods for details). A two-way ANOVA of the data was performed. The between-group factor was the type of lighting cycle (i.e. 12 h light–12 h dark cycle or circadian cycle) and the intra-group was time of D (D or N). ANOVA of the data revealed significant time of D effect (F(1,58) = 12.51, P < 0.001) but no type of lighting cycle effect (F(1,58) = 1.67, P = 0.20) or time of D × type of lighting cycle effect (F(1,58) = 0.35, P = 0.56). n is shown for each condition on the figure (1 cell retina–1). Error bars, SEM.