Figure 10.
The effects of spiperone and quinpirole on the rod light response kinetics and receptor field size depend on time of day
A, blocking dopamine D2-like receptors during the subjective night (SN) does not affect the nighttime state. Examples of rod responses to a series of 20 ms full-field 500 nm light flashes of increasing intensity recorded under dark-adapted conditions during the SN under control conditions (no drug, dark trace) and following the application of the D2-like receptor antagonist spiperone (10 μm, > 10 min, red trace; Aa). Averaged (Ab) and normalized (Ac) intensity–response curves and receptive field size (Ad) of rods recorded during the SN under control conditions (black points and curves) and after ∼15 min application of spiperone (red points and curves). B, application of quinpirole during the subjective day (SD) had no effect on the rod light responses kinetics or receptive field size. Examples of rod responses to a series of 20 ms full-field 500 nm light flashes of increasing intensity recorded under dark-adapted conditions during the SD under control conditions (no drug, dark trace) and following the application of the D2-like receptor agonist quinpirole (1 μm, > 10 min, green trace; Ba). Averaged (Bb) and normalized (Bc) intensity–response curves and receptive field size (Bd) of rods recorded during the SD between CT06 and CT09, under control conditions (black points and curves) and after ∼15 min application of the D2-like receptor agonist quinpirole (green points and curves). The P values in Ab, Ac, Bb, and Bc were calculated for interactions between light density and treatment (control or drug; two-way ANOVA). ns, non-significant; P > 0.05; Student's paired t test). Arrowheads in Aa and Ba indicate the peak of the response under control conditions. Error bars, SEM (1 cell retina–1). Resting membrane potential was –43.5 mV (control) and –41.5 mV (spiperone) for cell in Aa, and –42.4 mV (control) and –41.6 mV (quinpirole) for cell in Ba.