Expression of <i>c-fos</i> in the adult zebrafish brain.

<p>A) Zebrafish were kept on 2 days of 14:10 LD followed by 2 days of DD, and brains dissected at the times indicated. RNA was extracted and qPCR was performed to evaluate the relative expression of <i>c-fos</i> mRNA. In LD there was a peak at ZT1 and ZT15 on day 1 and 2, (p<0.0001, One way ANOVA, n = 4–9). The statistical significance is shown from the post-hoc Dunnett's multiple comparison test, which used the calibrator Day 1 ZT9. In DD there was a peak at CT21 on day 3 and trough at CT9 on day 3 and day 4 (p<0.001, One way ANOVA, n = 4–9). The statistical significance is shown from the post-hoc Dunnett's multiple comparison test, which used the calibrator CT9 on day 4. The above white and black bars indicate the lighting schedule, and the shades of green reflect the light, dark and subjective dark phases. B) Adult zebrafish on a 14:10LD were given a 30 minute light pulse or kept in the dark at ZT21. Brains were dissected, RNA extracted, and qPCR performed to determine levels of <i>c-fos</i> mRNA as an indicator of neuronal activity. <i>C-fos</i> expression was five-fold higher in the brains of the light pulsed zebrafish (p<0.0001, unpaired two-tailed t-test, n = 7–8). C) <i>c-fos</i> is induced in specific brain regions in response to a light pulse in the night. Adult zebrafish maintained on a 14L:10D LD cycle were exposed to a 30-min light pulse at ZT21 or kept in the dark. <i>In situ</i> hybridisation was performed on brain sections to determine the levels of <i>c-fos</i> mRNA. Regions that show increased <i>c-fos</i> expression in response to light include i) PPp and SCN, ii) TeO, TL, Val_gra and Vam_gra and iii) Hc and Hd. iv) There is no change in expression in the rhombencephalon. Abbreviations: PPp (dorsal pretectum), SCN (suprachiasmatic nuclei), TeO (optic tectum), TL (torus longitudinalis), Val_gra (lateral valvula cerebelli), Vam_gra (medial valvula cerebelli), Hc (caudal hypothalamus) and Hd (dorsal hypothalamus).