Fig 2: PDE9A is localized in the inner retina. (A) Low magnification (4×) image of a whole mount PDE9A KO retina stained for X-gal (blue); on, optic nerve head. (B) Higher magnification (40×) image of the ganglion cell layer (GCL) in the same retina as in (A): the stained cells occupy less than 50% of the area. (C) A cryosection of a KO retina stained for X-gal. X-gal staining is present in both the inner nuclear layer (INL) and GCL. IPL: inner plexiform layer. (D) Cryosection of KO retina showing X-gal staining in the ciliary body.

Fig 3: Absence of PDE9A slows the falling phase of the b-wave of a saturating flash under photopic conditions. (A) Average responses of WT and KO retinas to a saturating flash (1000 scot cd s m−2) after 2 s light adaptation. The responses to both the first and second saturating flashes (presented before and after stimulation with UV and green light, respectively) in each retina were averaged. (B) Response amplitudes of the a- and b-waves at the saturating flash are reduced in KO (13 WT and 14 KO mice). (C) The times taken by the b-wave to rise and fall to 66% of its amplitude and the duration between them. (D,E) Average response of WT and KO retinas to the first (1) and second (2) saturating flash. (F) The width of the b-wave at 50% of its amplitude for the first (1) and second (2) saturating flashes increased in KO.

Fig 4: PDE9A does not contribute to the ERG under scotopic conditions. For all figures, WT is drawn in black and KO in red. Also for all figures, data are plotted as average ±s.e.m. When the s.e.m. cannot be seen, it is smaller than the symbol. (A,B) Representative responses to increasing light intensities (0.2– 600 R*/rod) from age matched WT (A) and PDE9A KO (B) retinas. (C) Average b-wave amplitudes vs. flash intensity for WT (black squares; 16–22 records) and KO (red diamonds; 18–28 records) mice. (D) Illustration of the parameters used to characterize the kinetics of the b-wave. Stimulus onset is designated by an upward black arrow, 66% of the peak amplitude is indicated by the blue line and 50% by the green line. Time taken by the b-wave to rise from the stimulus onset to 66% of its peak amplitude (left dashed blue arrow) or to 50% of its amplitude (left dashed green arrow) were used for comparison of its kinetics. Time taken by the b-wave to fall to 66 or 50% of its peak amplitude is indicated by the right blue and green arrows. (E) Times taken by the b-wave to rise (triangles) and fall (squares) to 66% of its amplitude, and the duration between them (width, circles) at the measured intensities.

Fig 5: PDE9A accelerates the kinetics of the photopic b-wave. (A) Average responses from WT and KO retinas to ultra-violet (UV) light of intensity 1.65 × 104 photons μm−2 (17 records were averaged for WT and 24 for KO). (B) Amplitudes of the a- and b-waves from WT (n = 9–12 mice) and KO (n = 12–13) retinas at increasing intensities of UV light. (C) The time taken by the b-wave to rise and fall to 66% of its amplitude at different intensities of stimulation. The time taken by the b-wave to rise and decay to 66% of its amplitude was significantly longer in KO at all intensities. (D) Average response of WT and KO retinas to green light of intensity 3.2 × 104 photons μm−2 (n = 16 for WT and 19 for KO). (E) Amplitudes of the a- and b-waves from WT (n = 7–11) and KO (n = 2–11). Mice at increasing intensities of green light. (F) The times taken by the b-wave to rise and fall to 66% of its amplitude: both parameters are significantly longer in KO.