Phosphodiesterase 1b (PDE1B) Regulates Spatial and Contextual Memory in Hippocampus

Figures

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  FIGURE 1. Effects of intra-hippocampal RNAi knock-down of PDE1B on open field exploration and contextual fear memory. (A) Pde1b mRNA levels measured in hippocampal cultures treated with shGFP control or shPde1b expressing AAV5 (n = 4 per treatment). PDE1B was efficiently targeted by the shRNA. (B) PDE1b protein expression 3 weeks after transfection with shPde1b or control AAV. Left: Box and whisker plots showing the expression of PDE1B in DG normalized to staining intensity in STR of the same animals (shGFP: n = 12; shPde1b: n = 15). A significant reduction in the relative expression of PDE1B protein between DG and STR was observed after shPde1b treatment. Right: Example image showing green fluorescence derived from a GFP marker co-expressed form the AAV5-shRNA vector, and PDE1B protein expression. (C) Open field exploration in mice treated with shPde1b (n = 20) or shGFP control (n = 20) virus. Left: Ambulation over the 10 min trial duration. Right: Time in the center and periphery of the open field. No difference was found between treatment groups. (D) Contextual fear memory was enhanced by PDE1B knockdown. Time spent freezing upon re-exposure to the training context is shown. shPde1b (n…

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  FIGURE 2. Effects of intra-hippocampal shRNA PDE1B knockdown on spatial memory in the Barnes Maze in mice. (A) Search strategies employed in the Barnes Maze test. Mice randomly sample escape holes first, but then quickly revert to serial sampling and finally employ spatial search strategies as training progresses. (B) Escape latencies during the 4 acquisition trials, two each day separated by a 1 min ITI, did not differ between the treatment groups. (C) The number of errors prior to the correct escape did not differ amongst the treatment groups. Both shPde1b (n = 50) and shGFP control (n = 51) virus treated mice improved within each training day, indicating normal working memory. D-G) A 2 min probe-test was conducted 24 h after the 4th acquisition trial. (D) Locomotion during probe-test did not differ between the treatment groups. (E) shPde1b treated mice made significantly less errors before approaching the correct (trained) escape hole. (F) shPde1b mice spent significantly more time in the quadrant that contained the trained escape hole than shGFP controls. (G) Proportion of mice using random, serial, and spatial sampling strategies. A larger proportion of shPde1b treated mice utilized…

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  FIGURE 3. Effect of the PDE1 inhibitor DNS-0056 on acquisition, consolidation, and retrieval of contextual memory in rats. (A) 2× trial training 60 min after p.o. administration of DNS-0056 (n = 32) or vehicle (n = 32), and subsequent 24-h memory test. DNS-0056 did not affect freezing during the acquisition of contextual fear, but significant enhancement was seen in the long-term memory test. (B) Response to foot-shock during cFC training, 60 min after a p.o. dose of DNS-0056. The drug did not affect baseline motion or shock US perception. (C) Post-trial dosing of DNS-0056 or vehicle. Freezing during the 24-h retention test is shown (n = 32 per group/time-point). Drug dosed immediately after training significantly enhanced 24-h retention of contextual fear, but no effect was seen when drug was dosed either 60 min after training, or 60 min before the memory test on day two. Mean ± s.e.m. are shown. Significant differences from vehicle control are indicated by an asterisk (∗).