Morris water task impairment and hypoactivity following cysteamine-induced reductions of somatostatin-like immunoreactivity

The effects of cysteamine-induced reductions of somatostatin-like immunoreactivity (SLI) on spatial learning, passive avoidance, and locomotor activity were examined in adult Sprague-Dawley rats. Cysteamine hydrochloride (100 mg/kg, s.c.) produced 54% and 50% reductions in SLI in cortex and hippocampus, respectively, and impaired escape latencies and spatial probe behavior in the Morris water task. Although cysteamine-treated rats displayed hypoactivity in the activity boxes, their swim speed in the Morris water task was unaffected. Cysteamine did not impair passive avoidance retention when administered immediately following training or prior to daily retention testing. These results suggest a role for somatostatin in spatially-mediated behaviors in rats.