Protein tyrosine phosphatase receptor type R deficient mice exhibit increased exploration in a new environment and impaired novel object recognition memory

•PTPRR isoforms are expressed throughout the mouse brain.•Ptprr knockout mice display normal olfactory bulb-related basal smell function.•In Ptprr knockout mice spatial and fear-associated learning are not affected.•Ptprr knockout mice have impaired novel object recognition memory.•Ptprr knockout mice demonstrate increased exploration in a new environment. Mouse gene Ptprr encodes multiple protein tyrosine phosphatase receptor type R (PTPRR) isoforms that negatively regulate mitogen-activated protein kinase (MAPK) signaling pathways. In the mouse brain, PTPRR proteins are expressed in cerebellum, olfactory bulb, hippocampus, amygdala and perirhinal cortex but their precise role in these regions remains to be determined. Here, we evaluated phenotypic consequences of loss of PTPRR activity and found that basal smell was normal for Ptprr−/− mice. Also, spatial learning and fear-associated contextual learning were unaffected. PTPRR deficiency, however, resulted in impaired novel object recognition and a striking increase in exploratory activity in a new environment. The data corroborate the importance of proper control of MAPK signaling in cerebral functions and put forward PTPRR as a novel target to modulate synaptic processes.