Muscarinic receptors activity in the perirhinal cortex and hippocampus has differential involvement in the formation of recognition memory

► Scopolamine injections into perirhinal cortex or the hippocampus disrupted short-term object recognition memory. ► Scopolamine injections into perirhinal cortex disrupted long-term object recognition memory. ► Scopolamine injections in the hippocampus did not affect long-term object recognition memory. In this work we probed the effects of post-trial infusions of the muscarinic receptor antagonist scopolamine on object recognition memory formation. Scopolamine was infused bilaterally immediately after the sample phase in the perirhinal cortex or dorsal hippocampus and animals were tested for short-term (90min) or long-term (24h) memory. Results showed that scopolamine impaired short-term memory when injected in either the perirhinal cortex or hippocampus. Nevertheless, scopolamine disrupted long-term memory when administrated in the perirhinal cortex but not when applied in the hippocampus. Long-term memory was unaffected when scopolamine was infused 160min after the sample phase or 90min before test phase. Our data indicate that short-term recognition memory requires muscarinic receptors signaling in both the perirhinal cortex and hippocampus, whereas long-term recognition memory depends on muscarinic receptors in the perirhinal cortex but not hippocampus. These results support a differential involvement of muscarinic activity in these two medial temporal lobe structures in the formation of recognition memory.