Differential involvement of cholinergic and beta-adrenergic systems during acquisition, consolidation, and retrieval of long-term memory of social and neutral odors

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Acetylcholine and norepinephrine have been implicated during different kinds of social recognition that involves olfactory memory formation. For example, blockade of muscarinic and beta-adrenergic receptors has been shown to impair short-term memory of both socially relevant as well as of neutral odors. However, previous studies have not explicitly compared the role of cholinergic and adrenergic modulation in long-term memory for socially relevant odor vs. incidental odor stimuli. In this work, we studied the function of muscarinic and beta-adrenergic receptors during acquisition and/or consolidation of a novel odor and during the retrieval of a familiar odor. The effects of systemic injections of scopolamine and propranolol, before and after presentation of estrous urine odor or mint odor, were evaluated by a long-term odor habituation task. The results demonstrated that scopolamine disrupts memory acquisition and/or consolidation of mint odor, and did not have any effect during retrieval of mint odor memory. Conversely, scopolamine disrupts memory consolidation and retrieval of estrous odor, depending on the dose applied. Propranolol injections have no effect on acquisition or consolidation for mint or estrous odor, but disrupt memory retrieval of familiar odor regarding their social/sexual or neutral content. These results demonstrate that muscarinic receptors are required differentially during long-term odor memory formation and for familiar odor recognition depending on the socially relevant content of the stimulus. Furthermore, the beta-adrenergic system could play an important role in memory recognition for familiar odors, regardless of the sexual/social or neutral content of the stimuli.