Neural activity and bodily functions are inherently rhythmic and related to each other. Hippocampal sharp-wave ripples (SPW-Rs) and dentate spikes (DSs) supporting memory consolidation are most abundant during sleep, especially during non-rapid-eye-movement (NREM) sleep. They also seem to aggregate to a certain phase of the breathing cycle during natural sleep in mice. Here, we aimed to study if the interhemispheric synchrony of SPW-Rs and DSs is affected by neural and bodily state. We recorded dorsal hippocampal local-field potentials and respiration for several hours under urethane anesthesia in adult male Sprague-Dawley rats. For a subset, we injected 50 mg/kg atropine i.p., to antagonize muscarinic cholinergic receptors. Our results indicated a decrease in respiration rate preceding the start of SPW-R bouts. This was observed during urethane alone and after atropine injection. SPW-Rs that took place specifically during slow breathing were more often bilateral than those recorded during NREM sleep -like state overall. On the opposite, atropine decreased the interhemispheric synchrony of SPW-Rs compared to urethane alone. DSs were less bilateral during REM sleep -like state than during NREM sleep -like state and, consistently, atropine increased interhemispheric synchrony of DS compared to urethane alone. Together these results suggest that the level of interhemispheric synchrony in the hippocampus fluctuates according to both central and autonomic nervous system state. Further studies could address the effects of vagal tone on hippocampal memory replay and memory consolidation.