Passive rotation-induced theta rhythm and orientation homeostasis response.
Rhythmic oscillatory activities at the theta frequency (3-12 Hz) have long attracted attention, as they have been implicated in diverse brain functions. There are two kinds of hippocampal theta rhythms: Type 1 is an atropine-resistant noncholinergic theta rhythm, and Type 2 is an atropine-sensitive cholinergic theta rhythm. However, it has not yet been determined whether the theta rhythm generated during passive whole-body rotation is of Type 1 or 2. To clarify this issue, we investigated passive whole-body rotation-induced theta rhythm using C57BL/6J normal and atropine-treated mice. The results demonstrated that atropine [50 mg/kg, intraperitoneally (i.p.)], a cholinergic antagonist, abolished the theta rhythm generated during passive whole-body rotation. Therefore, the passive whole-body rotation-induced theta rhythm is an atropine-sensitive Type 2 theta rhythm. In addition, we found that blocking cholinergic receptors using atropine resulted in the loss of the orientation homeostasis response, which is a circling behavior in the direction opposite to that of the rotating circular treadmill that is generated to maintain a constant orientation. These results suggest that atropine-sensitive Type 2 theta rhythm can be generated by a passive rotation-induced vestibular sensory signal and may be necessary for spatial orientation homeostasis response behavior.
Shin
Jonghan
J
Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon 405-760, Republic of Korea. jhshin@gachon.ac.kr
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003624:Darkness; D004567:Electrodes, Implanted; D004569:Electroencephalography; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009068:Movement / Q000187:drug effects / Q000502:physiology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009949:Orientation / Q000502:physiology*; D012399:Rotation; D013826:Theta Rhythm / Q000187:drug effects; D014796:Visual Perception / Q000187:drug effects / Q000502:physiology
D018727:Muscarinic Antagonists; D001285:Atropine