Hippocampal RSA (theta), apnea, bradycardia and effects of atropine during underwater swimming in the rat.

Hippocampal RSA (theta), neocortical EEG, and heart rate were recorded during surface and underwater swimming in the rat. RSA was present with slightly reduced frequency during the apnea, bradycardia, and vibrissae arrest associated with under water swimming. Atropine sulfate (50 mg/kg) blocked bradycardia did not affect RSA. Contrary to previous suggestions, no causal relation was found between RSA and respiration, heart rate, or vibrissae movement. The study supports the view that RSA is related to the neural control of voluntary movement. It is suggested that the slight reduction in RSA frequency during underwater swimming may be part of an oxygen conservation process.