Heart rate surges during REM sleep are associated with theta rhythm and PGO activity in cats

Rapid eye movement (REM) sleep is characterized by periods of profound card iac autonomic activation evident in heart rate surges in humans and canines . Our goals were to determine whether or not the heart rate surge phenomeno n occurs in cats and to characterize concurrent central nervous system acti vity. Cortical and hippocampal electroencephalogram, electromyogram, electr ooculogram, pontogeniculooccipital (PGO) waves, subcutaneous electrocardiog ram, and respiration were recorded. Bouts of sinus tachycardia lasting grea ter than or equal to 3.5 s achieved a rate of 210 beats/min and were presen t predominantly during REM sleep. Heart rate during the surges rose an aver age of 26.4% from 132.5 +/- 2.0 beats/min before the surge to 167.5 +/- 2.6 beats/min (P < 0.001) and returned to 130.7 +/- 2.6 beats/min (P < 0.001). The heart rate surges were invariably accompanied by increased incidence a nd frequency of hippocampal theta waves and increased PGO wave frequency an d incidence of PGO wave clusters and eye movement clusters. The occurrence of surges was dramatically reduced from 0.11 +/- 0.03 to 0.01 +/- 0.01/15 s of REM sleep (P = 0.02) by atenolol (0.6 mg/kg iv), indicating that the ph enomenon is beta(1)-adrenergically mediated. These findings suggest a coupl ing between central activation of cardiac sympathetic nerves and the genera tion of hippocampal theta waves and PGO activity.