Vagal input increased the amplitudes of heart period variations at 1.5-2.5 and 6-10 cycles/min in decerebrate cats, whereas sympathetic activity played no role in generating these rhythms.
Spectral analysis was used to investigate variations of heart period in 13 decerebrate cats under different conditions of neural input to the heart. Spectral density plots in intact animals showed three well-defined peaks: P1 (1.5-2.5 cycles/min), P2 (6-10 cycles/min), and P2 (respiratory frequency). In the presence of sympathetic input only the amplitudes of all peaks were decreased; when only vagal input was present the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were found to be significantly correlated with the mean heart period under the condition of vagal control only. It is concluded that P3 is related to sinus arrhythmia and that P1 and P2 may be related to spontaneous rhythms that are an intrinsic feature of the dynamic regulation of heart period by the vagus system. Sympathetic activity plays no role in the genesis of these rhythms.
Chess et al. (Sat,) conducted a other in decerebrate cats (n=13). Different conditions of neural input (sympathetic vs vagal) vs. Intact animals / no neural input was evaluated on Variations of heart period (spectral density peaks). Vagal input increased the amplitudes of heart period variations at 1.5-2.5 and 6-10 cycles/min in decerebrate cats, whereas sympathetic activity played no role in generating these rhythms.