Cardiovascular and respiratory relationships with neuronal discharge in the central nucleus of the amygdala during sleep-waking states

We examined state-related relationships of neuronal discharge in the central nucleus of the amygdala (ACE) with cardiac and respiratory patterning. ACE cell discharges correlated with cardiac and respiratory timing, arterial pressure, and several respiratory parameters in undrugged, freely moving cats during waking, quiet sleep, and rapid eye movement sleep. Phasic discharge with the cardiac or respiratory cycle was examined using cross-correlation histograms. Of 80 cells in 8 cats, 24% showed a timing relationship with the cardiac or respiratory cycle, i.e., a tendency to discharge with each cardiac R-wave or with each breath, 12% with the cardiac cycle, and 14% with the respiratory cycle (2 cells showed both). All timing relationships were state dependent, usually observed in only one sleep-waking state per cell. Over half the cells showed a significant Pearson's r rate correlation with respiratory period or arterial pressure. Two-thirds of the cells showing arterial pressure correlations also correlated with respiratory period. A substantial proportion of ACE cells thus shows a state-dependent modulation of discharge rate and pattern by cardiovascular and respiratory variables. Rate and timing relationships were mutually exclusive within states, suggesting a state-dependent functional differentiation within the ACE.