Electrophysiological characteristics of amygdaloid central nucleus neurons in the awake rabbit.

Considerable evidence suggests that the amygdaloid central nucleus (ACE) may contribute importantly to autonomic regulation, possibly via direct ACE projections to the brainstem. Lacking, however, have been comprehensive data concerning the electrophysiological characteristics of ACE neurons. The present experiment was therefore undertaken in order to characterize the spontaneous activity and sensory-evoked responses of ACE neurons in the conscious rabbit. Particular attention was given to the identification, via antidromic activation, and characterization of those ACE neurons which project to the lower brainstem. Single-unit recordings were obtained from 100 histologically verified ACE neurons. Most of these, including all brainstem projection neurons, discharged at very low spontaneous rates and were unresponsive to the presentation of auditory, visual and somatic stimuli. Based upon spontaneous activity and sensory-evoked responses, the activity of other ACE neurons appeared to conform to one of several profiles. These included neurons showing increased activity to the presentation of all sensory stimuli, and neurons showing activity that was spontaneously entrained with the respiratory cycle. These data indicate the heterogeneous nature of ACE neuronal activity, and provide a basis for the comparison of additional experiments which concern the electrophysiological characteristics of the ACE.