Apneusis and apnea after parabrachial or Kölliker-Fuse N. lesion; influence of wakefulness.

Comparisons were made between the effects of bilateral lesions of either the nucleus parabrachialis medialis (NPBM) or the Kölliker-Fuse (KF) nuclei in bivagotomized, spinalized and immobilized cats. In a first group animals were electrolytically decerebrated; in a second group animals were locally anaesthetized and atraumatically restrained (semi-chronic encéphale isolé preparation). Lesions resulted in: (1) a marked increase in TI (apneusis); (2) 50--80% decrease in amplitude of the integrated phrenic discharge (IPD); (3) variable lengthening, of TE. Following KF lesion, effects were significantly larger on TE in the decerebrate group, and on TI in the encéphale isolé group. In the encéphale isolé group awakening reduced TE and TI and brought them close to their prelesion values following both NPBM and KF lesion; on the other hand light sleep induced by pentobarbital led to expiratory apnea after KF lesion and reduced IPD amplitude to zero after NPBM lesion. It is proposed that the onset, tonic drive and cut off of the I discharge are normally controlled by three differently weighted influences originating from NPBM, KF and reticular formation respectively.