The roles of the parabrachial nucleus at the consciousness-unconsciousness switch: as a vocalization-respiration mode switch

Abstract

The Parabrachial nucleus complex (PB), consisting of the lateral parabrachial nucleus, medial parabrachial nucleus, and Kolliker-Fuse nucleus, is known as a respiratory modulating center. We examined how the PB participates in respiratory modulation using pons-medulla-spinal cord preparations obtained from 0-4-days old rats. First, the effects of PB electrical stimulation on C4 ventral nerve inspiratory activity were examined. The electrical stimulation induced a transient depression or termination in C4 inspiratory activity. This inhibition of C4 inspiratory activity was greatly reduced by perfusion of NMDA antagonists and the inhibition was blocked by perfusion of a GABAA-antagonist. Inspiratory-expiratory (I-E) neurons were mainly recorded in the PB. In the medulla, the inspiratory neurons received IPSPs and the expiratory neurons received EPSPs when PB was stimulated. It seems that PB is an active inspiratory-expiratory phase-switching system. In conclusion, PB is involved in the inspiratory termination in neonatal period; and PB might be an active mode switching system that switches from unconscious respiration to conscious vocalization.