Changeover from alternate to synchronous bilateral pattern of the phrenic bursts entrained by fictive locomotion in the spinal rabbit preparation.

Phrenic bursting resulting from locomotor entrainment during fictive locomotion was shown previously in high spinal preparation after nialamide-DOPA administration. The temporal evolution of the bilateral pattern of phrenic vs locomotor activity is considered here. At variance with the bilateral locomotor pattern which is always alternate (fictive stepping), the pattern on both phrenic nerves changes with time after DOPA injection: first alternate, left and right phrenic bursts become synchronous. A study of ipsilateral phrenic-locomotor phase relationships allowed to disclose the way the transition from alternate to synchronous phrenic coupling was achieved: synchronism appeared as resulting from a strong facilitation on the overlapping parts of the bilaterally alternating phrenic bursts; this phase shifting, vs the ipsilateral locomotor pattern, accounts for the transfer of phrenic bilateral coupling.