Fig. 7.

V0 neurons ensure bilaterally synchronized and balanced C4 outputs in vitro. a Spontaneous fluorescence (ΔF/F) changes of the left (L) and right (R) facial motor nucleus (VII, top traces) and electrophysiological activities of the left and right C4 motor root (bottom traces) showing phased (*) rhythmic bouts of activity in wild-type preparations. b Histogram of the normalized amplitudes of synchronous left (L C4) and right (R C4) phrenic motor bursts showing their balanced amplitudes. c In Dbx1 ^cre ; Robo3 ^lox/lox preparations, the left (black arrowheads) and right (white arrowheads) bouts of VII activity were found de-synchronized but still phased (vertical lines) with bilaterally synchronized bouts of activity of the C4 motor roots. Note the higher amplitude of the burst on the C4 root ipsilateral (ip.C4) to the active VII when compared to that recorded from the contralateral side (Co.C4). d Histogram of the normalized amplitudes of synchronous ip.C4 and Co. C4 showing the reduced amplitude of the latter. e Dbx1 ^cre ; Robo3 ^lox/lox mutant preparations, at P0, show an aggravated unbalance of the amplitudes of the synchronous bouts of activity of the left and right C4. f Histogram of the normalized amplitudes of yet synchronous ip.C4 and Co. C4 bursts of activity showing the much greater amplitude of ip.C4 relative to Co. C4 bursts suggesting an almost complete loss of commissural connectivity. Phased activity events (*) were still detected occasionally in Dbx1 ^cre ; Robo3 ^lox/lox preparations at both E15.5 (17/144 bursts from four preps) and P0 (6/79 bursts from four preps) either caused by fortuitous phasing of the independent left and right motor drives or by a yet unidentified source of synchronous bilateral drives to the rhythm generator. ***p < 0.001