RAPID COMMUNICATION Bidirectional Electrical Coupling Between Inspiratory Motoneurons in the Newborn Mouse Nucleus Ambiguus

Rekling, Jens C. and Jack L. Feldman. Bidirectional electrical was cut on a Vibratome. The rostral cut was placed 150 mm caudal to the rostral boundary of the compact formation of nucleus ambicoupling between inspiratory motoneurons in the newborn mouse nucleus ambiguus. J. Neurophysiol. 78: 3508–3510, 1997. Some guus. The preparation was transferred to a 0.2-ml recording chamber and was superfused 3 ml/min with preheated (28.07C) oxygenspinal and brain stem motoneurons are electrically coupled in the early postnatal period. To test whether respiratory motoneurons in ated (95% O2-5% CO2, pH 7.4) artificial cerebrospinal fluid (aCSF). The aCSF solution contained (in mM) 130 NaCl, 5.4 the brain stem are electrically coupled, we performed single and dual whole cell patch recordings from presumptive motoneurons KCl, 0.8 KH2PO4, 26 NaHCO3, 30 glucose, 1 MgCl2 , and 0.8 CaCl2 . in the nucleus ambiguus in a rhythmically active brain stem slice from newborn mice. Two of eight (25%) biocytin-injected neurons showed dye-coupling and 4 of 11 (36%) of intracellularly recorded XII nerve recordings pairs of neurons showed evidence of bidirectional electrical coupling. Impulse activity in one cell elicited small spikelets in the Rhythmic respiratory-related motor output was recorded by a other and hyperpolarization of one cell led to hyperpolarization of suction electrode placed on a hypoglossal XII rootlet. Nerve activthe other with a coupling ratio (DV2 :DV1) of 0.03–0.14. We conity was amplified by a GRASS amplifier and filtered at 3 Hz to 1 clude that inspiratory ambiguus motoneurons in the newborn kHz. Sixty hertz noise was eliminated by a HumBug (Quest Scienmouse brain stem are bidirectionally electrically coupled, which tific) and rectified nerve activity was integrated (RC circuit, time may serve to transmit or coordinate signals, chemical or electrical. constant 50 ms).