BIDIRECTIONAL ELECTRICAL COUPLING BETWEEN INSPIRATORY MOTONEURONS IN THE NEWBORN MOUSE NUCLEUS AMBIGUUS

Some spinal and brain stem motoneurons are electrically coupled in the early postnatal period. To test whether respiratory motoneurons in th e brain stem are electrically coupled, we performed single and dual wh ole cell patch recordings from presumptive motoneurons 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 pairs of neurons showed evide nce of bidirectional electrical coupling. Impulse activity in one cell elicited small spikelets in the other and hyperpolarization of one ce ll led to hyperpolarization of the other with a coupling ratio (Delta v(2):Delta v(1)) of 0.03-0.14. We conclude that inspiratory ambiguus m otoneurons in the newborn mouse brain stem are bidirectionally electri cally coupled, which may serve to transmit or coordinate signals, chem ical or electrical.