K(-STEM PREPARATION OF THE NEWBORN RAT()CHANNELS OF EXPIRATORY NEURONS IN THE BRAIN)

SINGLE channel activity of expiratory neurones was studied in outside- out recordings. Expiratory neurones were identified in the ventrolater al region of the in vitro isolated brain stem-spinal cord preparation of newborn rats in cell-attached and whole-cell configurations by thei r pattern of firing related to phrenic motor output. Three potassium ( K+) channels of 10, 30 and 70 pS exhibited steady-state activity durin g long voltage commands (up to 5 min) and could be found associated to gether in the same patches. The 30 pS channel showed voltage dependenc y, being most active at small depolarizations. The 70 pS channel showe d little activity with < 1% of openings per sample time and 1 mM tetra ethylammonium (TEA) sensitivity. At similar concentrations, the discha rge of the phrenic nerve was also altered, as shown by the increase of the respiratory frequency and a tonic discharge. The association of t hese K+ channel types on the same patches may be specific of respirato ry neurones and could contribute to their bursting activity.