Development of thyrotropin-releasing hormone and norepinephrine potentiation of inspiratory-related hypoglossal motoneuron discharge in neonatal and juvenile mice in vitro.
1. The ontogeny of thyrotropin-releasing hormone (TRH) and norepinephrine (NE) potentiation of inspiratory-related hypoglossal (XII) motor nerve discharge was studied in medullary slices from P0-3, P7, and P11-14 mice that retain functional networks for respiration. 2. TRH, applied locally to the XII motor nucleus, had no effect on XII inspiratory burst amplitude in slices from P0-3 mice. By P7 there was significant potentiation of burst amplitude that increased more than three-fold by P11-14. NE applied to the XII nucleus produced significant potentiation in all age groups. Potentiation increased developmentally with the largest increase occurring between P0-3 and P7. 3. Thus catecholamine and TRH modulation of inspiratory-related XII nerve activity increases during the first two weeks of life; the potentiating effects of NE appear prior to those of TRH. 4. With rhythmically active, transverse medullary slices from mice up to 2 wk of age, it is now possible to study the development of XII motoneuron modulation as it relates to respiratory control of the upper airway.
Funk
G D
GD
Department of Physiological Science, University of California, Los Angeles 90024-1527.
Smith
J C
JC
Feldman
J L
JL
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D046508:Culture Techniques; D007002:Hypoglossal Nerve / Q000502:physiology*; D001239:Inhalation / Q000502:physiology*; D008526:Medulla Oblongata / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009046:Motor Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013973:Thyrotropin-Releasing Hormone / Q000502:physiology*
D013973:Thyrotropin-Releasing Hormone; D009638:Norepinephrine