WE have developed in new-born mice a ventral tilted-horizontal slice p
reparation for pontine stimulation and recording of spontaneous respir
atory-like rhythmic trains of glutamatergic excitatory postsynaptic po
tentials (EPSPs) in medullary neurons. Electrical stimulations (10-50
Hz for 100-500 ms) of the caudal pontine reticular formation triggered
a burst of EPSPs, recycling of the rhythmic activity and persistent i
ncrease of the rhythmic behaviour. These results identify a ventral po
ntine pathway that promotes rhythm generating mechanisms in the medull
a and probably derives from a population of lateral reticular neurons
identified in the embryonic hindbrain and eliminated after inactivatio
n of the early developmental gene Krox-20.