A ventral pontine pathway promotes rhythmic activity in the medulla of neonate mice.

We have developed in new-born mice a ventral tilted-horizontal slice preparation for pontine stimulation and recording of spontaneous respiratory-like rhythmic trains of glutamatergic excitatory postsynaptic potentials (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 increase of the rhythmic behaviour. These results identify a ventral pontine pathway that promotes rhythm generating mechanisms in the medulla and probably derives from a population of lateral reticular neurons identified in the embryonic hindbrain and eliminated after inactivation of the early developmental gene Krox-20.