Modulation of the respiratory rhythm generator by the pontine noradrenergic A5 and A6 groups in rodents.

The aim of the present review is to summarise available studies dealing with the respiratory control exerted by pontine noradrenergic neurones in neonatal and adult mammals. During the perinatal period, in vitro studies on neonatal rodents have shown that A5 and A6 neurones exert opposite modulations onto the respiratory rhythm generator, inhibitory and facilitatory respectively, that the anatomical support for these modulations already exists at birth, and that genetically induced alterations in the formation of A5 and A6 neurones affect the maturation of the respiratory rhythm generator, leading to lethal respiratory deficits at birth. The A5-A6 modulation of the respiratory rhythm generator is not transient, occurring solely during the perinatal period but it persists throughout life: A5 and A6 neurones display a respiratory-related activity, receive inputs from and send information to the medullary respiratory centres and contribute to the adaptation of adult breathing to physiological needs.