NONVAGAL REFLEX APNEA IN THE NEWBORN KITTEN AND DURING THE EARLY POSTNATAL-PERIOD

The aim of this work was to study the nonvagal mechanisms which might induce apneic reflexes in kittens. Experiments were performed on spont aneously breathing animals (19 kittens at different postnatal ages). A nimals were anesthetized (halothane) or decerebrated by transcollicula r section of the brainstem. Weakly nociceptive cutaneous stimulations and various oral stimulations were administered in all animals. In 10 kittens, one of the lingual nerves was stimulated electrically. In 3 d ecerebrate kittens the effects of serotonin on respiratory activity an d on muscles innervated by the hypoglossal nerve were studied. All the stimulations produced apneas of variable duration, and expiratory rei nforcement was associated with activation of pretracheal muscles. Simi lar effects were observed after applying serotonin to the floor of the 4th ventricle. Thus serotonin may be involved in the mechanisms that cause some apneas.