Abstract
Numerous studies have suggested that caudal raphe nuclei may play some roles in respiration. However, details of the role of the raphe nuclei in controlling of respiration have not been clarified. We have previously reported that respiratory neurons are present in medullary raphe nuclei. The present study was undertaken to examine the effects of hypercapnia on the respiratory neurons of medullary raphe nuclei. The experiments were performed on decerebrate, paralyzed, vagotomized and artificial ventirated rat. Extracellular recordings were made from neurons having firing patterns related to phrenic nerve discharge in the midline medullary tegmentum. We recorded mainly Inspiratory (I) throughout neurons which firerd throughout the I phase in the raphe obscurus and pallidus. They were tested changes in neuronal discharges when the ventilator was stopped (during 8-24 sec; end-tidal CO2 levels were raised from 5±0.4 to 8±0.3%). Most of the neurons examined responded to hypercapnea in the neuronal discharge. But some neurons examined did not respond. These results suggest that the midline caudal raphe nuclei are involved in central chemoreception. [J Physiol Sci. 2006;56 Suppl:S137]
