In The Regulation Of Raphe Nuclei On Respiratory Movement

Raphe nucleus has been described as a midline structure located in the midline region and adjacent reticular formations of the brainstem and mesencephalon. It has been well documented that in mammals the medullary raphe subnuclei were involved in respiratory control, sleeping and wakefulness, cardiovascular function and various other physiological functions. In this study, several issues concerning the respiratory regulation of this structure were systematically addressed, such as the respiratory responses to electrical and chemical stimulation of three caudal medullary raphe subnuclei, the involvement of GABAergic and serotonergic neurons in raphe's respiratory control, and the involvement of purinergic neurotransmission in respiratory control via the raphe nuclei. Based on these studies, we concluded that the medullary raphe subnuclei are involved in the control of respiratory frequency and tidal volume, and that different raphe subnuclei are responsible for facilitation or inhibition on respiratory movements respectively. The raphe subnuclei exerted differential effects on respiration through GABAergic or serotonergic descending projections to spinal phrenic motor nucleus, and the ATP-P2X mediated neurotransmission could influence respiration by way of the medullary raphe subnuclei.1. Electrical and chemical stimulation of raphe subnucleiThe first part of this study was devoted to determining the effects of electrical or chemical stimulation of the medullary raphe nuclei on respiratory movements. Experiments were performed on adult Wistar rats anesthetized with ketamine and xylazine. The animals breathed spontaneously and the respiratory movement was recorded with an abdominal pneumograph. Train pulse stimuli (100 Hz, 100-200 pulses, 0.2 msec pulse width, 10-30μA) were applied to the regions of the medullary raphe nuclei. Stimulation of the RM produced intensity-dependent inhibitory response in respiratory movements both in terms...