Abstract
A number of studies have shown that stimulation of the medullary raphe nuclei, consisting of the raphe obscurus, raphe pallidus and raphe magnus, produces inhibitory or excitatory effects on respiration. However, details of the role of the raphe nuclei in controlling of respiration have not been clarified. Previously, we showed that respiratory neurons existed in the medullary raphe nuclei of cats and rats, and that electrical stimulation of the recording sites of these neurons caused a change in respiratory activity. The present study was undertaken to investigate the firing patterns, localization and spinal projection of respiratory neurons in the medullary raphe nuclei of rabbits. The extracellular spikes of single respiratory neurons in the midline medullary tegmentum of urethane-anesthetized and spontaneously breathing rabbits were explored. Expiratory (E), inspiratory (I), late-I, I-frequency modulated, I-E phase-spanning and E-I phase-spanning neurons, based on the relation of their firing to the phase of respiration were recorded. They were located in the raphe magnus, obscurus and pallidus. They were tested for projections to the spinal cord by antidromic electrical stimulation. Some of E neurons were projecting to the spinal cord. These results suggest that medullary raphe nuclei may take part in control of respiration in rabbits. [Jpn J Physiol 54 Suppl:S109 (2004)]
