抄録
The midline raphe nuclei may be involved in the control of respiration. Stimulation of the caudal raphe regions, including raphe obscurus (RO), pallidus (RP) and magnus (RM), causes a change in respiration. These regions contain serotonergic cells. However, the raphe nuclei also contain non-serotonergic neurons. This study was undertaken to investigate firing patterns and spinal projections of respiratory neurons in medullary raphe nuclei of cat, and examined whether these respiratory neurons were serotonergic or not. Extracellular spikes of 28 single respiratory neurons were recorded in midline medullary tegmentum in Nembutal anesthetized cats. A total of 28 respiratory neurons was recorded in the raphe obscurus, pallidus and magnus. The cells were classified as Late-inspiratory (I) (Late-I, n=5), inspiratory-expiratory (E) phase-spanning (I-E PS, n=5), E-I phase-spanning (E-I PS, n=8), expiratory-decrementing (E-DEC, n=4), E-frequency modulated (n=3), inspiratory-constant (I-CON, n=3) based on their firing pattern in relation to the phase of respiration. Out of the 18 respiratory neurons were tested for antidromic activation from the ventrolateral quadrant of the C4-5 spinal cord, two E-frequency modulated, one E-DEC and one E-I PS neuron were antidromically activated with the latencies that corresponded to axonal conduction velocities of 12.8–27.3 m/s. These results suggest that some non-serotoninergic respiratory neurons of the caudal raphe nuclei transmit respiratory activity to the spinal cord. [J Physiol Sci. 2008;58 Suppl:S116]
