Serotonergic effects on hypoglossal neural activity and reflex responses.

We determined the effects of serotonin (5HT; 6 concentrations ranging from 0.005 to 500 microM) pressure microinjection into the hypoglossal (XII) motor nucleus (100-500 nl; pH = 7.2-7.

Activity of respiratory neurons during hypoxia in the chemodenervated cat.

Exposure of anesthetized paralyzed vagotomized peripherally chemodenervated cats to hypoxia results in initial depression and subsequent loss of the phrenic neurogram. To determine whether hypoxic respiratory depression results from the inhibition of respiratory premotor neurons by bulbospinal neurons of the Bötzinger complex (Böt-E neurons), extracellular recordings were made of dorsal and ventral respiratory group bulbospinal inspiratory neurons and Böt-E neurons during acute hypoxic hypoxia. All neurons recorded decreased firing rate during hypoxia.

Excitation of upper cervical inspiratory neurones by vagal stimulation in the cat.

The responses of 57 upper cervical inspiratory neurones to single shock stimuli applied to the ipsilateral cervical vagus nerve were recorded using peri-stimulus histograms in 19 cats. Many (47%) of the histograms showed a late latency (17.9 +/- 3.