Location of bulbospinal neurons and of laryngeal motoneurons within the nucleus ambiguus of the rat and cat by means of retrograde fluorescent labelling.

The location of bulbospinal neurons within the nucleus ambiguus with respect to laryngeal motoneurons has been studied by means of retrograde fluorescent neuronal markers (True Blue and Diamidino Yellow in rats, and Fast Blue and Diamidino Yellow in cats). One marker was injected into the cervical spinal cord, and the other into the intrinsic laryngeal muscles. Afterwards, the precise location of each neuronal pool was observed with the fluorescent microscope. The bulbospinal neurons in the rostral part of the nucleus were located ventrolaterally with respect to motoneurons, both in cats and rats; at more caudal levels of the nucleus the bulbospinal neurons were arranged ventromedially and ventrolaterally with respect to motoneurons in cats, and around the motoneurons in rats.