Distribution of Activating Neurons in Medulla Oblongata by Stimulation of the Vagus Nerve

Electrical activity of efferent vagal fibres and dorsal nucleus of the vagus during reflex bradycardia in the cat

“…This finding is consistent with the low counts of myelinated efferent fibres in cardiac branches of the cat (Agostoni et al 1957), and implies a similarly small number of cells of origin. This could explain the failure of others to record evoked potentials in the DNV following peripheral vagal stimulation (Urabe & Tsubokawa, 1960;Porter, 1963) and also the scarcity of axonal degeneration seen in cardiac vagal branches following lesions in the DNV (Calaresu & Cottle, 1964). On the other hand, the evidence does not exclude the possibility that, although some motor fibres to the heart may originate in it, the DNV is not the cell station of the cardio-inhibitory component of the vagus nerve.…”

Effects on heart rate of electrical stimulation of medullary vagal structures in the cat

“…A second explanation for the failure to produce bradycardia by stimulation of the dorsal nucleus could be that the cardiomotor fibres of the vagus do not originate in it. This possibility is supported by the failure to record evoked potentials in the nucleus during stimulation of the peripheral nerve (Urabe & Tsubokawa, 1960;Porter, 1963) and the paucity of cells of the middle third of this nucleus which showed increased activity during reflex bradycardia (Calaresu & Pearce, 1964). It is known that the DNV does not receive any direct connexions from primary cardiovascular afferents (Cottle, 1964).…”

“…To this evidence has recently been added the observation of axonal degeneration in the vagus nerve following selective ablation of the dorsal nucleus in the cat (Calaresu & Cottle, 1964). Although Anderson & Berry (1956) have described evoked potentials in the region of the dorsal nucleus of the vagus following stimulation of the whole peripheral nerve, two recent studies in which more refined methods were used, including histological demonstration of recording electrode positions, have failed to confirm this finding (Urabe & Tsubokawa, 1960;Porter, 1963). Furthermore, unit discharges in the dorsal nucleus showing increased activity during reflex bradycardia were only rarely encountered with extracellular micro-electrodes (Calaresu & Pearce, 1964).…”

Origin of cardiomotor fibres in the dorsal nucleus of the vagus in the cat: a historical study

“…Urabe & Tsubokawa (1960) and Porter (1963) have failed to record evoked potentials in the DNV following stimulation of the peripheral vagus; Anderson & Berry (1956), with a less refined technique, have claimed they could do so.…”