Induction of Fos-like protein in neurons of the medulla oblongata after electrical stimulation of the vagus nerve in anesthetized rabbit.

Antibodies against the c-fos protein product Fos were used to map the first- and higher-order neurons in the rabbit medulla oblongata after electrical stimulation of the vagus nerve. Fos immunoreactivity appeared bilaterally except in the nucleus tractus solitarii. Seven areas were labeled: the nucleus tractus solitarii, the area postrema, the subnucleus lateralis caudalis magnocellularis medullar oblongata, the lateral reticular nucleus, the ambiguus nucleus, the dorsal part of the spinal trigeminal nucleus, the nucleus reticularis lateralis, the lateral border of the external cuneatus nucleus, the medial part of the inferior olivary nucleus (subnucleus beta). The last two areas have never been visualized with conventional tracing techniques and may represent higher-order neurons connected to visceral vagal pathways. No labeling was observed in the nodose ganglion.