Infrasonic stimulation induced Fos expression in medullary catecholaminergic neurons in rats

To clarify the effects of infrasound on the medulla, catecholaminergic neurons in the medulla expressing Fos were investigated in the rats by immunohistochemical method. After exposure to infrasound (8Hz, 120dB) for 2 hours, animals were sacrificed and sections of the medulla were stained immunohistochemically for Fos and tyrosine hydroxylase (TH), Many Fos-like immunoreactive neurons were found in the nucleus tractus solitarii (NTS) and Ventrolateral medulla (VLM) at the middle and caudal levels of medulla, only afew of them scattered in the reticular formation between NTS and VLM. Some Fos immunoreactive neurons were also labeled with TH. These results indicated that medulla was sensitive to infrasonic stimulation and some medullary catecholaminergic neurons might be involved in the responses to the stress produced by infrasound.