The activity of catecholaminergic neurons in the hypothalamus and the medullary visceral zone (MVZ) in rats in response to restraint water-immersion stress (RWIS) was measured by use of dual Fos and tyrosine hydroxylase (TH) immunohistochemistry. In RWIS rats Fos immunoreactive (Fos-IR) nuclei dramatically increased in the paraventricular nucleus (PVN), the supraoptic nucleus (SON), the dorsal motor nucleus of the vagus (DMV), the nucleus of the solitary tract (NTS), the area postrema (AP), and the ventrolateral medulla (VLM). A small number of TH-immunoreactive (TH-IR) and Fos/TH double-labeling neurons in the PVN, and their absence from the SON, were observed in both RWIS and nonstressed rats. More TH-IR neurons were observed in the MVZ of RWIS rats than in nonstressed rats. In RWIS and nonstressed rats, the percentage of Fos-IR nuclei in TH-IR neurons was 38.0 and 14.3% in the DMV, 34.4 and 9.7% in the NTS, 18.6 and 4.5% in the AP, and 45.7 and 18.9% in the VLM, respectively. In conclusion, catecholaminergic neurons in the MVZ are involved in the response to RWIS; although the PVN and SON also participate in the response to RWIS, the mechanism is not via catecholaminergic neurons.

The present study was to investigate whether there are functional connections between the hypothalamic supraoptic nucleus (SON) and the stomach, which is the case with the paraventricular nucleus. The rats were divided into four groups. Group I: the neuronal discharge was recorded extracellularly in the NTS, DMV or SON before and after cold physiological saline (4°C) was perfused into the stomach and effused from the duodenum. Group II: the rats were stimulated as for Group I and c-Fos expression in NTS, DMV and SON was examined. Group III: the control to Group II. Group IV: gastric motility was recorded continuously before and after microinjection of L: -Glu into the SON. In Group I, the discharge frequency increased in all the three nuclei, while in Group II, Fos expression in NTS, DMV and SON was, respectively, greater than that of Group III. In Group IV, microinjection of L: -Glu (5 nmol) into SON significantly inhibited gastric motility. These data suggest there are functional connections between SON and stomach.

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