Oxytocin and Vasopressin Involved in Restraint Water-Immersion Stress Mediated by Oxytocin Receptor and Vasopressin 1b Receptor in Rat Brain

Aims: Vasopressin (AVP) and oxytocin (OT) are considered to be related to gastric functions and the regulation of stress response. The present study was to study the role of vasopressinergic and oxytocinergic neurons during the restraint waterimmersion stress. Methods: Ten male Wistar rats were divided into two groups, control and RWIS for 1h. The brain sections were treated with a dual immunohistochemistry of Fos and oxytocin (OT) or vasopressin (AVP) or OT receptor or AVP 1b receptor (V1bR). Results: (1) Fos-immunoreactive (Fos-IR) neurons dramatically increased in the hypothalamic paraventricular nucleus (PVN), the supraoptic nucleus (SON), the neucleus of solitary tract (NTS) and motor nucleus of the vagus (DMV) in the RWIS rats; (2) OT-immunoreactive (OT-IR) neurons were mainly observed in the medial magnocellular part of the PVN and the dorsal portion of the SON, while AVP-immunoreactive (AVP-IR) neurons mainly distributed in the magnocellular part of the PVN and the ventral portion of the SON. In the RWIS rats, Fos-IR neurons were indentified in 31 % of OT-IR neurons and 40 % of AVP-IR neurons in the PVN, while in the SON it represented 28%, 53 % respectively; (3) V 1bR-IR and OTR-IR neurons occupied all portions of the NTS and DMV. In the RWIS rats, more than 10 % of OTR-IR and V1bR-IR neurons were activated in the DMV, while lower ratio in the NTS. Conclusion: RWIS activates both oxytocinergic and vasopressinergic neurons in the PVN and SON, which may project to th

Electrophysiological and morphological heterogeneity of rat dorsal vagal neurones which project to specific areas of the gastrointestinal tract

The electrophysiological properties of rat dorsal motor nucleus of the vagus (DMV) neurones (n = 162) were examined using whole cell patch clamp recordings from brainstem slices. Recordings were made from DMV neurones whose projections to the gastrointestinal tract had been identified by previously applying fluorescent retrograde tracers to the gastric fundus, corpus or antrum/pylorus, or to the duodenum or caecum.The neuronal groups were markedly heterogeneous with respect to several electrophysiological properties. For example, neurones which projected to the fundus had a higher input resistance (400 ± 25 MΩ), a smaller and shorter after-hyperpolarization (16.7 ± 0.49 mV and 63.5 ± 3.9 ms) and a higher frequency of action potential firing (19.3 ± 1.4 action potentials s−1) following injection of depolarizing current (270 pA) when compared with caecum-projecting neurones (302 ± 22 MΩ; 23.5 ± 0.87 mV and 81.1 ± 5.3 ms; 9.7 ± 1.1 action potentials s−1; P < 0.05 for each parameter). Differences between neuronal groups were also apparent with respect to the distribution of several voltage-dependent potassium currents. Inward rectification was present only in caecum-projecting neurones, for example.Neurones (n = 82) were filled with the intracellular stain Neurobiotin allowing post-fixation morphological reconstruction. Neurones projecting to the caecum had the largest cell volume (5238 ± 535 μm3), soma area (489 ± 46 μm2) and soma diameter (24.6 ± 1.24 μm) as well as the largest number of dendritic branch segments (23 ± 2).In summary, these results suggest that DMV neurones are heterogeneous with respect to some electrophysiological as well as some morphological properties and can be divided into subgroups according to their gastrointestinal projections