Involvement of NMDA receptor mechanisms in the modulation of serotonin release in the lateral parabrachial nucleus in the rat.

Microdialysis was employed to investigate whether N-methyl-d-asparatate (NMDA) glutamate receptor mechanisms are involved in the modulation of serotonin (5-hydoxytryptamine, 5-HT) release in the region of the lateral parabrachial nucleus (LPBN) in freely moving rats. Perfusion of NMDA (10 and 50 microM) through the microdialysis probe significantly enhanced extracellular concentrations of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the LPBN area. Local perfusion of the NMDA antagonist dizocilpine (MK801, 10 and 50 microM) did not change the basal 5-HT and 5-HIAA levels in the LPBN area.

Involvement of serotonergic systems in the lateral parabrachial nucleus in sodium and water intake: a microdialysis study in the rat.

The present study was carried out to investigate whether 0.3 M NaCl and water intake alters the release of serotonin (5-hydoxytryptamine, 5-HT) in the region of the lateral parabrachial nucleus (LPBN) in freely moving rats. The ingestion of 0.

Drinking decreases the noradrenaline release in the median preoptic area caused by hypovolemia in the rat.

Previous observations have suggested that the noradrenergic system in the median preoptic nucleus (MnPO) is implicated in the regulation of body fluid balance and cardiovascular function. The present study was carried out to investigate whether water intake alters the release of noradrenaline (NA) in the MnPO area caused by hypovolemia in freely moving rats. Nonhypotensive hypovolemia was induced by subcutaneous polyethylene glycol (PEG), and extracellular levels of NA were measured using intracerebral microdialysis techniques.

Noradrenaline release in the median preoptic nucleus area caused by hemorrhage in the rat.

The present study was designed to examine whether noradrenergic projections from the A1 cell group in the ventrolateral medulla to the median preoptic nucleus (MnPO) transmit information from the peripheral baroreceptors. In urethane-anesthetized male rats, extracellular concentrations of noradrenaline (NA) in the region of the MnPO in response to hemorrhage (5 or 10 ml/kg) were monitored with in vivo microdialysis methods. Hemorrhage significantly increased the NA release in the MnPO area.

GABAergic modulation of noradrenaline release in the median preoptic nucleus area in the rat.

Microdialysis was employed to investigate whether gamma-aminobutyric acid (GABA) receptor mechanisms are involved in the regulation of noradrenaline (NA) release in the median preoptic nucleus (MnPO) in awake, freely moving rats. Perfusion with the GABA receptor antagonists as well as agonists was performed in the region of the MnPO through a microdialysis probe and dialysate levels of NA were measured. Perfusion with either bicuculline (10 and 50 microM), a GABA(A) receptor antagonist, or phaclofen (10 and 50 microM), a GABA(B) receptor antagonist, enhanced the release of NA in the MnPO area.

Reduced dipsogenic response induced by angiotensin II activation of subfornical organ projections to the median preoptic nucleus in estrogen-treated rats.

The present study was carried out to investigate whether estrogen modulates the drinking response induced by activation of angiotensinergic neural pathways from the subfornical organ (SFO) to the median preoptic nucleus (MnPO). Microinjection of angiotensin II (ANG II, 10(-10) M, 0.2 microl) into the SFO elicited drinking in ovariectomized (OVX) female rats that were treated with either propylene glycol (PG) vehicle or estrogen benzoate (EB).

Decreased monoamine release in the median preoptic area following ventricular treatment with the angiotensin II antagonist saralasin in normotensive and spontaneously hypertensive rats.

Previous findings have shown that some of the neurons in the median preoptic nucleus (MnPO) receive both catecholaminergic inputs from the brainstem and angiotensinergic inputs from the subfornical organ (SFO), and that alterations in the function of the brain renin-ANG system are implicated in hypertension, especially in spontaneous hypertensive rats (SHR). In an attempt to clarify the action of these inputs on MnPO neurons and to find the difference in the action between normotensive Wistar-Kyoto (WKY) rats and SHR, we used microdialysis to investigate the effects of injections of saralasin (Sar), an angiotensin II (ANG II) antagonist, into the third ventricle (3V) on monoamine release in the MnPO area of awake WKY and SHR. The content of noradrenaline (NA) in the MnPO area was significantly higher in SHR.

Attenuated drinking response induced by angiotensinergic activation of subfornical organ projections to the paraventricular nucleus in estrogen-treated rats.

The present study was carried out to examine whether estrogen modulates the drinking response caused by activation of neural pathways from the subfornical organ (SFO) to the hypothalamic paraventricular nucleus (PVN) in the female rat. Microinjection of angiotensin II (ANG II) into the SFO elicited drinking in ovariectomized female rats that were treated with either propylene glycol (PG) vehicle or estradiol benzoate (EB). The amount of water intake induced by the ANG II injection was significantly greater in the PG-treated than in the EB-treated animals.

Enhanced response of subfornical organ neurons projecting to the hypothalamic paraventricular nucleus to angiotensin II in spontaneously hypertensive rats.

Thirty subfornical organ (SFO) neurons in normotensive Wistar-Kyoto (WKY) rats and 32 SFO neurons in spontaneously hypertensive rats (SHR) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) under urethane anesthesia. The spontaneous firing rate was significantly higher in SHR than in WKY rats. No significant differences in the latency, conduction velocity, and threshold of antidromic response were observed between WKY and SHR.