Attenuation of stress-induced elevations in plasma ACTH level and body temperature in rats by green odor.

To investigate the effect of green odor on the elevation of the plasma adrenocorticotropic hormone (ACTH) levels and body temperature (T(b)) induced by stress, adult male rats were subjected to a 2-h immobilization stress and exposed to green odor or its vehicle only. In comparison with the vehicle group, animals in the green odor group showed a significant reduction in plasma ACTH levels at the end of the stress when green odor was applied during the stress. The elevated plasma ACTH levels 2 days after the stress were reduced by green odor applied 0, 1, 2, 4 or 6 h after the beginning of the stress. Neither the immediate nor the long-lasting plasma ACTH response was affected by a prestress treatment of green odor. T(b) elevation was evident following the end of the stress and during the light phase the day after the stress. Both the immediate and the long-lasting elevations in T(b) were attenuated by green odor. These data suggest that green odor extracted from green leaves has a relieving effect on plasma ACTH and T(b) levels induced by an immobilization stress for not only immediate but also long-lasting periods.

Maternal behavior: activation of the central oxytocin receptor system in parturient rats?

Parturition plays a critical role in the full expression of maternal behavior in postpartum females, yet the precise mechanism remains unclear. Here we examined the role of parturition in the activation of Fos and FosB in the central oxytocin receptor (OTR) system in rats. Although expression of FosB, not Fos, was seen in the piriform cortex (Pir) and caudate putamen of virgin and pregnant females, activation of Fos and FosB with extensive co-localization was found in the medial preoptic area, the bed nucleus of the stria terminalis and Pir of parturient brain. This parturition induced activation of Fos and FosB was identified in the central OTR-expressing cells as well as in oxytocinergic neurons. Our data provide direct evidence, for the first time, that parturition activates Fos and FosB in the central OTR system. We propose that Fos and FosB may have comparable functions on initiating maternal behavior at parturition.

Brain regions expressing Fos during thermoregulatory behavior in rats.

We surveyed the neural substrata for behavioral thermoregulation with immunohistochemical analysis of the expression of Fos protein in the rat brain. We used an operant system in which a rat exposed to heat (40 degrees C) could get cold air (0 degrees C) for 30 s when it moved into the reward area. Rats moved in and out of the reward area of the system periodically and thus maintained their body temperature at a normal level. In the rats performing heat escape behavior (active group), strong Fos immunoreactivity (Fos-IR) was found in the median preoptic nucleus (MnPO), parastrial nucleus (PS), and dorsomedial hypothalamus (DMH) compared with the controls. Another group of rats (passive group) were given the same temperature changes, regardless of the rat's movement, as those obtained by rats of the active group. Fos-IR in the MnPO was also seen in this group. The present results suggest that the PS and DMH play an important role in the genesis of thermoregulatory behavior, whereas the MnPO may be important for detecting changes in ambient and/or body temperatures.

ATP-induced calcium oscillations and change of P2Y subtypes with culture conditions in HeLa cells.

ATP, UTP, ADP and UDP induced intracellular Ca(2+) responses and oscillations in HeLa cells that sometimes lasted over 1 h. The response is due to the activation of P2Ys, G-protein coupled ATP receptors, because the oscillations persisted for several minutes even in Ca(2+)-free solution, and suramin and PPADS, antagonists of ATP receptors, partially inhibited the response. The potency of these nucleotides varied with the culture or cell conditions, i.e. UTP was generally most potent but in some cases UDP was more potent; responses to UDP were variable while those to ATP were constant. In addition, Ca(2+) responses to ATP and UDP were additive. These findings suggested the existence of two or more subtypes of P2Ys in HeLa cells. RT-PCR experiments revealed the existence of P2Y(2), P2Y(4) and P2Y(6). Recovery from starvation (culture in FBS-free medium overnight and re-addition of FBS) increased the responses to UTP and UDP but not to ATP, suggesting that the number or activity of P2Y(6) and/or P2Y(4) receptors may increase with cell proliferation in HeLa cells.

Chondroitin sulfate proteoglycan phosphacan/RPTPbeta in the hypothalamic magnocellular nuclei.

The hypothalamo-neurohypophysial system synthesizes and releases arginine vasopressin (AVP) and oxytocin (OXT) with physiological stimulation. In the present study, we investigated localization of a chondroitin sulfate proteoglycan (CSPG), phosphacan/RPTPbeta, in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of adult rats at both the light and electron microscopic levels. Immunohistochemical analyses demonstrated stronger phosphacan/RPTPbeta immunoreactivity within the SON and PVN compared with adjacent hypothalamic areas. Double labeling experiments showed phosphacan/RPTPbeta immunoreactivity constituting punctate networks to surround the somata and dendrites of AVP- and OXT-secreting magnocellular neurons. Electron microscopic examination further revealed strong phosphacan/RPTPbeta immunoreactivity at extracellular membrane surface of some axons, somata, and dendrites of the SON, but not of synaptic junctions. Interestingly, phosphacan/RPTPbeta immunoreactivity was also observed at extracellular surface membrane between astrocytic processes and neurons rather than between magnocellular neurons. The present results indicate the high expression of the CSPG, phosphacan/RPTPbeta at the extracellular space in the hypothalamic AVP- and OXT-secreting magnocellular neurons.

Brain oxytocin augments stress-induced long-lasting plasma adrenocorticotropic hormone elevation in rats.

Single stress induces long-lasting changes in the hypothalamo-pituitary--adrenal (HPA) axis of adult animals. Selective oxytocin (OXT) receptor antagonist was administrated into the cerebroventricle of male rats to test its influence on plasma adrenocorticotropic hormone (ACTH) responses induced by immobilization stress. The ACTH level is significantly higher than the control level (P<0.05) up to 6 days after single stress. Although the OXT antagonist did not change the plasma ACTH level at the end of single stress (P=0.59), the antagonist significantly decreased the ACTH concentration at the end of repeated (3 days) stress and 2 days after single stress (P<0.05) compared with controls. The results suggest that endogenous brain OXT enhances the long-lasting but not immediate HPA axis response to stress.