No abstract

Corticotropin releasing hormone (CRH), a major regulator of pituitary ACTH secretion, also acts as a neurotransmitter in the brain. To determine whether CRH is involved in the regulation of hypothalamic function during stress, CRH receptor binding and CRH receptor mRNA levels were studied in the hypothalamus of rats subjected to different stress paradigms: immobilization, a physical-psychological model; water deprivation and 2% saline intake, osmotic models; and i.p. hypertonic saline injection, a combined physical-psychological and osmotic model. In agreement with the distribution of CRH receptor binding in the brain, in situ hybridization studies using 35S-labeled cRNA probes revealed low levels of CRH receptor mRNA in the anterior hypothalamic area, which were unaffected after acute or chronic exposure to any of the stress paradigms used. Under basal conditions, there was no CRH binding or CRH receptor mRNA in the supraoptic (SON) or paraventricular (PVN) nuclei. However, 2 h after the initiation of acute immobilization, CRH receptor mRNA hybridization became evident in the parvicellular division of the PVN, with levels substantially increasing from 2 to 4 h, decreasing at 8 h and disappearing by 24 h. Identical hybridization patterns of CRH receptor mRNA were found in the parvicellular PVN after repeated immobilization; levels were similar to those after 2 h single stress following immobilization at 8-hourly intervals for 24 h (3 times), and very low, but clearly detectable 24 h after 8 or 14 days daily immobilization for 2 h. On the other hand, water deprivation for 24 or 60 h and intake of 2% NaCl for 12 days induced expression of CRH receptor mRNA in the SON and magnocellular PVN, but not in the parvicellular pars of the PVN.(ABSTRACT TRUNCATED AT 250 WORDS)

Double staining in situ hybridization studies have shown that angiotensin II (AII) type 1 receptors (AT1) in the hypothalamic paraventricular nucleus (PVN) are located primarily in corticotropin releasing hormone (CRH) neurons of the parvicellular subdivision. The purpose of these studies was to investigate the role of AII regulating the hypothalamic-pituitary adrenal (HPA) axis, by correlating AT1 receptor expression levels in the PVN with the known changes in activity of the HPA axis under different stress paradigms, and manipulation of circulating glucocorticoids. AT1 receptor mRNA was measured by in situ hybridization using 35S-labelled cRNA probes and AII binding by autoradiography using 125I[Sar1,Ile8]AII in slide mounted hypothalamic sections. AT1 receptor mRNA levels and AII binding in the PVN were reduced by about 20% 18 h after adrenalectomy remaining at these levels up to 6 days after. This effect was prevented by corticosterone administration in the drinking water, or dexamethasone injection (100 mg, s.c., daily). Conversely, dexamethasone injection in intact rats caused a 20% increase in AT1 receptor mRNA in the PVN. AT1 receptor mRNA and binding in the PVN increased 4 h after exposure to stress paradigms associated with activation of the HPA axis (immobilization for 1 h, or i.p. injection of 1.5 M NaCl), and remained elevated after repeated daily stress for 14 days. Unexpectedly, two osmotic stress models associated with inhibition of the HPA axis (60 h water deprivation or 12 days of 2% saline intake) also resulted in increased AT1 receptor mRNA levels and AII binding in the parvicellular PVN. In intact rats, the stimulatory effect of acute stress on AT1 receptor mRNA in the PVN was significantly enhanced by dexamethasone administration (100 micrograms, s.c., 14 h and 1 h prior to stress), while in adrenalectomized rats, with or without glucocorticoid replacement, stress reduced rather than increased, AT1 receptor mRNA. Dexamethasone, 100 micrograms, injected sc within 1 min the beginning of immobilization in adrenalectomized rats, increased AT1 receptor mRNA in the PVN to levels significantly higher than those after dexamethasone alone, indicating that the stress induced glucocorticoid surge is required for the stimulatory effect of stress on AT1 receptor mRNA. The data suggest that AT1 receptor expression in the PVN is under dual control during stress: stress-activated inhibitory pathways and the stimulatory effect of glucocorticoids. The lack of specificity of the changes in AT1 receptor expression in the PVN following stressors with opposite effects on ACTH secretion (osmotic and physical-psychological stress) does not support a role for AII as a major determinant of the response of the HPA axis during stress.

The structures of the antimalarials dihydroqinghaosu (2), artemether (3), and artesunic acid (7a) derived from qinghaosu were elaborated by 1H‐NMR spectroscopy, and supported with X‐ray data obtained for 2 and 3. Several new derivatives, useful for the chemical characterization of dihydroqinghaosu (2) and artesunic acid (7a), were prepared.