Inhibitory response in neurosecretory cells of the hypothalamic supraoptic nucleus to subiculum stimulation in lactating rats

The effects of subiculum stimulation were investigated in 80 antidromically identified hypothalamic supraoptic neurons in lactating rats. Inhibition manifesting as suppression of antidromic action potentials (or of their somatodendritic component) was revealed in 26% of cells, induced by applying conditioned and test stimuli to the subiculum and neurohypophysial stalk. In some instances inhibition arose following a latency of 5–25 msec after each subicular stimulus and lasted only briefly; it set in gradually in other cases, leading to stable long-term changes in the excitability of neurosecretory cells. No activation was produced by this stimulation. It is deduced that subicular inhibitory inputs follow different patterns, thus reflecting morphological organizational aspects of synaptic inhibitory inputs to neurosecretory cells.A. A. Ukhtomskii, Institute of Physiology, A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 4, pp. 431–437, July–August, 1988.     

Daily fluctuations of nucleoli in neurosecretory cells of the rat supraoptic nucleus

Summary Daily fluctuations of nucleoli and nucleolar fibrillar centres in neurosecretory cells from the supraoptic nucleus (SON) were investigated in rats artificially synchronized for 3 weeks to a set 12 h light/12 h dark cycle with free access to food and water. Groups of 3 animals were sacrificed by intracardiac perfusion every 4 h for a 24-h period and every 2 h between 22.00 h and 07.00 h. The SON of each animal was removed, and the mean nucleolar volume and the mean volume of the nucleolar fibrillar centres were estimated by a stereological analysis. The quantitative data showed that the fluctuations in the nucleolar volume of SON neurons depend on the time of sacrifice. A peak value was found in animals sacrificed at 03.00 h which was 1.5 times the value found in animals sacrificed at 19.00 h. The volume of fibrillar centres underwent small, but not significant changes over the 24-h period. None of the large fibrillary centres that can be observed in the superior cervical ganglion were found in the SON. Our results demonstrate that in these neurons the size of the nucleolus undergoes daily fluctuations. These results are discussed in the light of previous studies conducted at our laboratory on the circadian rhythm of nucleolar volume and of nucleolar components in neurons of the superior cervical ganglion.     

Modifications of neuronal activity in the rat hypothalamic supraoptic nucleus after long-lasting vibrational stimulation

We analyzed the background impulse activity (BIA) generated by neurons of the rat hypothalamic supraoptic nucleus in the norm and under conditions of long-lasting vibrational stimulation (exposure 5, 10, or 15 days). Distributions of neurons by the level of regularity, dynamics of discharge trains, form of histograms of interspike intervals (ISIs), as well as distributions of neurons by the BIA frequency ranges, were studied. We also calculated the mean frequency of impulsation of the neurons under study and the coefficient of variation of ISIs. After vibrational influences, we found modifications of both the internal structure of the recorded spike trains and the mean frequency of impulsation within the entire studied group and different frequency subgroups. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 224–230, May–June, 2006.     

Ultrastructure of neurosecretory cells of the hypothalamic supraoptic nucleus in white rats following painful stress and during aging

The ultrastructural organization of neurosecretory cells (NSC) belonging to the hypothalamic supraoptic nucleus was investigated in young rats following periods of painful stress differing in duration (of 2 and 20 min). Intact young rats of similar age and others at late stages of development (24–27 months old) served as controls. Short- and longer-acting painful stress was found to intensify and inhibit the functional activity of NSC respectively. Complex ultrastructural changes in the NSC of young rats following protracted painful stress is compared with the ultrastructural organizational pattern in several NSC of aging rats. Findings would imply that aging occurs in rats following prolonged painful stress, resulting from functional hypersecretion and depletion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 389–395, May–June, 1989.     

Investigating the role of the hypothalamic supraoptic nucleus in nociception in the rat

We investigated the role of the hypothalamic supraoptic nucleus (SON) in nociception in the rat. Electrical stimulation of the SON or microinjection of a small dose of L-glutamate sodium into the SON elevated the nociceptive threshold in a dose-dependent manner, while cauterization of the SON decreased the nociceptive threshold. Pituitary removal did not influence the antinociceptive effect of L-glutamate sodium in the SON. The data suggested that the neurons and not the nervous fibers in the SON played an important role in antinociception.     

Background activity of neurons of the supraoptic hypothalamic nucleus in rats under conditions of vibrational stimulation and electromagnetic extrahigh-frequency irradiation

We analyzed background impulse activity of neurons of the supraoptic nucleus of the rat hypothalamus in the course of 15-day-long isolated action of generalized vibrational stimulation and combination of such stimulation with irradiation of the animal’s head with low-intensity extrahigh-frequency (EHF, millimeter-range) electromagmetic waves. The distributions of the neurons by the level of regularity and dynamics of spike trains, separate frequency ranges of impulsation, and pattern of interspike interval (ISI) histograms were estimated. We also calculated the mean frequency of discharges and coefficient of variation of ISIs. A trend toward decreases in the deviations of some parameters of neuronal spike activity generated by supraoptic neurons, which were evident within early time intervals of isolated action of vibration (5 to 10 days), was observed under the influence of EHF electromagnetic irradiation; thus, the latter factor probably exerts a sedative effect. Neirofiziologiya/Neurophysiology, Vol. 39, No. 6, pp. 433–442, November–December, 2007.     

Morphofunctional characteristics of neurosecretory cells of the supraoptic nucleus of rats with parathyroprival hypocalcemia]

Humori-positive neurosecretory cells of the supraoptic nucleus of the hypothalamus have been investigated during various time of parathyroprival hypocalcemia after extirpation of the parathyroid glands. Contents of total and ionized calcium, phosphorus in blood serum have been estimated. Volume of nuclei and nucleoli has been measured. In 5 days functional activity of the supraoptic nucleus increases (lightly stained cells predominate, volume of the nuclei and nucleoli increases). In subsequent 15-30 days its activity decreases (increase in amount of dark-stained cells, nucleolar volume decreases). In 60 days there is a tendency to restoration of neurosecretion.     

Effects of water deprivation and rehydration on c-Fos and FosB staining in the rat supraoptic nucleus and lamina terminalis region

We studied cFos and FosB staining in the supraoptic nucleus (SON) the organum vasculosum of the lamina terminalis (OVLT) and the median preoptic nucleus (MnPO) in adult male rats after water deprivation (24 h, n = 11; 48 h, n = 12) and water deprivation with rehydration (22 h + water, n = 11; 46 h + water, n = 10). Control rats (n = 15) had water available ad libitum. Separate sets of serial sections from each brain were processed for immunocytochemistry using primary antibodies against either c-Fos or FosB protein. Plasma osmolality, vasopressin, hematocrit, and plasma proteins were measured in separate groups (n = 6-7). The number of c-Fos-positive cells in the SON was significantly increased after 24 and 48 h of water deprivation. In contrast, rehydrated groups were not different from control. Water deprivation significantly increased c-Fos staining in both the OVLT and the MnPO, but c-Fos staining was not altered by rehydration. FosB staining in the SON was significantly increased only by 48-h water deprivation, and this effect was significantly decreased by rehydration. In the MnPO and OVLT, FosB staining was significantly increased by water deprivation, and, like c-Fos staining, these increases were not affected by rehydration. Water deprivation significantly increased osmolality and hematocrit, as well as plasma protein and vasopressin concentrations. Plasma measurements from rehydrated rats were not different from control. We conclude that water deprivation and rehydration differentially affect c-Fos and FosB staining in a region-dependent manner.     

Neuropeptidomics of the supraoptic rat nucleus

The mammalian supraoptic nucleus (SON) is a neuroendocrine center in the brain regulating a variety of physiological functions. Within the SON, peptidergic magnocellular neurons that project to the neurohypophysis (posterior pituitary) are involved in controlling osmotic balance, lactation, and parturition, partly through secretion of signaling peptides such as oxytocin and vasopressin into the blood. An improved understanding of SON activity and function requires identification and characterization of the peptides used by the SON. Here, small-volume sample preparation approaches are optimized for neuropeptidomic studies of isolated SON samples ranging from entire nuclei down to single magnocellular neurons. Unlike most previous mammalian peptidome studies, tissues are not immediately heated or microwaved. SON samples are obtained from ex vivo brain slice preparations via tissue punch and the samples processed through sequential steps of peptide extraction. Analyses of the samples via liquid chromatography mass spectrometry and tandem mass spectrometry result in the identification of 85 peptides, including 20 unique peptides from known prohormones. As the sample size is further reduced, the depth of peptide coverage decreases; however, even from individually isolated magnocellular neuroendocrine cells, vasopressin and several other peptides are detected.     

经脂多糖（LPS）处理免疫应答大鼠离体脑片视上核神经元对细胞因？…

实验采用离体脑片全细胞膜片箝记录方法,观察了细胞因子白介素－１β（ＩＬ－１β）和ＩＬ－２对大鼠离体脑片视上核神经元膜电位及自发放电的影响,以期探明免疫应答大鼠视上核神经元对细胞因子敏感性的变化。结果显示,用１００Ｕ／ｍｌ ＩＬ－１β藻流脑片,正常对照的（ｎ＝１５）和脂多糖（ｌｉｐｏｐｏｌｙｓａｃｃｈｙａｒｉｄｅ ＬＰＳ）腹腔注射９ｄ的大鼠视上核神经元（ｎ＝２０）超极化,同时伴有自发放电频率的下降;     

经脂多糖(LPS)处理免疫应答大鼠离体脑片视上核神经元对细胞因子敏感性的变化

实验采用离体脑片全细胞膜片箝记录方法 ,观察了细胞因子白介素 1β(IL 1β)和IL 2对大鼠离体脑片视上核神经元膜电位及自发放电的影响 ,以期探明免疫应答大鼠视上核神经元对细胞因子敏感性的变化。结果显示 ,用 10 0U/mlIL 1β灌流脑片 ,正常对照的 (n =15 )和脂多糖 (lipopolysaccharideLPS)腹腔注射 9d的大鼠视上核神经元 (n =2 0 )超极化 ,同时伴有自发放电频率的下降 ;应用 10 0U/mlIL 2 ,大部分正常对照视上核神经元 (n =14)表现为超极化 ,自发放电减少 ,剩余部分 (n =3)变化不明显 ;在LPS免疫 9d大鼠离体脑片上的 45个视上核神经元中 ,10 0U/ml的IL 2使其中 19个表现为去极化并伴有自发放电频率增加 ,16个变化不明显 ,其余 10个表现为超极化伴放电频率下降。以上结果表明 ,在免疫应答中 ,视上核神经元对细胞因子IL 2的敏感性 ,在一定的程度上发生了改变 ,细胞因子IL 2可能参与了视上核神经元的功能调节 ,进而在免疫应答过程中发挥了调节作用。     

On lipid inclusions in the neurosecretory cells of the supraoptic nucleus of the white mouse subjected to a chronic salt load

Summary The morphology of the neurosecretory cells of the supraoptic nucleus of white mice on the 3rd, 6th, 10th, 14th, 18th and 30th days after loading animals with 5% NaCl was studied with electron, phase contrast, and light microscopy. Lipid droplets were rarely observed in the cytoplasm of intact animals whereas the number of cells containing lipids, as well as the number and the sizes of the inclusions themselves increased during the experiment. The form and the degree of osmiophilia of the lipid inclusions were found to depend on the fixation method. Empty vacuoles were observed in preparations stained with gallocyanin or paraldehyde-fuchsin and counterstained with Heidenhain's azan. These vacuoles correspond to lipid droplets in electron micrographs because of their localization in adjacent sections, the moment of their appearance in the experiment, and the dynamics of their increase. Solubility of these droplets in ortho-xylol is an additional argument for their lipid nature and accounts for the presence of empty vacuoles. Accumulation of lipids in the neurosecretory cells took place against the background of the extremely increased functional activity of these cells due to intensification of the secretory process.     

Direct hypertonic stimulation of the rat supraoptic nucleus increases c-fos expressionin glial cells rather than magnocellular neurones

We investigated whether hypertonicity acts directly on supraoptic neurones to activate c-fos expression. Hypertonic artificial cerebrospinal fluid was infused into the supraoptic nucleus (SON) via a microdialysis probe implanted 24 h previously. The rats were decapitated after 90 min for immunohistochemistry with a Fos protein antibody. Direct hypertonic stimulation increased Fos protein expression in glial cells, identified by glial fibrillary acidic protein immunoreactivity, but not in magnocellular neurones. Similarly, with in situ hybridisation c-fos mRNA expression was predominantly seen in glial cells. Fos expression in SON neurones was stimulated by systemic hypertonicity even with a microdialysis probe in the SON, and magnocellular neurones expressed Fos after direct microinjection of cholecystokinin-8S into the SON. Thus, while direct hypertonic stimulation of SON neurones activates secretion of vasopressin and oxytocin, the c-fos gene is not activated, unlike following systemic hypertonic stimulation. This indicates that excitation of neuronal electrical and secretory activity does not necessarily lead to activation of the c-fos gene. Activation of c-fos expression in glial cells by direct hypertonic stimulation may reflect their role in regulating brain extracellular fluid composition. Received: 11 March 1996 / Accepted: 24 July 1996