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PubMed2005

Suppression of stress-induced nNOS expression in the rat hypothalamus by biting.

Nitric oxide (.NO) modulates the activity of the endocrine system in the behavioral response to stress. The purpose of this study was to investigate the effect of restraining the body of an animal on expression of neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) of the hypothalamus, and the inhibitory effect of para-masticatory activity on restraint-induced nNOS expression. We observed an increase in nNOS mRNA expression and nNOS-positive neurons in the rat hypothalamus after 30 or 60 min of restraint. Biting on a wooden stick during bodily restraint decreased nNOS mRNA expression in the hypothalamus. In addition, the number of nNOS-positive neurons was significantly reduced in the PVN of the hypothalamus. These observations clearly suggest a possible anti-stress effect of the masticatory activity of biting, and this mechanism might be unconsciously in operation during exposure to psychological stressors.

Adaptation, Psychological↗

PubMed1993

Bacterial lipopolysaccharide-induced expression of interleukin-6 messenger ribonucleic acid in the rat hypothalamus, pituitary, adrenal gland, and spleen.

Whereas the stimulatory effect of interleukin-6 (IL-6) on the hypothalamic-pituitary-adrenal (HPA) axis is well established, its mode of action in this axis has yet to be fully elucidated. To further study the role of IL-6 in the HPA axis, we compared the expression of IL-6 messenger RNA (mRNA) in the rat hypothalamus, pituitary, and adrenal gland with that in the spleen after ip or intracerebroventricular (icv) administration of bacterial lipopolysaccharide (LPS). After either ip or icv administration, LPS induced the expression of IL-6 mRNA, which consists of 1.2 kilobases (kb) and 2.4 kb subclasses, in all these tissues of the HPA axis as well as in the spleen. Although we used 100 times less amount of LPS for the icv administration than that used for ip LPS, plasma ACTH levels in both the conditions rapidly reached comparable levels. This icv dose induced IL-6 mRNA expression in the hypothalamus faster than ip dose but also stimulated IL-6 mRNA expression in the hypothalamus, pituitary, and adrenal gland more effectively and smoothly than the ip LPS dose did. Northern blot analysis revealed that in the hypothalamus, pituitary, and adrenals, the predominant subclass of IL-6 mRNA was not 1.2 kb but 2.4 kb. In contrast, this subclass was the minor component in the spleen induced under the same circumstances. These findings indicate that IL-6-synthesizing cells in the HPA axis differ in character from those in the spleen, and that LPS applied in vivo may modulate IL-6 expression in these cells directly and/or indirectly through secondarily activated functions in the neuronal or endocrine systems.

Animals↗

PubMed2002

Administration of Folium mori extract decreases nitric oxide synthase expression in the hypothalamus of streptozotocin-induced diabetic rats.

Folium mori, the leaves of Morus alba L., has traditionally been used for the treatment of diabetic hyperglycemia. It has been shown to induce enhanced NOS expression in the hypothalamus of rats with streptozotocin (STZ)-induced diabetes. In the present study, the effect of Folium mori on the expression of nitric oxide synthase (NOS) in the hypothalamus of STZ-induced diabetic rats was investigated via nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry. Enhanced NAPDH-d expression was detected in the paraventricular nucleus, ventromedial hypothalamic nucleus, and lateral hypothalamic area of the hypothalamus in the STZ-induced diabetes group. Administration of the aqueous extract of Folium mori to rats with STZ-induced diabetes resulted in decreased NADPH-d positivity. These results suggest that Folium mori treatment is effective in curbing the desire for food under diabetic conditions via modulation of NO expression in the hypothalamus.

Animals↗

PubMed2004

Suprachiasmatic nuclei grafts restore the circadian rhythm in the paraventricular nucleus of the hypothalamus.

The mammalian suprachiasmatic nucleus (SCN) controls the circadian rhythm of many physiological and behavioral events by an orchestrated output of the electrical activity of SCN neurons. We examined the propagation of output signals from the SCN into the hypothalamus, especially into the region of the paraventricular nucleus, through multimicroelectrode recordings using acute and organotypic brain slices. Circadian rhythms in spontaneous firing rate with a period close to 24 hr were demonstrated in the SCN, in directly adjacent hypothalamic regions, and in the region of the paraventricular nucleus of the hypothalamus, an important center for the integration of neuroendocrine, homeostatic, and autonomic functions. The activity rhythms recorded from structures outside of the SCN were in phase with the rhythms in the SCN. Cyclic information in the hypothalamus was lost after ablation of the SCN but could be restored by SCN grafts, indicating that a humoral factor is responsible for the restoration of circadian rhythmicity in the absence of neural connections. Periodic application of arginine-vasopressin (AVP) provided evidence that AVP can induce rhythmicity in the hypothalamus. These data indicate that the SCN uses a dual (neuronal and humoral) mechanism for communication with its targets in the brain.

Animals↗

PubMed1991

Effect of insulin-like growth factor I on gonadotropin release from the hypothalamus-pituitary axis in vitro.

The effects of insulin-like growth factor-I on gonadotropin release were studied using primary culture of rat anterior pituitary cells incubated with IGF-I (20-5000 micrograms/l) and a hypothalamus-pituitary perifusion system, in which either the mediobasal hypothalamus-pituitary unit or the pituitary were perifused with IGF-I (20-2000 micrograms/l). In primary cultures of rat anterior pituitary cells, IGF-I (2000 micrograms/l) caused a significant increase in the release of both LH (46% increase) and FSH (27% increase). It also caused a significant decrease in the cellular content of LH (9%) and FSH (19%). Its effects in stimulating gonadotropin release were suppressed by administration of anti IGF-I receptor antibody (1 mg/l). In the perifusion system, IGF-I (2000 micrograms/l) did not affect the LH release from the hypothalamus-pituitary or pituitary alone. However, it caused a significant increase in the GnRH (10(-9) mol/l) stimulated LH release from perifused pituitary. These data suggest that IGF-I enhances pituitary gonadotropin release via the IGF-I receptor, but its effect on the hypothalamus was not confirmed.

Animals↗

PubMed1976

The vasopressin and oxytocin content in the hypothalamus and neurohypophysis as influenced by reserpine treatment during long-term dehydration in the white rat.

In dehydrated rats both neurohypophysial hormones diminished in hypothalamus as well as in the neurohypophysis. Oxytocin disappearef from the hypothalamus and neurohypophysis at a more rapid rate than vasopressin did. The minimal content of vasopressin and oxytocin in the hypothalamus was observed during 3rd--4th day, but even in extreme dehydration it was found to be relatively high: 65 per cent of vasopressin and 27 per cent of oxytocin as compared with intact animals. At that time the neurohypophysial vasopressin and oxytocin content were almost fully exhausted. In dehydrated and additionally reserpinized animals (10 mg/kg intraperitoneally, then each 48 hr 5 mg/kg of initial body weight) the vasopressin and and oxytocin hypothalamus and neurohypophysis changed in a similar manner. In some experimental groups the decrease of neurohormones in both sites was more marked under reserpine treatment. The drug seems therefore rather to potentiate the effects of physiological stimulation of osmodetectors. So the existence of monoaminergic stimulatory synapses, directly involved in the neural pathway between the osmodetector and the neurosecretory cell, appears to be hardly probable.

Animals↗

PubMed2005

Caloric restriction reduces cell loss and maintains estrogen receptor-alpha immunoreactivity in the pre-optic hypothalamus of female B6D2F1 mice.

Life-long calorie restriction (CR) remains the most robust and reliable means of extending life span in mammals. Among the several theories to explain CR actions, one variant of the neuroendocrine theories of aging postulates that changing hypothalamic sensitivity to endocrine feedback is the clock that times phenotypic change over the life span. If the feedback sensitivity hypothesis is correct, CR animals should display a significantly different pattern of hormone-sensitive cell density and distribution in the hypothalamus. Of the many endocrine signal receptors that may be involved in maintaining hypothalamic feedback sensitivity, our study has selected to begin mapping those for estrogen (E). Altered hypothalamic sensitivity to E is known to schedule reproductive maturation and influence reproductive senescence. Taking estrogen receptor-alpha (ERalpha) immunoreactivity as an index of sensitivity to E, we counted ERalpha immunoreactive and non-immunoreactive cells in the pre-optic hypothalamus of young (6 weeks), ad-libitum (Old-AL) fed old (22 months), and calorie restricted (Old-CR) old (22 months) female B6D2F1 mice. An automated imaging microscopy system (AIMS) was used to generate cell counts for each sampled section of pre-optic hypothalamus. Results show a 38% reduction in ERalpha immunoreactive cells and an 18% reduction in total cell numbers in AL-old mice in comparison to young mice. However, CR mice only show a 19% reduction in ERalpha immunoreactive cells and a 13% reduction in total cell numbers in comparison to young mice. This indicates CR prevents age-related cell loss and maintains estrogen sensitivity in the pre-optic hypothalamus of old female B6D2F1 mice.

Aging↗

PubMed1990

[Effect of acupuncture and moxibustion on hypothalamus-pituitary-adrenal axis suffering from simple obesity].

In order to understand the effect of acupuncture and moxibustion on hypothalamus-pituitary-adrenal axis in simple obesity, the authors have observed the obese indices, the lipid level, the content of ACTH in plasma and that of salivary cortisol in 39 simple obesity before and after the acupuncture and moxibustion treatment. The results showed that the markedly effective rate was 38.5%, the effective rate was 51.3%, the ineffective rate was 10.3% and the total effective rate was 89.7% after treatment. The results also showed that the function of hypothalamus-pituitary-adrenal axis in simple obesity was lower than that of normal. Acupuncture and moxibustion treatment not only regulated the lipid level and achieved the antiobesity effect but also enhanced the function of hypothalamus-pituitary-adrenal system. The results suggested that the key factor of antiobesity by acupuncture and moxibustion was to increase the function of hypothalamus-pituitary-adrenal system.

Acupuncture Therapy↗

PubMed1979

An autoradiographic study of the efferent connections of the ventromedial nucleus of the hypothalamus.

Efferent projections from the ventromedial nucleus of the hypothalamus (VMN) were traced using tritiated amino acid autoradiography in albino rats. Ascending fibers passed through the anterior hypothalamus. Labelled fibers and terminal fields were seen in the preoptic area, bed nucleus of the stria terminalis, substantia innominata, the anterior amygdaloid area, diagonal bands of Broca and lateral septum. Fibers also projected laterally from VMN and entered the supraoptic commissures and zona incerta. These lateral projections were responsible for the fibers observed in the cerebral peduncle, the amygdala, the thalamus and the reticular formation. Fibers descending in a medial position projected through the posterior hypothalamus and then swept dorsally to terminate in the mesencephalic and pontine central grey. A projection from VMN into the median eminence was noted. The overall patterns of projection from different parts of VMN were similar; differences that existed were primarily in the relative strengths of the different projections. The efferent projections from VMN are extensive, well organized, and would appear capable of supporting significant physiological actions on extra-hypothalamic structures.

Amygdala↗

PubMed1981

Efferent projections of the medial preoptic nucleus and medial hypothalamus in the pigeon.

The efferent projections of the medial preoptic nucleus (POM), anterior-medial hypothalamic area (AM), and the posteromedial hypothalamic nucleus (PMH) in the pigeon were traced by the autoradiographic technique. Similar and differential connections were noted from these regions. Projections from POM and AM-PMH were traced to nucleus septalis lateralis, nucleus dorsomedialis thalami, nucleus dorsolateralis anterior thalami (pars ventralis), posterior hypothalamic and medial mammillary areas, area ventralis tegmenti (Tsai), central gray of midbrain and nucleus intercollicularis and substantia grisea periventricularis of the midbrain. The density of silver grains in these regions differed with POM and AM-PMH injections. Other projections were observed exclusively from only one or two of the nuclear regions injected. Connections from POM and the rostral part of AM were seen to the median eminence, neurohypophysis, and the nucleus of anterior pallial commissure. Only cells of the anterior part of AM project fibers to nucleus septalis medialis. In the hypothalamus, projections from POM are concentrated in the periventricular region and in the preoptic-hypophyseal tract in the extreme lateral hypothalamus, while AM-PMH projections are heaviest in the medial hypothalamus and lateral preoptic area. A major difference in the connections of PMH from POM is the more substantial PMH projection to the midbrain. A prominent projection courses dorsolaterally and posteriorly from PMH toward nucleus ovoidalis and splits into two pathways: a lateral pathway which heavily innervates n. intercollicularis and the periventricular gray and a ventrolateral projection to the midbrain tegmentum. The projections described above provide anatomical substrates for neuroendocrine, autonomic, and behavioral functions.

Animals↗

PubMed1984

Distribution of tyrosine-hydroxylase-immunoreactive neurons in the hypothalamus of rats.

The distribution and morphology of cells containing tyrosine hydroxylase (TH) immunoreactivity in the hypothalamus of rats were studied by using a modified immunoperoxidase technique. The TH cell system is more complexly organized than was previously thought. On the basis of their clustering patterns, hypothalamic TH neurons could be subdivided into two groups: dorsal and ventral. The ventral group consists of a prominent aggregate of cells located in the caudal part of the arcuate nucleus. From here, cells extend around the caudal part of the ventromedial and dorsomedial nuclei and the base of the diencephalon. Tyrosine hydroxylase-positive cells are present throughout the arcuate nucleus, except in its ventromedial part. Anteriorly, immunoreactive cells appear in the suprachiasmatic and supraoptic nuclei, in the retrochiasmatic area, and in the ventral part of the anterior hypothalamic nucleus. The dorsal group has its main concentration of cells in the medial part of the zona incerta, from which two clusters of cells, one medial and one lateral, extend rostralward. The medial group comprises cells in the medial part of the dorsomedial, paraventricular, and anterior hypothalamic nuclei. These cells adjoin the periventricular cells. The lateral group of cells emanating from the zona incerta occupies the lateral part of the dorsomedial and anterior hypothalamic nuclei and the dorsal hypothalamic area. The dorsal and ventral TH cell groups are in continuity medially in the periventricular layer, and laterally through the cells that surround the ventromedial nucleus. Although the cells vary widely in size, shape, and dendritic arborization pattern, there are two main cell types. Small (21 X 11 microns), round to fusiform cells, with two or three dendrites arborizing simply, were frequently seen in the arcuate, suprachiasmatic, periventricular, supramammillary nuclei and at the borders of the ventromedial nucleus. The other cell type is larger (40 X 15 microns) and multipolar, with three to five frequently branching dendrites. The dendritic field is large and the cells are intensely TH-immunoreactive. Although the larger cells occur occasionally in every hypothalamic nucleus, their principal locations are in the dorsal parts of the dorsomedial, posterior hypothalamic nuclei and the dorsal and lateral parts of the zona incerta, and in the areas dorsal and medial to the mammillothalamic tract at caudal hypothalamic levels. In this paper we give a detailed description of TH-immunoreactive fibers and terminals in the hypothalamus and a comparison with previous studies of catecholamine cells in the hypothalamus.

Animals↗

PubMed1978

Afferent fiber connections from lower brain stem to hypothalamus studied by the horseradish peroxidase method with special reference to noradrenaline innervation.

Attempts were made to determine the afferent projections to the anterior hypothalamus including the preoptic area from the lower brain stem by means of the horseradish peroxidase method combined with monoamine oxidase staining to identify noradrenaline (NA) neurons. In addition to this technique, a histofluorescence analysis was performed. NA fibers in the medial part of the anterior hypothalamus were mainly supplied by A1 and A2 NA neuron groups, while the lateral part and periventricular zone received NA terminals from both pontine and medulla oblongata NA neuron groups. Furthermore, the present study indicated that there were direct projections to the anterior hypothalamus from non-noradrenergic neurons in the lower brain stem: nuclei raphe dorsalis, centralis superior, cells in the mesencephalic and pontine central gray matter, nuclei parabrachialis lateralis and medialis, cells around fasciculus longitudinalis medialis.

Afferent Pathways↗

PubMed1980

Substance P-related peptides in the hypothalamus of amphibia.

The occurrence of Substance P-(SP)-related peptides in the hypothalamus of three species of Amphibia (newt, clawed, toad, frog) was studied immunohistochemically employing the direct immunofluorescence method or a double-step technique (indirect immunofluorescence followed by the peroxidase-antiperoxidase complex method). SP-like immunopositive fibers are seen throughout the hypothalamus. They are especially abundant in the preoptic area and in the outer zone of the median eminence, suggesting a role of SP-related peptides in the hypothalamo-hypophysial regulation in these animals. Some SP-like neurons are seen in the posterior hypothalamus and in the preoptic area. In the newt, such SP-like immunopositive neurons occur frequently in the preoptic periventricular grey.

Animals↗

PubMed1975

Autoradiographic localization of 3H-gamma-aminobutyric acid in the medial hypothalamus.

Tritium labelled gamma-aminobutyric acid (3H-GABA) was infused into the third ventricle of rats with normal or deafferented hypothalamus and the distribution of the label was studied by light and electron microscopic autoradiography. In control as well as deafferented hypothalamus a few neurones accumulated radioactivity, while the majority was unlabelled. Characteristic clusters and rows of silver grains were observed in the neuropil of several regions probably indicating labelled cell processes and terminal axons. Electron microscopy showed that at least some of the clusters were over axon terminals with synaptic vesicles. 3H-GABA accumulated also in the ependyma and glial elements. The results suggest that in the medial hypothalamus there is a preferential uptake of GABA in some neurones and nerve fibers; at least some of these are hypothalamic interneurones. This supports the hypothesis that some hypothalamic neurones and nerve endings may use GABA as a transmitter.

Alanine↗

PubMed1980

Rise in blood pressure increases the release of endogenous catecholamines in the anterior hypothalamus of the cat.

In anaesthetized cats, anterior and posterior hypothalamic areas were simultaneously superfused with artificial CSF using two push-pull cannulae. The rates of release of endogenous catecholamines were determined in the superfusates which were continuously collected in periods of 10 seconds. In both areas, the rate of release of dopamine was higher than the rates of release of noradrenaline and adrenaline. Electrical stimulation of the splanchnic nerve elicited a rise in the arterial blood pressure and increased the rates of release of noradrenaline, adrenaline and dopamine in the anterior hypothalamic area. The rates of release of the catecholamines in the posterior hypothalamic area were not influenced by the pressor response to stimulation of the splanchnic nerve. Transection of the brain caudal to the hypothalamus reduced the rates of release of the catecholamines in the anterior hypothalamus and abolished the releasing effect of the stimulation of the splanchnic nerve. The results indicate that acute rise in blood pressure activates catecholamine cell bodies in the lower brain stem, which in turn stimulate the anterior hypothalamus to counteract the pressor response.

Animals↗

PubMed1998

Oxytocin immunoreactivity in the hypothalamus of female hamsters.

In Syrian hamsters (Mesocricetus auratus), oxytocin (OXT) activity within the medial preoptic-anterior hypothalamus (MPOA-AH) and the ventromedial hypothalamus (VMH) plays an important role in the expression of sexual receptivity. Immunocytochemical analysis with OXT-specific antibodies was used to identify the distribution of OXT-containing cell bodies and fibers in female hamster brain and to determine the possible sources of OXT important for sexual receptivity. Oxytocin-immunoreactive cell bodies and fibers were found in several regions of the preoptic area, including the medial preoptic area, the medial preoptic nucleus, and the bed nucleus of the stria terminalis. Large numbers of cell bodies and fibers were localized within the paraventricular and supraoptic nuclei, and in anterior hypothalamus. OXT-immunoreactive fibers were observed in the VMH and the ventral tegmental area. The anatomical data from the present study support the hypothesis that OXT activity in the MPOA-AH and the VMH plays an important role in the regulation of sexual receptivity in hamsters.

Animals↗

PubMed1984

Lateralization of LH-RH in rat hypothalamus.

An asymmetrical LH-RH distribution in rat hypothalamus has been found. In Wistar rats LH-RH content in the right hypothalamus exceeds that in the left one; in albino rats a contrary distribution is observed. LH-RH lateralization changes during a 24-h period. Unilateral castration or cold stress lead to a shift in LH-RH distribution in the hypothalamus.

Animals↗

PubMed1991

Immunocytochemical evidence for noradrenergic regulation of estrogen receptor concentrations in the guinea pig hypothalamus.

The noradrenergic system interacts with steroid hormones to influence female sexual behavior and gonadotropin release in rodents. Using a double label immunocytochemical procedure for estrogen receptors and dopamine-beta-hydroxylase, we investigated the anatomical relationships between noradrenergic neurons and estrogen receptor-immunoreactive (ER-IR) cells in the brain of ovariectomized female guinea pigs. Dopamine-beta-hydroxylase-immunoreactive (DBH-IR) varicosities were closely associated with ER-IR cells throughout the hypothalamus and preoptic area. This anatomical relationship was observed with almost 80% of the ER-IR cells in the ventrolateral hypothalamus (VLH), an area involved in the regulation of female sexual behavior in guinea pigs. Furthermore, the presence of closely associated DBH-IR varicosities was related to staining intensity of ER-IR neurons. In the rostral VLH, ER-IR neurons with closely associated DBH-IR varicosities stained more darkly than ER-IR neurons lacking this association, suggesting noradrenergic regulation of basal levels of cellular estrogen receptors. These findings provide neuroanatomical evidence suggestive of noradrenergic regulation of estrogen receptor levels in the hypothalamus of female guinea pigs.

Animals↗