Immunoreactive luteinizing hormone-containing neurons in the brain of the white-footed mouse, Peromyscus leucopus

The distribution of immunoreactive LH in the brain of the white-footed mouse (Peromyscus leucopus) was determined using immunocytochemical procedures. Immunoreactive fibers are located in the hypothalamus, preoptic area, septum and amygdala. Stained cell bodies are seen in the arcuate nucleus and preoptic area. Gonadectomy enhances staining for LH in the brain.     

Primary visual centers in the frog (Rana esculenta L.) and the problem of ipsilateral projections. Radioautographic study]

The topographic organization of the frog's primary visual system has been reexamined in Rana esculenta using autoradiographic technique. 10 to 24 hrs following an intraocular injection of tritiated proline, an intense labelling was observed contralaterally in the various retinal projection centres (preoptic area); neuropils of Bellonci; corpus geniculatum of the thalamus; posterior thalamus; posterodorsal preoptic area; magnocellular pretectal nucleus and basal optic nucleus; tectal laminae A to G of Potter), as already described. Furthermore, the presence of a ipsilateral projection within the hypothalamus (preoptic area), the thalamus (neuropils of Bellonci and corpus geniculatum) and the pretectium (posterior thalami neuropil, pretectal optic area) is confirmed. On the other hand, the existence of ipsilateral retinotectal (to Potter's lamina F) and retino-tegmentomescencephalic projections (to the basal optic nucleus), which were thusfar questioned, has been demonstrated.     

Immunocytochemical localization of GnRH (gonadotropin releasing hormone) systems in the brain of a marine teleost fish,the sole

Summary The GnRH system was studied in the brain of the sole by immunocytochemistry (peroxidase-antiperoxidase method) (PAP) using antibodies to synthetic salmon GnRH (s-GnRH). Two centers containing immunoreactive cell bodies were observed in the forebrain, one located at the junction between the olfactory bulbs and the telencephalon and the other in the preoptic area. Numerous immunoreactive fibers were found, especially in the telencephalon, hypothalamus, pituitary, optic tectum and retina.     

Rate of tryptophan hydroxylation in vivo in brain nuclei of genetically hypertensive rats of the Lyon strain

The rate of tryptophan hydroxylation in vivo is unaltered in brain areas of 5, 9 and 21 week-old Lyon genetically Hypertensive (LH) rats as compared to both Lyon Normotensive (LN) and Low Blood Pressure (LL) rats, except for a decrease in the C1 area of the medulla oblongata in 9 week-old animals.     

The effect of continuously cooling the hypothalamic preoptic area on antibody titre in the rat

Summary Continuous cooling of the hypothalamic preoptic area for 5 days, as well as sublethal infection withSalmonella enteritidis, increased the titre of antibodies against sheep erythrocytes, suggesting that the febrile response stimulates the humoral immune response.We thank Dr W. Mannheim from the Institute of Hygiene for kindly supplying the cultures ofS. enteritidis. This work was supported by the Schwerpunktprogramm Temperaturregulation und-adaptation of the Deutsche Forschungsgemeinschaft.     

Rate of tryptophan hydroxylation in vivo in brain nuclei of genetically hypertensive rats of the Lyon strain

Summary The rate of tryptophan hydroxylation in vivo is unaltered in brain areas of 5, 9 and 21 week-old Lyon genetically Hypertensive (LH) rats as compared to both Lyon Normotensive (LN) and Low Blood Pressure (LL) rats, except for a decrease in the C1 area of the medulla oblongata in 9 week-old animals.Acknowledgment. The authors wish to thank Dr M.F. Belin, Dr J.F. Pujol and Mrs J. Sacquet for their help during this study. This work was supported by the Fondation pour la Recherche Médicale Française and the C.N.R.S.     

Role of the infundibular complex and its neural afferents in the photosexual reflex in the quail]

The photosexual reflex was suppressed in quail after bilateral preoptic lesions. However an anterior-lateral de-afferentation of the hypothalamus of previously preoptic-lesioned quail resulted in partial photo-induced testis growth. As a working hypothesis, it is suggested that the preoptic area may control some unknown extrahypothalamic influences in order to modulate the gonadotropin controlling function of the infundibular area.     

Comparison of the effects of different isomers of bicuculline infused in the preoptic area on male rat sexual behavior

Summary Intracerebral infusion of (+) bicuculline methiodide, but not of its (–) isomer, in the preoptic area, stimulated masculine sexual behavior in rat as evidenced by a decrease in the number of intromissions preceding ejaculation and a shortening of the ejaculation latency and postejaculatory interval. Data suggest a role of the GABAergic system in mediating masculine sexual behavior.Acknowledgments. Authors wish to thank Ms Elisabeth Wallin for excellent technical assistance and Ms Madelene Kröning for preparing the figures.     

Neuroanatomy and neurochemistry of sleep

Sleep is regulated by homeostatic and circadian factors, and the regulation of sleep of mammals shares many molecular properties with the rest state of submammalian species. Several brain structures take part in waking: the basal forebrain, posterior and lateral hypothalamus, and nuclei in the tegmentum and pons. Active sleep mechanisms are located to the preoptic/anterior hypothalamic area. In addition to acetylcholine and monoamines, glutamate and hypocretin/orexin are important waking factors. Gamma-aminobutyric acid and several peptide factors, including cytokines, growth hormone-releasing hormone and prolactin, are related to sleep promotion. Adenosine is an important homeostatic sleep factor acting in basal forebrain and preoptic areas through A1 and A2A receptors. Prolonged waking activates inducible nitric oxide synthase in the basal forebrain, which through energy depletion causes adenosine release and recovery sleep. Numerous genes have been found differentially displayed in waking compared with sleep, and they relate to neural transmission, synaptic plasticity, energy metabolism and stress protection. The genetic background of a few sleep disorders has been solved.     

Alzheimer’s disease: the impact of age-related changes in reproductive hormones

Differences in the prevalence and age of onset of Alzheimer disease (AD) in men and women, and observations that hormone replacement therapy (HRT) may prevent the development of AD, caused many to hypothesize that estrogen deficiency contributes to AD. However, recent trials using estrogen failed to show any benefit in preventing or alleviating the disease. To address this and other inconsistencies in the estrogen hypothesis, we suspect that another hormone of the hypothalamic-pituitary-gonadal axis, luteinizing hormone (LH), as a major factor in AD pathogenesis. Individuals with AD have elevated levels of LH when compared with controls, and both LH and its receptor are present in increased quantities in brain regions susceptible to degeneration in AD. LH is also known to be mitogenic, and could therefore initiate the cell cycle abnormalities known to be present in AD-affected neurons. In cell culture, LH increases amyloidogenic processing of amyloid- protein precursor, and in animal models of AD, pharmacologic suppression of LH and FSH reduces plaque formation. Given the evidence supporting a pathogenic role for LH in AD, a trial of leuprolide acetate, which suppresses LH release, has been initiated in patients.     

Alzheimer’s disease: the impact of age-related changes in reproductive hormones

Receptors for hormones of the hypothalamic-pituitary-gonadal (HPG) axis that regulate reproductive function are expressed throughout the brain, and in particular the limbic system. The most studied of these hormones, the sex steroids, contain receptors throughout the brain, and numerous estrogenic, progestrogenic and androgenic effects have been reported in the brain related to development, maintenance and cognitive functions. Although less studied, receptors for gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and activins also are found throughout the limbic system on a number of cell types, and they too transduce signals from circulating hormones as demonstrated by their multiple effects on the growth, development, maintenance and function of the brain. This review highlights the point that because of the feedback loops within the HPG axis, it is difficult to ascribe structural and functional changes during development, adulthood and senescence to a single HPG hormone, since a change in the concentration of any hormone in the axis will modulate hormone concentrations and/or receptor expression patterns for all other members of the axis. The most studied of these situations is the change in serum and neuronal concentrations of HPG hormones associated with menopause/andropause. Dysregulation of the HPG axis at this time results in increases in the concentrations of serum GnRH, gonadotropins and activins, decreases in the serum concentrations of sex steroid and inhibin, and increases in GnRH and LH receptor expression. Such changes would result in significantly altered neuronal signaling, with the final result being that there is i.e. increased neuronal GnRH, LH and activin signaling, but decreased sex steroid signaling. Therefore, loss of cognitive function during senescence, typically ascribed to sex steroids, may also result from increased signaling via GnRH, LH or activin receptors. Future studies will be required to differentiate which hormones of the HPG axis regulate/maintain cognitive function. This introductory review highlights the importance of the identification of HPG hormone neuronal receptors and the potential of serum HPG hormones to transduce signals to regulate brain structure and function during development and adult life.     

Effects of estradiol-7 alpha-butyric acid on hypothalamus cells]

When Rat uterus was incubated at 37 degrees with estradiol-7 alpha-butyric acid (OII-7 alpha-bu), no interference was observed with the intracellular estradiol receptors. In addition, OII-7 alpha-bu did not display estrogenic effect such as in vivo inhibition of LH secretion in Rat and in vitro increased activity of the enzyme ornithine-decarboxylase in the chick oviduct. Contrary to these negative findings, we have observed preoptic and septal cells in the guinea pig where micro-iontophoresis of OII-7 alpha-bu triggers changes of the electric activity within a second. We submit therefore, that this latter response is due to an interaction between the acid estrogen and the neuron membrane.     

Comparison of the effects of different isomers of bicuculline infused in the preoptic area on male rat sexual behavior

Intracerebral infusion of (+) bicuculline methiodide, but not of its (-) isomer, in the preoptic area, stimulated masculine sexual behavior in rat as evidenced by a decrease in the number of intromissions preceding ejaculation and a shortening of the ejaculation latency and postejaculatory interval. Data suggest a role of the GABAergic system in mediating masculine sexual behavior.     

Proestrous gonadotropin levels in thyroparathyroidectomized female rats

Summary Intact and TPTx animals showed the expected afternoon increase in serum LH, FSH and prolactin levels. But the afternoon increase in serum LH levels in TPTx rats was less than that observed for intact animals (p<0.01). Neither serum prolactin nor FSH levels were altered by TPTx.The excellent technical and secretarial assistance ofS. Hemelt andD. Landman is gratefully acknowledged.     

Functional polymorphisms of the brain serotonin synthesizing enzyme tryptophan hydroxylase-2

Many neuropsychiatric disorders are considered to be related to the dysregulation of brain serotonergic neurotransmission. Tryptophan hydroxylase-2 (TPH2) is the neuronal-specific enzyme that controls brain serotonin synthesis. There is growing genetic evidence for the possible involvement of TPH2 in serotonin-related neuropsychiatric disorders; however, the degree of genetic variation in TPH2 and, in particular, its possible functional consequences remain unknown. In this short review, we will summarize some recent findings with respect to the functional analysis of TPH2. Received 12 September 2005; received after revision 25 October 2005; accepted 31 October 2005     

Physiological arousal: a role for hypothalamic systems

The lateral hypothalamus (LH) has long been known as a homeostasis center of the brain that modulates feeding behavior, arousal and reward. The hypocretins (Hcrts, also called orexins) and melanin-concentrating hormone (MCH) are neuropeptides produced in two intermingled populations of a few thousand neurons in the LH. The Hcrts have a prominent role in regulating the stability of arousal, since Hcrt system deficiency leads to narcolepsy. MCH is an important modulator of energy balance, as MCH system deficiency in mice leads to leanness and increased metabolism. Recently, MCH has been proposed to modulate rapid eye movement sleep in rodents. In this review, we propose a working model of the cross-talk between Hcrt and MCH circuits that may provide an arousal balance system to regulate complex goal-oriented behaviors.     

Isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus Rana): changes during oocyte maturation

Rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly and disassembly dynamics of frog oocyte tubulin compared to that in brain. By using centrifugation, SDS-PAGE, two-dimensional gel electrophoresis and Western blots, probed with anti-α-tubulin monoclonal antibodies, polymorphic α-tubulins (isoforms) were compared in brains and follicle-enclosed oocytes of northern (Rana pipiens) and southern (R. berlandieri) frogs. Oocyte tubulin in both species had isoforms with greater ranges of isoelectric point (pI) than those of brain tubulins; in particular, the oocyte tubulin pIs ranged further into the acidic region of the isoelectric-focusing gels than corresponding brain tubulin. This difference may, in part, be responsible for the previously reported assembly differences between oocyte tubulin (undetectable assembly) and brain tubulin (high assembly). Isoforms of α-tubulin with relat ively acidic pI were more abundant in northern frog brain and oocyte soluble extracts than in analogous extracts from southern frogs. Furthermore, additional acidic α-tubulin isoforms were found in progesterone-treated oocytes (i.e., eggs), indicating increased heterogeneity of acidic a-tubulin isoforms during oocyte meiotic maturation. Among northern frog oocyte soluble components fractionated on Superose-6b columns, tubulin complexes with apparent molecular mass of about 1800 kDa were found to contain acidic α-tubulin isoforms while the putative oligomeric tubulins with an apparent molecular mass of about 250 kDa contained an additional relatively basic α-tubulin isoform. The acidic α-tubulin isoforms, therefore, are proposed to be associated with cold-adaptable cells of brain and oocytes, and may also be involved in stabilization of large soluble tubulin complexes in oocytes of the northern frog. Received 1 October 2002; accepted 9 October 2002 RID="*" ID="*"Corresponding author.     

Changes in cAMP concentration in the rat preoptic area during synchronized and desynchronized sleep

cAMP concentration was found to be significantly lower during desynchronized sleep than during synchronized sleep in the preoptic area of rats kept at normal laboratory temperature. No significant changes in cerebral cortex cAMP concentration were observed in the same experimental conditions.     

Magnetic resonance and the human brain: anatomy, function and metabolism

The introduction and development, over the last three decades, of magnetic resonance (MR) imaging and MR spectroscopy technology for in vivo studies of the human brain represents a truly remarkable achievement, with enormous scientific and clinical ramifications. These effectively non-invasive techniques allow for studies of the anatomy, the function and the metabolism of the living human brain. They have allowed for new understandings of how the healthy brain works and have provided insights into the mechanisms underlying multiple disease processes which affect the brain. Different MR techniques have been developed for studying anatomy, function and metabolism. The primary focus of this review is to describe these different methodologies and to briefly review how they are being employed to more fully appreciate the intricacies associated with the organ, which most distinctly differentiates the human species from the other animal forms on earth. Received 1 November 2005; received after revision 11 January 2006; accepted 25 January 2006     

Morphology of the carnation-light synthetic lethal focus inDrosophila melanogaster

Summary A histological study of the carnation-light lethal focus revealed morphological abnormalities in brain tissue. The ratio of core width to total brain width and brain texture consistently differed between lethal (car-lt) and their non-lethal sibs.