Sex-dependent and sex-independent distribution of the beta-subunit of nerve growth factor in the central nervous and peripheral tissues of mice

Sex-related Differences in Gene Expression in Salivary Glands of BALB/c Mice

Sex-related differences exist in the structure and function of the major glands in a variety of species. Moreover, many of these variations appear to be unique to each tissue. We hypothesized that this sexual dimorphism is due, at least in part, to gland-specific differences in gene expression between males and females. Glands were collected from male and female BALB/c mice (n = 5/sex/experiment), and total RNA was isolated. Samples were analyzed for differentially expressed mRNAs with CodeLink microarrays, and data were evaluated by GeneSifter. Our results demonstrate that significant (P < 0.05) sex-related differences exist in the expression of numerous genes in the major salivary glands, and many of these differences were tissue-specific. These findings support our hypothesis that sex-related differences in the salivary glands are due, at least in part, to tissue-specific variations in gene expression.

NGF, brain and behavioral plasticity

Nerve Growth Factor (NGF) was initially studied for its role as a key player in the regulation of peripheral innervations. However, the successive finding of its release in the bloodstream of male mice following aggressive encounters and its presence in the central nervous system led to the hypothesis that variations in brain NGF levels, caused by psychosocial stressor, and the related alterations in emotionality, could be functional to the development of proper strategies to cope with the stressor itself and thus to survive. Years later this vision is still relevant, and the body of evidence on the role of NGF has been strengthened and expanded from trophic factor playing a role in brain growth and differentiation to a much more complex messenger, involved in psychoneuroendocrine plasticity.

The NGF saga: from animal models of psychosocial stress to stress-related psychopathology

The role of the neurotrophins Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF) has been expanding over the last years from trophic factors involved in brain growth and differentiation, to much more complex messengers, involved in psycho-neuro-endocrine adaptations. Much of this research stems from a series of studies inspired by the life-long work of the Nobel laureate Rita Levi-Montalcini. A new field of research started when NGF was found to be released in the bloodstream as a result of psychosocial stressors in male mice. Subsequent studies have shown that, in humans, highly arousing situations also result in increased blood levels of NGF, underlying the unique role of this neurotrophin, compared to other neuroendocrine effectors, and its sensitivity to environmental variables endowed by a social nature. Data are reviewed to support the hypothesis that this neurotrophic factor, together with BDNF, could be involved in the neurobiological changes underlying physiological and pathological reactions to stress that can result in increased vulnerability to disease in humans, including risk for anxiety disorders, or in the complex pathophysiology associated with mood disorders. Indeed, numerous data indicate that neurotrophins are present in brain hypothalamic areas involved in the regulation of hypothalamic-pituitary-adrenal axis, circadian rhythms and metabolism. In addition, there is now evidence that, in addition to the nervous system, neurotrophins exert their effects in various tissue compartments as they are produced by a variety of non-neuronal cell types such as endocrine and immune cells, adipocytes, endothelial cells, keratinocytes, thus being in a position to coordinate brain and body reactions to external challenges. Aim of this review is to discuss the evidence suggesting a role for neurotrophins as multifunctional signaling molecules activated during allostatic responses to stressful events and their involvement in the complex pathophysiology underlying stress-related psychopathology.

Effects of NGF, NT-3 and GDNF family members on neurite outgrowth and migration from pelvic ganglia from embryonic and newborn mice

Background

Pelvic ganglia are derived from the sacral neural crest and contain both sympathetic and parasympathetic neurons. Various members of the neurotrophin and GDNF families of neurotrophic factors have been shown to play important roles in the development of a variety of peripheral sympathetic and parasympathetic neurons; however, to date, the role of these factors in the development of pelvic ganglia has been limited to postnatal and older ages. We examined the effects of NGF, NT-3, GDNF, neurturin and artemin on cell migration and neurite outgrowth from explants of the pelvic ganglia from embryonic and newborn mice grown on collagen gels, and correlated the responses with the immunohistochemical localization of the relevant receptors in fixed tissue.

Results

Cell migration assays showed that GDNF strongly stimulated migration of tyrosine hydroxylase (TH) cells of pelvic ganglia from E11.5, E14.5 and P0 mice. Other factors also promoted TH cell migration, although to a lesser extent and only at discrete developmental stages. The cells and neurites of the pelvic ganglia were responsive to each of the GDNF family ligands – GDNF, neurturin and artemin – from E11.5 onwards. In contrast, NGF and NT-3 did not elicit a significant neurite outgrowth effect until E14.5 onwards. Artemin and NGF promoted significant outgrowth of sympathetic (TH+) neurites only, whereas neurturin affected primarily parasympathetic (TH-negative) neurite outgrowth, and GDNF and NT-3 enhanced both sympathetic and parasympathetic neurite outgrowth. In comparison, collagen gel assays using gut explants from E11.5 and E14.5 mice showed neurite outgrowth only in response to GDNF at E11.5 and to neurturin only in E14.5 mice.

Conclusion

Our data show that there are both age-dependent and neuron type-dependent differences in the responsiveness of embryonic and neo-natal pelvic ganglion neurons to growth factors.

Integrin alpha9 beta1 is a receptor for nerve growth factor and other neurotrophins

The integrin alpha9beta1 is a multifunctional receptor that interacts with a variety of ligands including vascular cell adhesion molecule 1, tenascin C and osteopontin. We found that this integrin is a receptor for nerve growth factor (NGF) and two other neurotrophins, brain-derived neurotrophic factor and NT3, using a cell adhesion assay with the alpha9SW480 cell line. Interaction of alpha9beta1 with NGF was confirmed in an ELISA assay by direct binding to purified integrin. alpha9beta1 integrin binds to neurotrophins in a manner similar to another common neurotrophin receptor, p75(NTR) (NGFR), although alpha9beta1 activity is correlated with induction of pro-survival and pro-proliferative signaling cascades. This property of alpha9beta1 resembles the interaction of NGF with a high affinity receptor, TrkA, however, this integrin shows a low affinity for NGF. NGF induces chemotaxis of cells expressing alpha9beta1 and their proliferation. Moreover, alpha9beta1 integrin is a signaling receptor for NGF, which activates the MAPK (Erk1/2) pathway. The alpha9beta1-dependent chemotactic ability of NGF appears to result from the activation of paxillin.

Distribution and immunohistochemical localization of GDNF protein in selected neural and non-neural tissues of rats during development and changes in unilateral 6-hydroxydopamine lesions

The tissue distribution of glial cell line-derived neurotrophic factor (GDNF) during development and changes in GDNF levels by unilateral 6-hydroxydopamine lesions were investigated in rats using a newly established enzyme immunoassay system and by immunohistochemistry. The detection limit of the assay was 0.3 pg/0.2 ml and the system recognized glycosylated mature GDNF. Concentrations of GDNF were relatively high in the kidney and testis during the embryonic and neonatal periods, respectively, and decreased with age. In the striatum, hippocampus and brain stem, GDNF reached a maximal level at around postnatal day 14. However, brain levels were generally lower than those in non-neural tissues. In the CNS, GDNF immunoreactivity was observed in striatal neurons, pyramidal neurons in the hippocampus and the Vth layer of the cortex, large neurons in the diagonal band and brain stem, and spinal motor neurons. It was also evident in several non-neural, tissue-specific cells, such as cells in the renal collecting ducts and distal tubules, and testicular Sertoli cells. Destruction of nigral dopaminergic neurons by 6-hydroxydopamine enhanced the levels of striatal GDNF protein, with apparent involvement of astrocytes. These results suggest that GDNF is normally synthesized in neurons, but may also be produced by astroglial cells in damaged brains.

Levels of neurotrophic factors in the hippocampus and amygdala correlate with anxiety- and fear-related behaviour in C57BL6 mice

The present study tested whether individual differences in anxiety- and fear-related behaviour are associated with between-subjects variation in postmortem brain levels of selected neurotrophic factors. Naïve C57BL6/J mice of both sexes were subjected either to an elevated plus maze test or to a Pavlovian fear conditioning paradigm. Two days after behavioural assays, the mice were sacrificed for postmortem quantification of the protein levels of brain derived neurotrophic factors (BDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3) in the hippocampus and amygdala. Significant correlations between behavioural measures and postmortem regional neurotrophic factor contents were revealed. The magnitude of anxiety-like behaviour in the elevated plus maze was positively related to dorsal hippocampal BDNF levels, but negatively related to NGF levels in dorsal hippocampus and in the amygdala. On the other hand, the expression of conditioned fear is positively related to amygdala BDNF and NGF levels, and to dorsal hippocampal NGF levels. Our results add to existing reports in human as well as in animals of correlation between anxiety trait and gross measures of hippocampal volume or activation levels. Moreover, a distinction between spontaneous and learned (or conditioned) anxiety/fear would be relevant to the identification of neurotrophin signalling mechanisms in the hippocampus and amygdala implicated in anxiety and related psychopathology.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Neurotrophins in murine viscera: a dynamic pattern from birth to adulthood

There is growing evidence that target-derived neurotrophins regulate the function of visceral neurons after birth. However, the postnatal profile of neurotrophin supply from internal organs is poorly described. In this study, we compared neurotrophin concentrations in lysates of murine peripheral target tissues (lung, heart, liver, colon, spleen, thymus, kidney and urinary bladder) at different time points after birth. In most organs, there was a decrease of neurotrophin concentrations in the first weeks after birth. In contrast, there were characteristic increases of specific neurotrophins during adolescence or adulthood. These increases were found for nerve growth factor (NGF) in the heart, thymus, kidney and liver, for brain-derived neurotrophic factor (BDNF) in the lung, and for neurotrophin-3 (NT-3) in the colon. In conclusion, we show that neurotrophins display a very differential and dynamic profile in internal organs after birth.

NT-4 protein is localized in neuronal cells in the brain stem as well as the dorsal root ganglion of embryonic and adult rats

We have newly established a sensitive, two-site enzyme immunoassay system for neurotrophin-4 (NT-4) and investigated its tissue distribution in the rat nervous system. The minimal limit of detection of the assay is 0.3 pg/0.2 mL of assay mixture. Concentrations of NT-4 were found to be extremely low in all brain regions, irrespective of the animal age, the highest level being found in the brain stem of 40-day-old rats, at 0.12 ng/g wet weight. NT-4 levels in young adult rats were significantly lower in the thalamus and higher in the olfactory bulb, neocortex, hypothalamus and brain stem than respective levels in 1-week-old rats. NT-4 immunoreactivity was strong in large neurons of the red nucleus and pontine reticular nucleus as well as the locus coeruleus, and moderate in cells in the mesencephalic trigeminal nucleus and interstitial nucleus of the medial longitudinal fasciculus. In the rat embryo, stong staining of NT-4 was detected in cells of regions corresponding to the midbrain/pons from E11.5 through E15.5. The intensity was decreased after E13.5 when the cytoplasm of cells in the medulla oblongata, fibers of the cerebellar primordium, and both cells and fibers of the dorsal root ganglion were also stained. Concentrations of NT-4 were detected in regions including the hindbrain and the dorsal root ganglion. Immunoblotting of NT-4-immunoreactive proteins extracted from these two regions revealed a band corresponding to mature NT-4 with a molecular mass of approximately 14 kDa. Kainic acid and another glutamte agonist, (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid did not affect NT-4 levels in the hippocampus. The present results show NT-4 to be localized in very limited brain cells and fibers from the embyonic period through to the young adult, suggesting specific roles in brain functions.

Activity-dependent change in the protein level of brain-derived neurotrophic factor but no change in other neurotrophins in the visual cortex of young and adult ferrets

Neurotrophins are suggested to play a role in activity-dependent plasticity of visual cortex during the critical period of postnatal development. Thus, the concentration of neurotrophins in the cortex is expected to change with development and/or with alteration in neuronal activities. To test this, we measured protein levels of nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin-4/5 in visual cortex of young (postnatal day 38-46, at the peak of the critical period) and adult ferrets with two-site enzyme-immunoassay systems. Measurements were carried out also in somatosensory cortex, hippocampus and cerebellum as control. With development the level of brain-derived neurotrophic factor did not significantly change, while those of the other neurotrophins changed in the visual cortex. A blockade of visual inputs for 24 h by an injection of tetrodotoxin into both eyes significantly decreased brain-derived neurotrophic factor protein level in the visual cortex, but not in the other regions in both young and adult ferrets. On the other hand, no significant decrease was seen in the protein level of the other neurotrophins in the visual cortex of young and adult ferrets. A monocular injection of tetrodotoxin in young ferrets resulted in the reduction of brain-derived neurotrophic factor by approximately half that by binocular injection. The degree of the decrease in the contralateral cortex to the injected eye was significantly larger than that in the ipsilateral cortex, reflecting that the contralateral eye is dominantly represented in the cortex in ferrets. Blockade of cortical neuronal activities by a GABA(A) receptor agonist led to a remarkable reduction of brain-derived neurotrophic factor protein in the visual cortex. These results suggest that the level of brain-derived neurotrophic factor protein in visual cortex is regulated by activities of cortical neurons.

Testosterone and nerve growth factor have distinct but interacting effects on structure and neurotransmitter expression of adult pelvic ganglion cells in vitro

Circulating testosterone has potent effects on the structure and function of many pelvic ganglion cells in adult rats in vivo. However not all androgen-sensitive pelvic neurones possess androgen receptors and testosterone effects may therefore be indirect, by an action on the target organs. Here we have examined if testosterone influences neuronal structure in vitro in pelvic ganglion cells cultured from adult male rats. We have also used multiple label immunofluorescence to monitor the expression of transmitter-synthesising enzymes and peptides under various culture conditions. Testosterone was a more potent stimulant of noradrenergic soma growth in culture than nerve growth factor. Whereas nerve growth factor increased the number, branching and length of neurites, testosterone stimulated growth of a small number of very short processes, each of which bore numerous short protrusions. Testosterone also impeded the longer neurite growth induced by nerve growth factor. Many pelvic ganglion cells altered their expression of transmitters/neuropeptides under different culture conditions. In particular, under control conditions or during nerve growth factor treatment, vasoactive intestinal peptide was up-regulated in noradrenergic and cholinergic neurones; testosterone impeded this up-regulation in noradrenergic neurones. Choline acetyltransferase immunoreactivity could only be visualised when nerve growth factor was present in the cultures, and cholinergic neurones showed less neurite outgrowth than noradrenergic neurones under all culture conditions. Nerve growth factor did not stimulate levels of this enzyme as strongly if testosterone was present. This study has shown that testosterone has potent effects on the structure of many pelvic ganglion cells in vitro. It is possible that these effects are mediated indirectly, e.g. by stimulating glial-derived substances, however our results suggest that the effects are not mediated by nerve growth factor. The results also show that testosterone influences some of the actions of nerve growth factor, suggesting that there may be complex interactions between steroid signalling and neurotrophic factors in maintaining neuronal structure and function in vivo.

Distribution of yieldin, a regulatory protein of the cell wall yield threshold, in etiolated cowpea seedlings

We examined the distribution and the immunohistochemical localization of yieldin in etiolated cowpea seedlings with an anti-yieldin antibody. An immunoblotting analysis revealed that the yieldin was located in the aerial organs (plumule, epicotyl and hypocotyl) but not in the roots. The intensity of the yieldin signal in the hypocotyls was highest in the apical pre-elongation region (the hook region) and decreased toward the elongated mature base indicating that the yieldin disappeared with the ceasing of cell elongation. Tissue-print immunoblotting analysis using hypocotyls in different germination stages supports this view because the apical yieldin-rich regions, just beneath the cotyledonary node (the hook and rapidly elongating regions), acropetally migrated together with hypocotyl elongation. Immunohistochemical microscopy demonstrated that yieldin was localized in the cell walls of the cortex and epidermis of the germ axes. The present results are consistent with the view that yieldin participates in the regulation of cell wall yielding during elongation growth.

Neurotrophin-3 controls proliferation of granular precursors as well as survival of mature granule neurons in the developing rat cerebellum

Levels of neurotrophin-3 markedly decrease in the rat cerebellum after the first 10 days of life, suggesting an importance during early development. To further examine the effect of neurotrophin-3 on the developing cerebellum, we injected a monoclonal antibody against neurotrophin-3 into the lateral ventricle of 7.5-day-old rats. The resultant depletion of neurotrophin-3 caused a significant decrease in cerebellar wet weights noted at 7 and 23 days thereafter. Other changes noted 48 h after injection of monoclonal antibodies against neurotrophin-3 included reduced incorporation of bromode-oxyuridine into granule neurons in the external germinal layer, an elevated density of atrophic neurons that had just migrated under the Purkinje cell layer, and an increased number of apoptotic neurons in the internal granule cell layer. These changes were limited to the central lobe. The concentration of neurotrophin-3 protein in the posterior region, including the central lobe, was about four- and threefold higher than that in the anterior region of the cerebellum of 9.5- and 30-day-old rats, respectively. Immunocytochemical examination showed higher amounts of neurotrophin-3 protein in the central lobe than in the anterior lobe. Our results provide evidence that neurotrophin-3 regulates the proliferation of granule precursors and supports the survival of mature granule neurons in restricted lobules, suggesting an involvement in limited regions at a specific stage in development of the rat cerebellum.

Brain-derived neurotrophic factor, nerve growth and neurotrophin-3 selected regions of the rat brain following kainic acid-induced seizure activity

Changes in levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3) in various regions of the rat brain following kainic acid-induced seizure activity were investigated. BDNF protein, as measured by a two-site enzyme immunoassay, increased transiently 12-24 h after the intraperitoneal administration of kainic acid to 61.6 ng/g wet weight in the hippocampus (approximately 10-fold increase), 19.5 ng/g in the piriform plus entorhinal cortex (approximately 10-fold) and 8.2 ng/g in the olfactory bulb (approximately 16-fold), and then rapidly decreased. Increases of 2- to 4-fold in levels of BDNF were also detected in the septum, cerebral cortex, striatum and hypothalamus, but not in the cerebellum. In contrast, levels of NGF and NT-3 decreased 24 h after the administration of kainic acid. Western and Northern blotting analyses of hippocampal tissues, respectively, revealed increase in levels of a 14-kDa protein corresponding to BDNF and its mRNA at both 4.2 and 1.4 kb. Hippocampal mRNAs for NGF and NT-3 increased and decreased, respectively, in kainic acid-treated rats. Immunohistological investigations showed that, in the hippocampus, the administration of kainic acid enhanced a homogeneous immunoreactivity of BDNF in the polymorph inner layer (the stratum radiatum of the CA3/CA4 regions and the hilar region) and in granule cells of the dentate gyrus. BDNF protein was found in neurons, but not at all in glial cells or in blood vessels, and was localized in the cytoplasm, the nucleoplasm and the primary dendrites of neurons as well as in perisynaptic extracellular spaces, but hardly in their axons. Our results show that kainic acid treatment increases levels of BDNF, but not NGF or NT-3, in various regions of the rat brain, other than the cerebellum. Also, the majority of BDNF newly synthesized by hippocampal granule neurons is secreted into the perisynaptic extracellular space in the polymorph inner layer of the dentate gyrus, supporting an autocrine-like role for the factor in synaptic functions.

High potassium enhances secretion of neurotrophic factors from cultured astrocytes

Elevation of extracellular potassium concentration ([K+]o) in the central nervous system (CNS), which is observed such after physiological stimuli and during ischemia, is known to be regulated by astrocytes. We suspected that in response to increased [K+]o, astrocytes might secrete some neurotrophic factor(s) to promote the survival of active and/or ischemically damaged neurons. In the present study, we examined neurotrophic activity contained in HK-ACM, i.e., astrocyte-conditioned medium (ACM) obtained after culturing astrocytes in 40 mM potassium-containing medium (HK medium). Addition of HK-ACM to basal forebrain cultures from postnatal 2-week-old (P2w) rats increased both the choline acetyltransferase (ChAT) activity (4.40-fold) and the number of ChAT-positive neurons (2.01-fold) as compared with non-conditioned HK medium. On the other hand, the neurotrophic effects of LK-ACM, i.e., ACM collected after culturing astrocytes in 4 mM potassium-containing medium (LK medium), were much weaker (2.85- and 1.41-fold for ChAT activity and number of ChAT-positive neurons, respectively) than those of HK-ACM. The neurotrophic effects of ACMs increased in a manner dependent on potassium concentration and on astrocyte culture time. Addition of an antibody against nerve growth factor (NGF) neutralized the neurotrophic effects of HK- and LK-ACMs. Direct quantification of NGF protein in ACMs by the two-site ELISA method demonstrated that a high concentration of potassium enhanced NGF secretion from cultured astrocytes. These results suggested that astrocytes secrete NGF in response to [K+]o elevation in the CNS.

An enhanced conversion from tightly bound to loosely bound form of NGF in selected regions of brains from male mice

Most of the nerve growth factor (NGF) protein in the rat and mouse brain is readily extractable in the presence of guanidine hydrochloride as is the case of brain-derived neurotrophic factor. In the present study, we measured amounts of NGF that could be extracted in the presence and absence of 1 M guanidine hydrochloride from various regions of the brains of male and female mice. About 14% of the total NGF in the hippocampus from female mice at 4 months of age could be extracted without 1 M guanidine hydrochloride (designated loosely bound NGF; about 32% in the rat hippocampus) and the remainder only in its presence (designated tightly bound NGF). The molecular masses of the NGF-immunoreactive protein in both cases were approximately 14 kDa. There were significant differences in respective concentrations of total NGF (the loosely bound plus tightly bound NGF) in the hypothalamus and hypophysis, but not in other brain regions, between male and female mice at 4 months of age. However, levels of loosely bound NGF in the cerebellum and olfactory bulb from males were significantly higher than those in the same regions from females. This difference resulted in two-fold higher ratios of the concentrations of loosely bound to total NGF in males as compared to females. On the other hand, the ratio in the hypophysis was close to unity in both sexes. The concentrations of loosely bound NGF in the hippocampus and cerebral cortex decreased slightly with age in both males and females. Levels of loosely bound NGF increased significantly from 2 to 12 months after birth in the whole brain, olfactory bulb, cerebellum, hypothalamus and hypophysis to a greater extent in males than in females. Thus, it is suggested that high ratios of loosely bound to total NGF in selected regions of brains from male mice are due to an enhanced conversion from tightly to loosely bound form, which is considered to be regulated by androgens (see Brain Res. 322, 112-117, 1990). They may also influence the total NGF expression.

Two types of brain chondroitin sulfate proteoglycan: their distribution and possible functions in the rat embryo

The distribution of neurocan-like and 6B4 proteoglycan-like immunoreactivities in the rat embryo was investigated from gestational days 10.5-15.5 with monoclonal antibody 1G2 or 6B4 that immunoreacted with neurocan and 6B4 proteoglycan, respectively. In the brain region, the leptomeningeal layer in the myelencephalon, metencephalon, diencephalon or telencephalon was first stained with monoclonal antibody 1G2 at embryonic day 12.5. In the spinal cord, monoclonal antibody 1G2 stained the regions corresponding to the boundary caps (designated the boundary caps) after embryonic day 11.5 and the roof plate after embryonic day 12.5. The intensity of staining in the boundary caps reached a maximum at embryonic day 13.5, at around the time when the axons from the dorsal root ganglia reach this region. However, the points of contact of the axons with the boundary caps were hardly stained. By contrast, the roof plate was most strongly and widely stained at embryonic day 14.5, at around the time when the axons enter the spinal cord. Western blotting of preparations from the spinal cord that included the boundary caps revealed the presence of neurocan in this region. Thus, it is likely that neurocan serves as a barrier molecule to regulate the direction of axonal growth from the dorsal root ganglia. By contrast, in addition to staining of the future brain and spinal cord, monoclonal antibody 6B4 stained the trigeminal and sympathetic ganglia in the rat embryo on and after embryonic day 12.5, as well as the vestibular, facial and dorsal root ganglia after embryonic day 12.5. In studies in tissue culture, monoclonal antibody 6B4 prevented the inhibitory effects of 6B4 proteoglycan on the proliferation of PC12D cells. No immunostaining with monoclonal antibody 6B4 was observed in cells that had incorporated bromodeoxyuridine in vivo. Possible functions of 6B4 proteoglycan in the rat embryo are discussed.

Age-related changes in levels of brain-derived neurotrophic factor in selected brain regions of rats, normal mice and senescence-accelerated mice: a comparison to those of nerve growth factor and neurotrophin-3

Age-related changes in the levels of brain-derived neurotrophic factor (BDNF) in selected regions of brains from rats, normal mice and senescence-accelerated mice were compared to those of nerve growth factor (NGF) and neurotrophin-3 (NT-3). The concentration of BDNF increased with age in the rat hippocampus while it decreased in the rat cerebral cortex. The level of BDNF in the hippocampus from aged rats was about 260%, of that in the same region from young adult rats. A strong staining with antibodies specific for BDNF was observed in the hilus of the dentate gyrus in the hippocampus from aged rats. By contrast, BDNF levels were significantly lower in four brain regions from aged rats as compared to young adult rats (30, 56, 52 and 52%, lower in the septum, cerebral cortex, cerebellum and striatum, respectively). Patterns of age-related changes in the level of BDNF in the mouse hippocampus. cerebral cortex, cerebellum and olfactory bulb were similar to those in the respective regions from rats. In rats, the concentration of NGF decreased with age in the cerebral cortex but remained unchanged in the hippocampus, cerebellum and olfactory bulb. In mice, levels of NGF increased in all four brain regions from 1 to 18 months after birth. The concentrations of NT-3 increased and decreased with age in the rat cerebral cortex and cerebellum, respectively, while minimal changes were observed in the rat hippocampus and olfactory bulb as was also true in mice. In senescence-accelerated mice with memory disturbances, no marked increases in levels of NGF and BDNF in the hippocampus and in the level of NT-3 in the cerebral cortex were found. Thus, increases in levels of BDNF and NT-3 occurred in the murine hippocampus and cerebral cortex, respectively, during normal aging, but not during aging of mice with pathological changes.

Ciliary neurotrophic factor arrests muscle and motoneuron degeneration in androgen-insensitive rats

Steroid hormones and neurotrophic factors exert profound and widespread effects on the developing nervous system, including regulation of the size, connectivity, and survival of neurons. Androgenic control of the survival of motoneurons in the spinal nucleus of the bulbocavernosus (SNB) of rats has been well documented. We previously found that ciliary neurotrophic factor (CNTF) mimics many effects of androgen on the developing SNB. Whether effects of CNTF depend on the presence of a functional androgen receptor was evaluated in the present study. Androgen-insensitive male rats bearing the testicular feminization mutation, Tfm, and female litter-mates were treated with CNTF or with vehicle alone from embryonic day 22 through postnatal day 3. On postnatal day 4 SNB cell number was elevated in both groups receiving CNTF. Volumes of the bulbocavernosus (BC) and levator ani (LA) muscles, targets of SNB motoneurons, were also markedly increased by CNTF. Since the BC appears to degenerate completely in untreated females, these results indicate that CNTF can delay or prevent muscle fiber death. The relative sparing of muscles and motoneurons did not differ for Tfm males and females, demonstrating that effects of CNTF on the SNB neuromuscular system do not require functional androgen receptors.

Chondroitin sulphate proteoglycans in the rat brain: candidates for axon barriers of sensory neurons and the possible modification by laminin of their actions

The addition of chondroitin sulphate proteoglycans (CSPGs), purified from the rat brain, to the culture medium of PC12D cells inhibited their proliferation and neurite outgrowth. Therefore, we investigated the effects of several extracellular components on the inhibitory actions of CSPGs on PC12D cells, as well as their immunocytochemical distribution in the rat embryo to determine whether the findings in vitro could be reproduced in vivo. Coating of the substratum with polylysine was necessary for the appearance of the inhibitory effects of brain CSPGs on PC12D cells. The additional pretreatment of polylysine-coated dishes with laminin or fibronectin promoted the outgrowth of neurites from PC12D cells. Laminin and fibronectin, but not collagen (types I and IV) and CELL-TAK (cell adhesion molecules), prevented the inhibitory effects of brain CSPGs in a concentration-dependent manner. Doses producing 50% reduction by laminin (or fibronectin) of the CSPG effects were 1.5 (or 25) micrograms/ml for neurite outgrowth and 2.2 (or 28) micrograms/ml for proliferation. The ratio of dish-attached CSPGs to laminin necessary for 50% reduction was about approximately 50:1 (wt/wt). Laminin from any source had the same effect. Brain CSPGs also obviously impeded the growth of fibres from dorsal root ganglion explants and primary cultured dorsal root ganglion neurons. Neurocan (a major CSPG in the brain)-like immunoreactivity was detected in the boundary caps and roof plate in the rat embryo at 13.5 days of gestation, when DRG neurons were extending their axons to the neural tube. The distributions of laminin and tenascin appeared, respectively, to be slightly and considerably different from that of neurocan.(ABSTRACT TRUNCATED AT 250 WORDS)

A subpopulation of large neurons of the sympathetic superior cervical ganglion innervates the NGF-rich submandibular salivary gland in young adult and aged mice

One of the main target organs of the sympathetic superior cervical ganglion (SCG) is the submandibular salivary gland, which in male mice has a high concentration of endogenous NGF. To study the subpopulation of SCG neurons which innervate the submandibular glands in young adult and aged mice, a retrograde tracing with a fluorescent dye Fluoro-Gold (Fluorochrome, Englewood, CO, USA) was performed. Fluoro-Gold was introduced into the base of the submandibular salivary gland in anaesthetized animals. Four days later, both ipsilateral and contralateral SCG were studied. The results of the tracing were as follows: (a) in both young adult and aged mice about 45% of the sympathetic neurons of the SCG innervate the ipsilateral submandibular salivary gland; (b) the neurons innervating the submandibular gland form a subpopulation of large-sized neurons; (c) in young adult mice some 10% of SCG neurons innervate the contralateral SCG, while in aged mice only 1-2% have the same effect.

Age-related changes in levels of the beta-subunit of nerve growth factor in selected regions of the brain: comparison between senescence-accelerated (SAM-P8) and senescence-resistant (SAM-R1) mice

Senescence-accelerated mice (SAM-P8) are characterized as mice in which aging is accelerated and memory disturbances occur. In several regions in the brain of SAM-P8 mice at 2, 4 and 8 months of age, we examined the concentrations of the beta-subunit of nerve growth factor (beta-NGF) and nine kinds of proteins such as S100 beta and alpha B-crystallin, and compared them with those in senescence-resistant mice (SAM-R1, as controls) at corresponding ages. Levels of beta-NGF in the hippocampus of SAM-R1 and SAM-P8 mice were reduced at 8 months of age. However, the decrease was more conspicuous in SAM-R1 than in SAM-P8, resulting in a significant difference between them (P < 0.01). The concentrations of beta-NGF in the cerebral cortex and cerebellum decreased to some extent with age in the control mice while it remained unchanged in the mutant mice. By contrast, the olfactory bulbs from SAM-R1 and SAM-P8 retained almost constant levels of beta-NGF during the first 8 months. However, its level was already higher in SAM-P8 at 2 months than in SAM-R1. Among nine proteins measured here, the acceleration of age-related increase was apparent in the levels of S100 beta and Mn-SOD in the cerebral cortex from SAM-P8. By contrast, the cerebral cortex and cerebellum from SAM-P8 showed tendencies to contain significantly high levels of alpha B-crystallin. These results suggest, at least, the presence of fibrous gliosis at quite an early age as well as the acceleration of senescence, in selected regions of the brain of SAM-P8.

Motor neurons in Onuf's nucleus and its rat homologues express the p75 nerve growth factor receptor: sexual dimorphism and regulation by axotomy

The present study establishes that populations of neurons in the lumbosacral cord, which innervate pelvic striated muscles, express p75NGFR throughout their life spans. These neuronal groups comprise the Onuf's nucleus in humans and its principal rat homologues, dorsolateral (DL) and dorsomedial (DM) nuclei, as well as the cremasteric (CRE) nucleus. The p75NGFR in these neurons is localized in the rough endoplasmic reticulum, Golgi complex, and lysosomes. Almost all neurons that project to striated perineal muscles in the male rat express p75NGFR; very low levels of p75NGFR are detected in neurons that innervate perineal sphincters of the female. In the female rat, p75NGFR expression is masculinized with perinatal androgen treatment. In addition, the expression of p75NGFR in DM and DL neurons in the adult is up-regulated by injury (i.e., pudendal axotomy) but is not influenced by gonadectomy. The results of this study establish that neurons of Onuf's nucleus and its rat homologues differ from general somatic motor neurons in that they express p75NGFR from early postnatal life (i.e., when all motor neurons express p75NGFR) into the adult (when the former, but not the latter, express the receptor). In view of growing evidence for the role of neurotrophins in the physiology of motor neurons, the above differentiating feature between general somatic and sexually dimorphic motor neurons suggests that p75NGFR may be involved in motor neuron plasticity and may participate in mechanisms by which neurons can protect themselves from degenerative insults.

Regulation by androgen of levels of the beta subunit of nerve growth factor and its mRNA in selected regions of the mouse brain

Our previous studies showed that the concentration of the beta subunit of nerve growth factor (beta-NGF) in nervous tissues is higher in male than in female mice. To identify the brain regions that are affected by androgens, the amounts of beta-NGF protein and its mRNAs were measured in male, female, and castrated male CD-1 mice and testicular feminization mice at 3-4 months of age. Among tissues examined, the hypophysis of males contained the highest average concentration of beta-NGF protein. In most regions of the brain, individual levels were more variable in males than in females. However, after the castration, such variations in beta-NGF levels disappeared. Average levels of beta-NGF protein in males were higher in the cerebellum (eightfold higher), olfactory bulb (12-fold higher), hypothalamus (sixfold higher), and hypophysis (72-fold higher) than those in corresponding regions of females. No significant differences were observed in levels of beta-NGF protein in the hippocampus, cerebral cortex, striatum, septum, and brainstem. The castration of male mice caused a reduction in levels of beta-NGF protein in the hypothalamus and hypophysis, but not in the cerebellum and olfactory bulb, to the female levels. The concentrations of beta-NGF protein in testicular feminization mice were similar to those in female CD-1 mice in all regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in nerve growth factor content of the submaxillary gland in the genetically dystrophic (mdx) mouse

We evaluated the nerve growth factor (NGF) contents in the submaxillary gland of the mdx mouse, a model for Duchenne muscular dystrophy (DMD), and found that the NGF and NGF mRNA contents in this organ, where extraordinarily high amounts of NGF are synthesized and stored independently of development or maintenance of the nervous system, were markedly elevated in the male mdx mouse at 8 and 11 weeks of age. However, the NGF content of this organ in 4-week-old male mdx mice was lower than that of control mice although statistical significance of difference was not observed. In the mdx female mouse, the submaxillary NGF content was significantly lower than that of the normal mouse at 4 weeks of age, but was similar to that of the normal at 8 and 11 weeks of age. The amounts of epidermal growth factor (EGF), another protein that is known to be sexually and developmentally regulated in the mouse submaxillary gland like NGF, was found to be also significantly increased in this organ of the male mdx mouse at 8 and 11 weeks of age, and to be significantly decreased in that of the female mdx mouse at 4 weeks of age. The parallel changes in NGF and EGF contents during development of the submaxillary gland suggest that the mdx mouse suffers from some abnormality in the development of this organ.(ABSTRACT TRUNCATED AT 250 WORDS)

An acceleration of age-related increases in levels of the beta-subunit of nerve growth factor in selected tissues from senescence-accelerated mice (SAM-P/8)

An investigation was made of age-related changes in levels of the beta-subunit of nerve growth factor (beta-NGF) in selected tissues and of testosterone in serum in senescence-accelerated mice (SAM-P/8) and in the control mice (senesence-resistant mice; SAM-R/1). The concentrations of testosterone in serum were higher in SAM-P/8 than in SAM-R/1 at ages 2 and 4 mo. The level of beta-NGF in the thymus from SAM-R/1 increased with age, resulting in a statistically significant difference in its level between mice at ages 2 and 12 mo. By contrast, there was a transient increase in SAM-P/8 at around age 4 mo with a subsequent decrease. Consequently, significant differences were apparent in levels of beta-NGF between the two types of mouse at ages 2 and 4 mo. Similar results were obtained in the adrenal gland and testis. Compared to SAM-R/1 at age 2 mo, the average concentrations of beta-NGF in the hypophysis were higher in SAM-R/1 at ages 4 and 8 mo and in SAM-P/8 at all ages. In other tissues tested, no remarkable differences were detected. Our present results indicate that, in SAM-P/8, the elevation in levels of beta-NGF in the thymus, adrenal gland, testis, and hypophysis occurs in the early period of life compared to the control mice. Possible dysfunction of the disorder of hypophysis is discussed.

Temporal profiles of nerve growth factor beta-subunit level in rat brain regions after transient ischemia

To determine the role of nerve growth factor (NGF) in ischemic brain damage, we measured the temporal and regional changes in the level of NGF in the hippocampal subfields, the cerebral cortex, the striatum, and the septum at 1, 2, 7, and 30 days after transient forebrain ischemia using a highly sensitive sandwich-type enzyme immunoassay system for the beta-subunit of mouse 7S NGF (beta-NGF). We also analyzed glial fibrillary acidic protein immunoreactivity in the hippocampus to ascertain the contribution of reactive astrocytes to NGF production after an ischemic insult. In the CA1 subfield of the hippocampus, the level of beta-NGF decreased slightly 2 days after ischemia (not significant), at which time CA1 pyramidal cell loss began to occur, and increased by 40% 30 days after ischemia (p less than 0.05). A marked increase in glial fibrillary acidic protein-positive astrocytes in the CA1 subfield 2-30 days after ischemia suggests that the reactive astrocytes participated in a gradual increase in the level of beta-NGF after recirculation. The level of beta-NGF in the dentate gyrus decreased transiently 2 days (p less than 0.05) and 7 days (p less than 0.01) after ischemia, followed by recovery to the level of control animals 30 days after ischemia. The level of beta-NGF in the septum gradually decreased 7 days (-27%, p less than 0.05) and 30 days (-43%, p less than 0.01) after ischemia. The levels of beta-NGF in the cerebral cortex and striatum remained unaltered throughout the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sialectomy on the superior cervical ganglion sympathetic neurons in young adult and aged mice

The dependence of superior cervical ganglion (SCG) adrenergic neurons on their target organ submandibular salivary gland containing high concentrations of nerve growth factor was studied in adult and aged male mice. The submandibular salivary glands were removed (sialectomy) either uni- or bilaterally, and the SCG were studied by fluorescence microscopy and histochemically. Catecholamine fluorescence and tyrosine hydroxylase immunoreactivity decreased after sialectomy, suggesting reduced noradrenaline production. Neuronal density was lower in the aged controls than in the young controls. In both age groups, sialectomy reduced the density of catecholamine-producing neurons. In the mouse SCG, there was remarkable heterogeneity in the size of neuronal somata. In aged control mice there was a greater number of large-size neurons than in young adult control mice. Six weeks postoperatively, no large catecholamine-producing neurons could be observed in the ganglia. Yellow autofluorescent lipopigments accumulated with age in the adrenergic neurons. Sialectomy increased the accumulation of lipopigments in both young and aged neurons. Sialectomy resulted in (a) reduced catecholamine fluorescence, (b) reduced tyrosine hydroxylase immunoreactivity, (c) reduced number of catecholamine neurons, (d) increased autofluorescent lipopigment. Ageing resulted in (a) reduced number of neurons, (b) increased ratio of large to small neurons, (c) increased autofluorescent lipopigment. Alterations after sialectomy were more detrimental in the aged ganglia than in the young adult ganglia. The discontinuation of the retrograde supply of nerve growth factor may contribute to these alterations.

Age- and sex-related differences in the nerve growth factor distribution in the rat brain

Levels of the nerve growth factor (NGF) have been measured in various brain regions of young and aged male and female rats of Wistar strain by means of a highly sensitive two-site enzyme immunoassay system for beta-NGF. Among the ten regions examined, the amount of NGF per wet weight of tissue was found to be highest in the hippocampus, irrespective of the sex and age. The NGF concentration in the hippocampus of female rats at 3 months of age was comparable to that of same aged males. Further, there was no significant difference in the NGF levels of the hippocampus between young and age males. However, the NGF level was significantly lower in aged females as compared to that in 3- or 4-month-old females, and hence the marked male-female difference was found in the NGF levels in aged Wistar rats.

Hippocampal NGF levels are not reduced in the aged Fischer 344 rat

The sympathetic sprouting response that occurs in the rat hippocampal formation following septal denervation is reduced in aged rats. Since considerable evidence implicates NGF-like activity in eliciting the sprouting, the simplest explanation for the age-related decline in sympathetic sprouting is a reduction in hippocampal NGF levels. In the present study, hippocampal NGF levels were measured using a 2-site ELISA in four different age groups of Fischer 344 rats. There was no decline in NGF levels with age, nor did we find any differences between male and female rats. This contradicts an earlier report in which a 40% reduction in hippocampal NGF protein levels was found in aged rats. Possible reasons for this discrepancy are discussed. The present results do not support the hypothesis that the age-related decline in sympathetic sprouting is due to a reduction in total hippocampal NGF levels.

Elevated concentrations of beta-nerve growth factor in selected tissues from senescence-accelerated mice (SAM-P/8)

Levels of the beta-subunit of nerve growth factor (beta-NGF) were determined in various tissues from senescence-accelerated mice (SAM-P/8) and compared with those from senescence-resistant control mice (SAM-R/1) at 4 months of age. (1) In SAM-P/8, the testis was 30% larger in terms of wet weight than that from SAM-R/1, whereas the adrenal glands from males and females were smaller than those from the respective controls by 45% and 20%, respectively. (2) About 70% of SAM-P/8 individuals had high concentrations of testosterone in serum (greater than 5ng/ml). (3) In SAM-P/8, endogenous levels of beta-NGF were significantly higher in the adrenal gland (20 and 7 times higher on average in males and females, respectively), in the thymus (100 and 5 times higher in males and females, respectively) and in the testis (500 times higher) than those in the control tissues. In other tissues there were little or no differences in terms of levels of beta-NGF. (4) Morphological changes in the adrenal gland, thymus and testis of SAM-P/8 mice were not as marked as expected from the elevated levels of beta-NGF in these tissues. (5) These results show that, in SAM-P/8 mice at 4 months of age, an elevation in the endogenous level of beta-NGF has already occurred in some peripheral tissues before senescence becomes accelerated.

Intraventricular infusion of epidermal growth factor restores dopaminergic pathway in hemiparkinsonian rats

We assessed the effect of a 35-day delayed intracerebroventricular (ICV) infusion of epidermal growth factor (EGF) on the survival and function of the substantia nigra (SN) dopaminergic neurons after a unilateral mechanical transection of rat nigrostriatal pathway. EGF infusion for 28 days resulted in a twofold increase in the number of surviving tyrosine-hydroxylase (TH)-positive SN neurons and a significant increase in ipsilateral striatal TH-positive fiber staining compared to controls at 200 days following the injury. In addition, there was a persistent enhancement of behavioral recovery, as indicated by a reduction in amphetamine-induced rotations. We conclude that EGF exerts a neurotrophic effect on the dopaminergic neurons in this experimental model of parkinsonism.

Structure and biosynthesis of nerve growth factor

Most of our knowledge about NGF comes from extensive study of the mouse submaxillary gland protein. NGF from this source is isolated as a high molecular weight complex consisting of beta-NGF and two subunits, alpha and gamma, belonging to the kallikrein family of serine proteases. There are few other tissues where NGF is found in sufficient quantities for protein purification and study, although new molecular biological techniques have accelerated the study of NGFs from a variety of species and tissues. Mouse submaxillary gland NGF is synthesized as a large precursor that is cleaved at both N- and C-terminals to produce mature NGF. This biologically active molecule can be further cleaved by submaxillary gland proteases. The roles of the alpha and gamma subunits in the processing of the beta-NGF precursor, the modulation of the biological activity of beta-NGF, and the protection of mature beta-NGF from degradation have been well studied in the mouse. However, the apparent lack of alpha and gamma subunits in most other tissues and species and the existence of a large family of murine kallikreins, many of which are expressed in the submaxillary gland, challenge the relevance of murine high molecular weight NGF as a proper model for NGF biosynthesis and regulation. It is important therefore to identify and characterize other NGF complexes and to study their subunit interactions, biosynthesis, processing, and regulation. This review points out a number of other species and tissues in which the study of NGF has just begun. At this time, there exist many more questions than answers regarding the presence and the functions of NGF processing and regulatory proteins. By studying NGF in other species and tissues and comparing the processing and regulation of NGF from several sources, we will discover the unifying concepts governing the expression of NGF biological activity.

Reduction of nerve growth factor level in the brain of genetically ataxic mice (weaver, reeler)

By a highly sensitive enzyme immunoassay we measured the level of nerve growth factor (NGF) in the cerebellum and cerebrum of the neurologically mutant mice, weaver, reeler and Purkinje cell degeneration (PCD). A significant decrease in NGF level was observed in both cerebellum and cerebrum of weaver and reeler mutants of either sex. However, there was no such difference between normals and mutants in the case of the PCD mice. These results show that weaver and reeler mice have abnormalities of NGF synthesis and/or degradation not only in the cerebellum but also in the cerebrum.

Influences of neonatal and adult exposures to testosterone on the levels of the beta-subunit of nerve growth factor in the neural tissues of mice

In our previous report, we have shown the sex difference in the concentration of the beta-subunit of nerve growth factor (beta-NGF) in the neural and paraneural tissues of mice. In this investigation, we examined the effects of castration of adult males, and of neonatal and/or adult treatments with testosterone on levels of beta-NGF in the several tissues of mice. Castration caused a marked reduction in the levels of serum testosterone and of beta-NGF in the brain, spinal cord and submandibular glands, but not in the pancreas and kidneys. Continuous infusion of testosterone for one week into adult males that had been castrated at 2 months of age restored the level of beta-NGF in the three tissues mentioned above. A single injection of testosterone to 5-day-old female pups to masculinize the brain gave no effect on the level of beta-NGF in any tissue dissected after 4 months. A one-week infusion of testosterone into adult females slightly increased levels of beta-NGF in the brain and spinal cord, but the same treatment of adult females given in advance a single dose of testosterone at 5 days of age caused a significant increase in its levels over those of untreated females. These results suggest that neonatal and adult exposures to testosterone can influence the endogenous concentration of beta-NGF in the brain and spinal cord.