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PubMed2005

Different types of environmental enrichment have discrepant effects on spatial memory and synaptophysin levels in female mice.

Environmental enrichment paradigms that incorporate cognitive stimulation, exercise, and motor learning benefit memory and synaptic plasticity across the rodent lifespan. However, the contribution each individual element of the enriched environment makes to enhancing memory and synaptic plasticity has yet to be delineated. Therefore, the current study tested the effects of three of these elements on memory and synaptic protein levels. Young female C57BL/6 mice were given 3h of daily exposure to either rodent toys (cognitive stimulation) or running wheels (exercise), or daily acrobatic training for 6 weeks prior to and throughout behavioral testing. Controls were group housed, but did not receive enrichment. Spatial working and reference memory were tested in a water-escape motivated radial arm maze. Levels of the presynaptic protein synaptophysin were then measured in frontoparietal cortex, hippocampus, striatum, and cerebellum. Exercise, but not cognitive stimulation or acrobat training, improved spatial working memory relative to controls, despite the fact that both exercise and cognitive stimulation increased synaptophysin levels in the neocortex and hippocampus. These data suggest that exercise alone is sufficient to improve working memory, and that enrichment-induced increases in synaptophysin levels may not be sufficient to improve working memory in young females. Spatial reference memory was unaffected by enrichment. Acrobat training had no effect on memory or synaptophysin levels, suggesting a minimal contribution of motor learning to the mnemonic and neuronal benefits of enrichment. These results provide the first evidence that different elements of the enriched environment have markedly distinct effects on spatial memory and synaptic alterations.

Animals↗
PubMed2006

MAP2 and synaptophysin protein expression following motor learning suggests dynamic regulation and distinct alterations coinciding with synaptogenesis.

Learning a new motor skill can induce neuronal plasticity in rats. Within motor cortex, learning-induced plasticity includes dendritic reorganization, synaptogenesis, and changes in synapse morphology. Behavioral studies have demonstrated that learning requires protein synthesis. It is likely that some of the proteins synthesized during learning are involved in, or the result of, learning-induced structural plasticity. We predicted the expression of proteins involved in neural plasticity would be altered in a learning dependent fashion. Long-Evans rats were trained on a series of motor tasks that varied in complexity, so that the effects of activity could be teased apart from the effects of learning. The motor cortices were examined for MAP2 and synaptophysin protein using Western blotting and immunohistochemistry. Western blotting revealed that expression of MAP2 was not detectably influenced by learning, whereas synaptophysin expression increased on day 1, 3, and 5 of complex motor skill learning. Expression of MAP2 does not seem to indicate difficulty of task or duration of training time, whereas increases in synaptophysin expression, which appear diffusely across the cortex, seem to be correlated with the first 5 days of motor skill learning. Similar findings with GAP-43 suggest the change in synaptophysin may coincide with synapse formation. Immunohistochemistry did not reveal any localized changes in protein expression. These data indicate a difference in learning-induced expression in the mammalian brain compared to reports in the literature, which have often focused on stimulation to induce alterations in protein expression.

Adaptation, Physiological↗
PubMed1999

Reduction of the small synaptic vesicle protein synaptophysin but not the large dense core chromogranins in the left thalamus of subjects with schizophrenia.

BACKGROUND: It has been hypothesized that a lesion in the neuronal circuits of thalamus might contribute to the symptoms in schizophrenia. It has also been suggested that impaired synaptic transmission is an important component of the pathophysiology of schizophrenia. In the present study we assess the synaptic integrity of thalamus by means of examining the protein levels of: (1) synaptophysin, a membrane bound protein of small synaptic vesicles, and (2) chromogranins, a family of soluble secretory proteins stored and released from the secretory large dense-core vesicles. METHODS: The brains of 9 patients with schizophrenia and 9 age-matched control subjects were studied. The levels of synaptophysin and chromogranins were measured by radioimmunoassays. RESULTS: The amount of synaptophysin in the left thalamus was significantly decreased (p = .036) in the schizophrenic group (2655 +/- 605 nmol synaptophysin/mg total protein) compared to the control group (3248 +/- 827 nmol synaptophysin/mg total protein). There were no differences between the groups in the levels of chromogranins, nor in the levels of synaptophysin of the right thalamus. CONCLUSIONS: These findings indicate defect synaptic function in the left thalamus of patients with schizophrenia. This may be the cause of a reduction of synaptic terminals or a defect limited to certain structures of the synapse, namely the small presynaptic vesicles.

Aged↗
PubMed2001

Changes in presynaptic proteins, SNAP-25 and synaptophysin, in the hippocampal CA1 area in ischemic gerbils.

A general consensus exists that the presynaptic terminals in the hippocampal CA1 area are resistant to ischemic stress in spite of the loss of their target cells (CA1 pyramidal neurons). We have verified this by immunostaining and Western immunoblotting using the antibodies for presynaptic proteins, synaptosomal-associated protein of 25 kDa (SNAP-25) and synaptophysin in gerbils after bilateral carotid artery ligature. In the immunohistochemical analysis, decreases in SNAP-25 and synaptophysin immunoreactivities in the strata radiatum and oriens, especially around the apical dendrite of CA1 neurons, and disappearance of SNAP-25 immunoreactivity in the alveus were observed on day 2 after ischemia. On days 7 and 14, SNAP-25-positive granular materials were expressed in the CA1 area, and intense synaptophysin immunoreactivity around surviving CA1 neurons was observed. Western immunoblot analysis revealed significant decreases of SNAP-25 and synaptophysin (about 60% of control levels) on day 2, and then increase of their proteins (130--140% of control levels) on day 14. These results indicate that presynaptic degeneration occurs in the hippocampal CA1 area after ischemia, and it precedes the delayed neuronal death of CA1 neurons. The presynaptic terminal damage may be responsible for some pathological changes in ischemic brains.

Animals↗
PubMed1997

Rab3A immunolocalization in the mammalian vestibular end-organs during development and comparison with synaptophysin expression.

Rab proteins are essential for membrane vesicle docking and fusion and for transport vesicle formation at the presynaptic membrane, a step in the release of neurotransmitters. The vestibular sensory epithelia contain three types of synapses: afferent terminals, efferent endings and possible synaptic contacts between the apex of the afferent nerve calyces and the sensory cells. We report an immunocytochemical codetection of rab3A and synaptophysin in the vestibular end-organs of mouse, between fetal day 14 and adult, and of rat during the postnatal development. During mouse fetal development, rab3A appeared in afferent neurites on F16, and in sensory cells on F19. This was respectively two and five days later than the appearance of synaptophysin-IR in the same compartments. During the late postnatal development and in the adult sensory epithelia, rab3A and synaptophysin were strongly detected in nerve terminals of efferent and possibly afferent nature and in the upper part of the nerve calyces. The presence of rab3A in the nerve calyces is consistent with the putative secretory function of the calyx. In addition, rab3A immunostaining was also present in the sensory cells together with a faint synaptophysin-IR, that had not been described in previous reports [Scarfone, E., Demêmes, D. and Sans, A. J. Neurosci., 11 (1991) 1173-1181.]. The presence of these two proteins in the sensory cells supports the existence of a synaptic vesicle cycle in these cells.

Animals↗
PubMed1997

Developmental expression of synaptophysin, synapsin I and syntaxin in the rat retina.

Expression of synaptophysin, synapsin I and syntaxin was studied immunocytochemically in the developing rat retina using indirect immunoperoxidase technique. In the inner plexiform layer (IPL), syntaxin immunoreactivity appeared at postnatal day 1 (P1) whereas synaptophysin and synapsin I staining were first observed at P2. In the outer plexiform layer (OPL), synaptophysin appeared at P4, while synapsin I and syntaxin appeared at P8. In the case of synaptophysin, a punctate pattern of staining was observed from the time of its appearance (P4) in the OPL and from P12 onwards in the IPL. Synapsin I and syntaxin immunoreactivity in the OPL were of a low intensity throughout the development and in the adult stage. These findings are discussed in relation to synaptogenesis in the rat retina.

Animals↗
PubMed2000

Expressions of amyloid precursor protein, synaptophysin and presenilin-1 in the different areas of the developing cerebellum of rat.

This study reveals the expressions of Alzheimer's disease-related amyloid precursor protein, presenilin-1, and a presynaptic marker protein, synaptophysin, in the archi-, paleo- and neocerebellum during the postnatal development of the rat. The Western blot results demonstrate a gradual increase in the soluble amyloid precursor protein level in the archicerebellum during the first 3 weeks, while in the neo- and paleocerebellum the levels reach a plateau as early as the 1st week. Immunohistochemically, the protein is present in the deep part of the external granule cell layer and the internal granule cell layer in the newborn animal, while in 3-week-old animals the staining appears mainly in the perikarya and dendrites of the Purkinje cells. The level of synaptophysin increases progressively from postnatal day 7 up to 3 weeks in the archi- and paleocerebellum, and up to 6 weeks in the neocerebellum. Immunohistochemically, the amyloid precursor protein staining appears first in the inner part of the molecular layer and in the internal granule cell layer. In a 3-week-old animal, synaptophysin staining is present in all areas of the cerebellar molecular layer and in the internal granule cell layer. The presenilin-1 immunohistochemical reaction appeared equally in the archi-, paleo- and neocerebellum. Much of the staining is present in the glial cells and Purkinje cells. Less immunoreactivity is observed in the Golgi cells and granule cells. It is concluded that the postnatal expressions of soluble and membrane-bound amyloid precursor protein, synaptophysin and presenilin-1 are regulated differently during the ontogenetical development of the archi-, paleo- and neocerebellum of rat. Further, the amyloid precursor protein and presenilin-1 may be present in cells which do not degenerate in Alzheimer's disease.

Aging↗
PubMed2001

Antenatal betamethasone treatment reduces synaptophysin immunoreactivity in presynaptic terminals in the fetal sheep brain.

Knowledge of morphofunctional effects on the fetal brain induced by exogenous glucocorticoids is limited. Recently, we reported alterations of both the neuronal cytoskeleton and electrocortical function in the ovine fetal brain after antenatal betamethasone treatment in doses used in perinatal medicine. In the present study we examined whether these changes are accompanied by morphological alterations of synapses. Chronically instrumented fetal sheep at 0.87 of gestation were treated either with isotonic saline (n=7) or 10 microg/h betamethasone (n=7) over 48 h administered directly to the fetal jugular vein. Paraffin sections of the frontal neocortex, caudate putamen and hippocampus were stained with a monoclonal antibody against synaptophysin, a specific membrane protein of presynaptic vesicles and quantified morphometrically. Synaptophysin-like immunoreactivity (synaptophysin-LI) showed a widespread granular pattern in the neuropil. Betamethasone exposure reduced synaptophysin-LI in the frontal neocortex, caudate putamen and hippocampus by 46.9, 41.0 and 55.4%, respectively, (P<0.05) that was not accompanied by irreversible neuronal damage. These results suggest that clinical doses of betamethasone have acute effects on presynaptic terminals in the fetal sheep brain that could contribute to the altered complexity of electrocortical function that we have shown previously to occur following fetal exposure to betamethasone.

Animals↗
PubMed1997

Pattern of synaptophysin immunoreactivity in the efferent nerve terminals of the guinea pig cochlea.

The goal of the present study was to analyze the distribution of efferent 8th nerve synaptic endings in a surface preparation of the guinea pig cochlea using synaptophysin antibodies. Employing light and confocal microscopy synaptophysin immunoreactivity was found exclusively at the base of the outer hair cells (OHCs) and the inner hair cells (IHCs) axosomatic efferent synapses. Qualitative and quantitative differences were found between the OHCs and the IHCs immunoreactivity. Efferent nerve endings innervating IHCs were comparatively smaller, more numerous and densely packed. Efferent terminals demonstrated a longitudinal gradient for the IHCs and a longitudinal and radial gradient for the OHCs. Quantitative analysis of synaptophysin immunofluorescence demonstrated a higher percentage of efferent terminals innervating the IHCs and the OHCs in the mid and basal segments of the cochlea than in the apical regions. In addition, a radial gradient from the 1st to 3rd row of OHCs was evident. The results from the present study show that the analysis of synaptophysin immunoreactivity on cochlear surface preparations allows the efferent innervation to be determined throughout the entire cochlea. This technique allows for a rapid assessment of the normal cochlea as well as after cochlear insult.

Animals↗
PubMed1997

Giant cells in cortical tubers in tuberous sclerosis showing synaptophysin-immunoreactive halos.

We describe a characteristic pattern of immunoreactivity for synaptophysin in tuberous sclerosis. We analyzed cortical tubers from surgical specimens taken from six patients with tuberous sclerosis, which were obtained by surgical resections for the treatment of intractable seizures. The cortical tubers were characterized by blurred lamination of the cerebral cortex, hypercellularity, and gliotic changes. Neuropil in the cortex of cortical tubers showed reduced immunoreactivity for synaptophysin in all patients. 'Giant cells' were investigated in the cortex and white matter regions of cortical tubers. Some 'giant cells' had neuronal characteristics such as Nissl substance, a centrally placed chromatin-marginated nucleus, prominent nucleolus, positive immunoreactivity for microtubule-associated protein 2, and negative immunoreactivity for glial fibrillary acidic protein. Other 'giant cells' were indeterminate in cell type because they lacked Nissl bodies, distinct nucleolus, consistent immunoreactivity for microtubule-associated protein 2 and glial fibrillary acidic protein. Almost all 'neuronal giant cells' and some of the 'indeterminate giant cells' in the white matter showed intense immunoreactivity for synaptophysin: cell borders were surrounded by an intense immunoreactive halo. In conclusion, these immunohistochemical patterns for synaptophysin assist in characterizing these abnormal cells in the cortical tubers of patients with tuberous sclerosis.

Cerebral Cortex↗
PubMed2002

Reduction of the synaptophysin level but normal levels of glycerophospholipids in the gyrus cinguli in schizophrenia.

The 'membrane hypothesis' of schizophrenia postulates a disturbance in the metabolism and structure of membrane phospholipids resulting in a disturbance in the function of neuronal membrane proteins. Most studies exploring this hypothesis have examined components of peripheral blood. Since it may be questioned if these peripheral measurements reflect changes in the brain, we studied the fatty acid composition of glycerophospholipids in brain tissue. As a marker for synaptic density, we also measured the synaptic vesicle protein synaptophysin. Brain tissue (gyrus cinguli) from 11 schizophrenic patients (mean age 80 +/- 10 years) and 13 controls (mean age 75 +/- 14 years) was examined. The glycerophospholipid fatty acids were determined by gas chromatography. Synaptophysin protein level was determined using quantitative immunoblotting followed by Western blotting. There were no significant differences between the groups in the total or in any individual level of fatty acids, either in the n - 6 or n - 3 series. The level of synaptophysin was significantly p = (0.002) decreased in the schizophrenic group(0.73 + 0.18) as compared with the control group (1.02 + 0.21). The normal pattern and concentration of glycerophospholipids fatty acids found in the present study do not support the membrane hypothesis of schizophrenia. The possibility of a type II error should, however. be considered. On the other hand, the reduced synaptophysin' levels in the gyrus cinguli demonstrate that biological differences can be revealed in this relatively small sample. This also lends further support to the notion that a synaptic disturbance or loss is of importance in the pathogenesis of schizophrenia.

Aged↗
PubMed2000

Role of synaptophysin in exocytotic release of dopamine from Xenopus oocytes injected with rat brain mRNA.

1. The role of synaptophysin in the exocytotic release of dopamine (DA) was examined in Xenopus laevis oocytes injected with rat brain mRNA. 2. The mRNA-injected oocytes showed DA uptake which depended on the incubation time and external DA concentrations. 3. Stimulation with KCl (10-50 mM) of mRNA-injected oocytes preloaded with DA evoked external Ca2+ -dependent release of DA. The noninjected and water-injected oocytes did not produce uptake of DA and stimulation-evoked release of DA. 4. The high-KCl (50 mM)-stimulated release of DA decreased in the oocytes injected with rat brain mRNA together with antibody to synaptophysin. 5. Immunoblot analysis demonstrated that synaptophysin was expressed in the brain mRNA-injected oocytes but not in the noninjected and water-injected oocytes. 6. Thus, uptake and release machinery similar to native dopaminergic nerve terminals was expressed in Xenopus oocytes by injecting mRNA-extracted from the rat brain, and synaptophysin may play a role in the exocytotic release of DA.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2002

Increased synaptophysin expression through whisker stimulation in rat.

1. Synaptophysin is responsible for the cycling of the synaptic vesicles containing the neurotransmitter, and it can be phosphorylated. 2. This study examined whether repeated whisker stimulation alters the expression of synaptophysin mRNA in the rat barrel cortex, and found induced expression of synaptophysin mRNA in the contralateral barrel cortex compared to that in the ipsilateral hemi sphere. 3. This result suggests that synaptophysin is involved in the modulation of the synaptic plasticity.

Afferent Pathways↗
PubMed2005

Tyrosine phosphorylation of synaptophysin in synaptic vesicle recycling.

The integral SV (synaptic vesicle) protein synaptophysin was one of the first nerve terminal proteins identified. However its role, if any, in the SV life cycle remains undetermined. One of the most prominent features of synaptophysin is that its cytoplasmic C-terminus largely consists of pentapeptide repeats initiated by a tyrosine residue. Synaptophysin is heavily phosphorylated by tyrosine kinases in the nerve terminal, suggesting that this phosphorylation is central to its function. This review will cover the evidence for tyrosine phosphorylation of synaptophysin and how this phosphorylation may control its function in the SV life cycle.

Amino Acid Sequence↗
PubMed1994

Differences in the distribution of cytochrome b561 and synaptophysin in dog splenic nerve: a biochemical and immunocytochemical study.

Compared with neurons of the CNS, the organization of the peripheral adrenergic axon and nerve terminal is more complex because two types of neurotransmitter-containing vesicles, i.e., large (LDVs) and small dense-core vesicles, coexist with the axonal reticulum (AR) and the well-characterized small synaptic vesicles. The AR, which is still poorly examined, is assumed to play some role in neurosecretion. We have studied the subcellular localization of noradrenaline, cytochrome b561, and synaptophysin in control and ligated dog splenic nerve using both biochemical and ultrastructural approaches. Noradrenaline and cytochrome b561 coaccumulated proximal to a ligation, whereas distally only the latter was found. Despite a codistribution with noradrenaline at high densities in sucrose gradients, synaptophysin did not accumulate on either side of the ligation. At the ultrastructural level, cytochrome b561 immunoreactivity was found on LDVs and AR elements, both accumulating proximal to the ligation. Distally, the multivesicular bodies (MVBs), immunolabeled for cytochrome b561, account for the retrograde transport of LDVs and AR membranes retrieved at the nerve terminal. No synaptophysin immunoreactivity could be detected on LDVs, AR, or MVBs. The results obtained from the ligation experiments together with the ultrastructural data clearly illustrate that synaptophysin is absent from LDVs and AR elements in adrenergic axons.

Animals↗
PubMed2003

Cellugyrin and synaptogyrin facilitate targeting of synaptophysin to a ubiquitous synaptic vesicle-sized compartment in PC12 cells.

Cellugyrin represents a ubiquitously expressed four-transmembrane domain protein that is closely related to synaptic vesicle protein synaptogyrin and, more remotely, to synaptophysin. We report here that, in PC12 cells, cellugyrin is localized in synaptic-like microvesicles (SLMVs), along with synaptogyrin and synaptophysin. Upon overexpression of synaptophysin in PC12 cells, it is localized in rapidly sedimenting membranes and practically is not delivered to the SLMVs. On the contrary, the efficiency of the SLMV targeting of exogenously expressed cellugyrin and synaptogyrin is high. Moreover, expression of cellugyrin (or synaptogyrin) in PC12 cells dramatically and specifically increases SLMV targeting of endogenous synaptophysin. Finally, we utilized the SLMV purification scheme on a series of non-neuroendocrine cell types including the mouse fibroblast cell line 3T3-L1, the Chinese hamster ovary cell line CHO-K1, and the monkey kidney epithelial cell line COS7 and found that a cellugyrin-positive microvesicular compartment was present in all cell types tested. We suggest that synaptic vesicles have evolved from cellugyrin-positive ubiquitous microvesicles and that neuroendocrine SLMVs represent a step along that pathway of evolution.

3T3-L1 Cells↗
PubMed2003

Neuroendocrine tissue-specific transcription factor, BETA2/NeuroD, in gastric carcinomas: a comparison with chromogranin A and synaptophysin expressions.

BETA2/NeuroD (NeuroD) is a basic helix-loop-helix type of transcription factor mainly involved in neuroendocrine differentiation. In this study, we evaluated the prevalence of neuroendocrine differentiation in gastric carcinomas by analyzing the NeuroD expression in comparison with those of chromogranin A and synaptophysin. Of the 70 cases of gastric adenocarcinoma, the expressions of NeuroD, chromogranin A, and synaptophysin were detected in 17 (24.3%), four (5.7%), and 24 cases (34.3%), respectively, with preferential expressions in a non-solid type of poorly differentiated adenocarcinoma. The expression pattern of NeuroD was mostly concordant with that of synaptophysin and partly with chromogranin A, indicating that NeuroD serves as a good neuroendocrine marker in gastric adenocarcinomas. On the other hand, no immunoreactivity against NeuroD was detectable in nine cases of gastric neuroendocrine carcinomas, including small cell carcinomas, despite the presence of synaptophysin and chromogranin A expressions. These findings led us to conclude that neuroendocrine differentiation is estimated to be present in 20-30% of gastric adenocarcinomas with preference to a non-solid type of poorly differentiated adenocarcinoma. In addition, the negative expression of NeuroD in neuroendocrine carcinomas suggests that other regulatory mechanisms are possibly involved in the development of neuroendocrine carcinoma.

Adenocarcinoma↗
PubMed1993

The synaptic vesicle proteins SV2, synaptotagmin and synaptophysin are sorted to separate cellular compartments in CHO fibroblasts.

We expressed the synaptic vesicle proteins SV2, synaptotagmin, and synaptophysin in CHO fibroblasts to investigate the targeting information contained by each protein. All three proteins entered different cellular compartments. Synaptotagmin was found on the plasma membrane. Both SV2 and synaptophysin were sorted to small intracellular vesicles, but synaptophysin colocalized with early endosomal markers, while SV2 did not. SV2-containing vesicles did not have the same sedimentation characteristics as authentic synaptic vesicles, even though transfected SV2 was sorted from endosomal markers. We also created cell lines expressing both SV2 and synaptotagmin, both synaptotagmin and synaptophysin, and lines expressing all three synaptic vesicle proteins. In all cases, the proteins maintained their distinct compartmentalizations, were not found in the same organelle, and did not created synaptic vesicle-like structures. These results have important implications for models of synaptic vesicle biogenesis.

Animals↗