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At least 1,045 records · Page 58Linked to original sources
PubMed1999

Target-specific factors regulate the formation of glutamatergic transmitter release sites in cultured neocortical neurons.

Synapse formation in the mammalian CNS is thought to involve specific target recognition processes between presynaptic and postsynaptic neurons leading to the establishment of defined neuronal circuits. To study the role of target neuron-specific factors in synaptogenesis, we used cocultures of presynaptic explants and dissociated target neurons from rat neocortex, which enabled us to selectively vary the postsynaptic target neurons. Cocultures containing target neurons that were obtained early during development [embryonic day 16 (E16)] were compared to cocultures containing target neurons that were obtained at a later embryonic stage (E19). Postsynaptic currents (PSCs) were evoked in target neurons by maximal extracellular stimulation in the presynaptic explant. The mean amplitudes of AMPA and NMDA receptor-mediated PSCs were sixfold reduced in E16 target neurons, whereas the mean amplitudes of GABA(A) receptor-mediated PSCs did not differ between E16 and E19 target neurons. This reduction was in part caused by an apparently twofold reduction in mean quantal amplitude, as shown by recording AMPA receptor-mediated miniature PSCs. In addition, a reduced number of glutamatergic release sites in E16 target neurons was revealed by synapsin I immunostaining of dendritic presynaptic terminals. No differences in mean release probability were observed between E16 and E19 target neurons. Thus, the formation of glutamatergic transmitter release sites was strongly influenced by target neuron-specific factors. The formation of functional GABAergic synapses, however, was independent of the type of target neurons, suggesting specific retrograde signaling during the establishment of glutamatergic synapses.

Animals↗
PubMed1999

The establishment of GABAergic and glutamatergic synapses on CA1 pyramidal neurons is sequential and correlates with the development of the apical dendrite.

We have performed a morphofunctional analysis of CA1 pyramidal neurons at birth to examine the sequence of formation of GABAergic and glutamatergic postsynaptic currents (PSCs) and to determine their relation to the dendritic arborization of pyramidal neurons. We report that at birth pyramidal neurons are heterogeneous. Three stages of development can be identified: (1) the majority of the neurons (80%) have small somata, an anlage of apical dendrite, and neither spontaneous nor evoked PSCs; (2) 10% of the neurons have a small apical dendrite restricted to the stratum radiatum and PSCs mediated only by GABA(A) receptors; and (3) 10% of the neurons have an apical dendrite that reaches the stratum lacunosum moleculare and PSCs mediated both by GABA(A) and glutamate receptors. These three groups of pyramidal neurons can be differentiated by their capacitance (C(m) = 17.9 +/- 0.8; 30.2 +/- 1.6; 43.2 +/- 3.0 pF, respectively). At birth, the synaptic markers synapsin-1 and synaptophysin labeling are present in dendritic layers but not in the stratum pyramidale, suggesting that GABAergic peridendritic synapses are established before perisomatic ones. The present observations demonstrate that GABAergic and glutamatergic synapses are established sequentially with GABAergic synapses being established first most likely on the apical dendrites of the principal neurons. We propose that different sets of conditions are required for the establishment of functional GABA and glutamate synapses, the latter necessitating more developed neurons that have apical dendrites that reach the lacunosum moleculare region.

Animals↗
PubMedDate not supplied

[Rasnmussen syndrome. 7 years' follow-up. Aspects related to cerebral plasticity in epilepsy].

Present study represents a case follow up for seven years. A case of Epilepsy Partialis Continua (EPC) in a fifteen year old girl was studied with CT, MRI, cerebral SPECT and constantly EEG procedures: The SPECT study showed in right frontal lobe and right temporal lobe hypoperfusion (reduction of regional cerebral blood flow [rCBF]) cerebral zone in the interictal period and hyperperfusion (increase rCBF) in the ictal period in the same hemisphere. The EEG showed abnormal activity consisting in sharp wave and polyphasic sharp wave in frontal and temporal regions. The medical treatment was refractory at all kind of anticonvulsant drugs. In order to improve the refractory epilepsy the team decided an epilepsy surgery with right temporal lobotomy and right frontal corticetomy. This procedure were done at the eight year old and the results were satisfactory immediately after the surgery with absolute control and normal cognitive performance two weeks later the surgery. This patient was follow up for seven years with EEG constantly with normal activity, SPECT and MRI, all studies showed functional hemispherectomy, total absence in the structure and cerebral blood flow in right hemisphere with normal perfusion and structure in left hemisphere. The late control of neuropsychology assessment showed some deficits in the I.Q. cognitive performance, evaluated by the Weschler scale and Machover tests. These findings would be able to demonstrate a phenomenon of brain plasticity and neuronal restoration in the left cerebral hemisphere after to remove the abnormal cerebral epilepsy focus. This procedure might permits the restoration of inadequate neuronal environment and normalization of neural physiological stability. The postulated mechanisms of reorganization of function are unmasking, nonsynaptic diffusion neurotransmission and receptor plasticity, trophic factors, synapsins and neurotransmitters. The neuropsychological mechanism to preserve the functions would be involving in a cortical reorganization with axonal and dendritic development beside sprouting and synaptogenesis. This patient is a good example of neuronal plasticity in epilepsy surgery.

Age Factors↗
PubMed2003

Selectively reduced expression of synaptic plasticity-related genes in amyloid precursor protein + presenilin-1 transgenic mice.

A critical question in Alzheimer's disease (AD) research is the cause of memory loss that leads to dementia. The amyloid precursor protein + presenilin-1 (APP+PS1) transgenic mouse is a model for amyloid deposition, and like AD, the mice develop memory deficits as amyloid deposits accumulate. We profiled gene expression in these transgenic mice by microarray and quantitative RT-PCR (qRT-PCR). At the age when these animals developed cognitive dysfunction, they had reduced mRNA expression of several genes essential for long-term potentiation and memory formation (Arc, Zif268, NR2B, GluR1, Homer-1a, Nur77/TR3). These changes appeared to be related to amyloid deposition, because mRNA expression was unchanged in the regions that did not accumulate amyloid. Transgene expression was similar in both amyloid-containing and amyloid-free regions of the brain. Interestingly, these changes occurred without apparent changes in synaptic structure, because a number of presynaptic marker mRNAs (growth-associated protein-43, synapsin, synaptophysin, synaptopodin, synaptotagmin, syntaxin) remained stable. Additionally, a number of genes related to inflammation were elevated in transgenic mice, primarily in the regions containing amyloid. In AD cortical tissue, the same memory-associated genes were downregulated. However, all synaptic and neuronal transcripts were reduced, implying that the loss of neurons and synapses contributed to these changes. We conclude that reduced expression of selected genes associated with memory consolidation are linked to memory loss in both circumstances. This suggests that the memory loss in APP+PS1 transgenic mice may model the early memory dysfunction in AD before the degeneration of synapses and neurons.

Aged↗
PubMed2003

Synergistic effects of brain-derived neurotrophic factor and chondroitinase ABC on retinal fiber sprouting after denervation of the superior colliculus in adult rats.

Damage to the adult CNS often causes devastating and permanent deficits because of the limited capacity of the brain for anatomical reorganization. The finding that collateral sprouting of uninjured fiber tracts mediates recovery of function prompts the search for experimental strategies that stimulate axonal plasticity after CNS trauma. Here we characterize treatments that promote the sprouting of undamaged retinal afferents into the denervated superior colliculus (SC) after a partial retinal lesion in the adult rat. Delivery of brain-derived neurotrophic factor (BDNF) was performed to enhance the intrinsic potential of retinal ganglion cells to reelongate their axons. Reduction of the neurite growth-inhibitory properties of the adult SC was accomplished via treatment with chondroitinase ABC (C-ABC), which degrades chondroitin sulfate proteoglycans. Retinal axons were labeled via intraocular injections of fluorescently tagged cholera toxin B subunit, and fiber sprouting within the denervated SC was measured by quantitative laser-scanning confocal microscopy 1 week after the retinal lesion. We found that both the administration of BDNF and the injection of C-ABC induce significant sprouting of retinal afferents into the collicular scotoma. Remarkably, the combined treatment with BDNF and C-ABC showed synergistic effects on axon growth. Colocalization analysis with anti-synapsin antibodies demonstrated synapse formation by the sprouting axons. These results suggest that the combined treatment with BDNF and C-ABC can be relevant in therapies for the repair of the damaged adult CNS.

Animals↗
PubMed1992

Purification and characterization of a brain-specific multifunctional calmodulin-dependent protein kinase from rat cerebellum.

A brain-specific multifunctional calmodulin-dependent protein kinase, calmodulin-dependent protein kinase IV, which exhibited characteristic properties quite different from those of calmodulin-dependent protein kinase II, was purified approximately 230-fold from rat cerebellum. The purified preparation gave two protein bands with molecular weights of 63,000 (alpha) and 66,000 (beta) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, both of which showed protein kinase activity as examined by the activity gel method. The molecular weight of the enzyme was estimated as about 67,000 from sedimentation coefficient (3.2 S) and Stokes radius (50 A), indicating a monomeric structure of the enzyme. The enzyme phosphorylated smooth muscle myosin light chain, synapsin I, microtubule-associated protein 2, tau protein, myelin basic protein, histone H1, and tyrosine hydroxylase in a Ca2+/calmodulin dependent manner, suggesting that the enzyme is a multifunctional calmodulin-dependent protein kinase capable of phosphorylating a large number of substrates. A synthetic peptide, Lys-Ser-Asp-Gly-Gly-Val-Lys-Lys-Arg-Lys-Ser-Ser-Ser-Ser, was found to be a specific substrate for this kinase and, using this peptide as substrate, the distribution of the enzyme activity in various rat tissues was examined. The activity was found in cerebral cortex, brain stem, and cerebellum, most abundantly in cerebellum, but other tissues tested, including liver, spleen, kidney, lung, heart, skeletal muscle, and adrenal gland showed very little activity.

Animals↗
PubMed1992

Olfactory toxicity of beta,beta'-iminodipropionitrile in the rat.

Following a pilot study which revealed olfactory epithelial degeneration induced by beta,beta'-iminodipropionitrile (IDPN), dose-response and time-course analyses were undertaken to further characterize the effects of IDPN on the olfactory system. Male rats were sacrificed at multiple time points ranging from 24 hr after a single dose to 56 days after three consecutive daily doses of IDPN (0-400 mg/kg i.p.). Nasal cavities were fixed, decalcified and embedded in paraffin; 5 microns sections were stained with hematoxylin and eosin, middle neurofilament protein antibody or olfactory marker protein antiserum. Olfactory bulbs were removed for slot blot analyses of glial fibrillary acidic protein, synapsin I and p38. Another group of rats was treated with saline or IDPN and perfused 6 hr or 1, 2, 3, 7, 14 or 28 days after the last dose. Olfactory bulb axonal degeneration was visualized using a modified Gallyas technique. Twenty-four hours after treatment with 200 or 400 mg/kg IDPN, there was severe, highly site-specific mucosal degeneration in the dorsal-medial nasal cavity; regeneration was incomplete 8 weeks later. IDPN increased olfactory bulb glial fibrillary acidic protein, peaking 7 days after three daily 400 mg/kg doses, and remaining significantly elevated 8 weeks after treatment. Olfactory bulbs contained substantial silver deposition in afferent axon bundles in the glomerular layer, beginning 24 hr after the first dose and persisting for 14 days after dosing. Although only a portion of the olfactory epithelium was damaged by IDPN, all axon bundles entering the olfactory bulb were involved, suggesting the lack of a clear topographic arrangement of sensory endings in the olfactory bulb.

Animals↗
PubMed2003

[Probing of the target molecules of Rho-kinase and its function in neuronal cells].

Genome project terminated and post-genome project started, one of which aim is to understand the function and its regulation mechanism(s) of the molecules in living cells. Protein phosphorylation is one of the most common reactions responsive to extracellular stimulants. It is well understood about the involvement of Rho/Rho-kinase and Cdc42/p21-activated kinase (PAK) in the functions of muscle and non-muscle cells, but in neuronal cells little or poorly is understood. This is due to poor evidences about the target molecules of Rho-kinase and PAK and its functions in neuronal cells. We have revealed using a phosphorylation site-specific antibody that PAK targets synapsin Ia at Ser603 in vitro and in neuronal cells in culture, which is recognized as CaMKII site. This is reasonable, because the 600RQAS603 around Ser603 is also consensus motif for the phosphorylation of PAK and Rho-kinase besides CaMKII. Like this, we have tried to define the target molecules of Rho-kinase in neuronal cells. In this symposium, I would present that both Rho-kinase and PAK target MARCKS at Ser159 in vitro and in neuronal cells stimulated with LPA and bradykinin, respectively. Moreover, we would address the role of phosphorylation of MARCKS at Ser159 in neuronal functions.

Animals↗
PubMed2005

[The functional change in the 5-HT1A receptor induced by stress and the role of the 5-HT1A receptor in neuroprotection].

Mice exposed to various stresses, especially restrained-stress, revealed the anxiogenic effect detected by the light-dark test. Under this condition, a remarkable decrease in [35S]GTPgammaS binding to membranes from the prefrontal cortex, amygdala and hypothalamus of restrained-stress mice stimulated by the selective 5-HT1A receptor agonist 5-carboxamidotriptamine (5-CT) was clearly observed, whereas a significant increase in [35S]GTPgammaS binding stimulated by the 5-HT1A receptor agonist was clearly observed in the dorsal raphe nuclei (DRN) of restrained-stress mice. The immunohistochemical study showed a drastic reduction in phosphorylated-CREB-like immunoreactivity in the DRN of restrained-stress mice. Furthermore, we found a drastic reduction in myelin-associated glycoprotein (MAG)-like immunoreactivity (MAG-IR) in the DRN, amygdala and hypothalamus, indicating the direct suppression of synaptic transmission in these regions. It has been accepted that GSK3beta in the Wnt signal pathway plays an important role in various neuronal functions including apoptosis, clustering of synapsin I and early growth and axonal remodeling. In the present study, the increase in protein levels of GSK3beta and phosphorylated-GSK3beta to cytosol fractions of the amygdala was noted in restrained-stress mice. Taken together, these results suggest that restrained stress may directly affect the 5-HT1A receptor-regulated synaptic transmission in the brain, leading to the expression of the anxiogenic effect in mice. It is well known that various stresses induce intracellular oxidative stress. The present study was then undertaken to investigate the effect of the stimulation of 5-HT1A receptors on oxidative stress. Treatment with H2O2 caused the activation of caspase-3-positive cells and the reduction in levels of MAG-IR in the limbic neuron/glia cocultures as compared to medium alone. The stimulation of 5-HT1A receptor by 5-CT produced a dramatic protection against H2O2-triggered activation of caspase-3 and reduction in levels of MAG-IR. These results suggest that 5-HT1A receptors were involved in the modulation of anxiety and the understanding of molecular mechanisms of 5-HT1A receptor-related cascades may pave the way for new therapeutic strategies for affective disorders.

Amygdala↗
PubMed1991

Active catalytic fragment of Ca2+/calmodulin-dependent protein kinase II. Purification, characterization, and structural analysis.

We report the purification and characterization of an active catalytic fragment of Ca2+/calmodulin-dependent protein kinase II, derived from autophosphorylation and subsequent limited chymotryptic digestion of the purified rat forebrain soluble kinase. The purified fragment was completely Ca2+/calmodulin-independent, existed as a monomer, and phosphorylated synapsin I at the same sites as does the native form of Ca2+/calmodulin-dependent protein kinase II. Kinetic studies with the purified fragment revealed a more than 10-fold increase in Vmax and a 50% decrease in Km for synthetic peptide substrates, compared with native Ca2+/calmodulin-dependent protein kinase II. No 32P-labeled autophosphorylated residues were detected in the purified active fragment, indicating that the autophosphorylation sites were not contained within this fragment. Comparative studies of this active fragment (30 kDa) and its inactive counterpart (32-kDa fragment) revealed certain structural details of both fragments. Calmodulin-overlay study, immunoblot analysis, and direct amino acid sequencing suggest that both fragments contain the entire NH2-terminal catalytic domain and were generated by distinct cleavage within the regulatory domain. The putative cleavage sites for both fragments are discussed.

Amino Acid Sequence↗
PubMed1991

The major 35S-methionine-labeled rapidly transported protein (superprotein) is identical to SNAP-25, a protein of synaptic terminals.

Superprotein is a rapidly axonally transported protein that is conspicuously labeled with 35S-methionine supplied to the cell bodies of retinal ganglion cells. Superprotein candidates are apparent among the rapidly transported proteins of many neurons from the CNS and PNS, including cranial, sympathetic, sensory, and motor neurons from mammals, fish, and amphibians. To determine the identity of Superprotein, we purified it from rabbit visual system and spinal cord and determined the amino acid sequence of seven of its tryptic peptides. The sequence shows that Superprotein is SNAP-25, a protein recently predicted from a cDNA sequence; SNAP-25 has been reported to be concentrated in the synaptic terminals of a selected population of CNS neurons. We measured the amount of radioactivity associated with Superprotein in tissue containing axons (optic tract) and synaptic terminals (superior collicules) of rabbit retinal ganglion cells. Labeled Superprotein disappeared from the superior colliculus more rapidly than another protein (synapsin I-like protein) that is concentrated in synaptic terminals. These results serve to unite the observations on the synthesis, distribution, metabolism, and axonal transport of Superprotein with observations of SNAP-25 and its mRNA.

Animals↗
PubMed1990

Nerve growth factor-induced differentiation of human neuroblastoma and neuroepithelioma cell lines.

A series of neuroepithelioma and neuroblastoma cell lines were screened for nerve growth factor (NGF)-induced differentiation. All three neuroepithelioma cell lines and all nine neuroblastoma cell lines with amplified N-myc oncogene did not show any apparent NGF-induced differentiation. However, neurite extension was observed for three of six neuroblastoma cell lines with single-copy N-myc oncogene. The three responsive lines had a neuronal phenotype (short processes) which was enhanced by the addition of NGF. The three nonresponsive cell lines were flat without any processes. The addition of NGF to the responsive cell lines resulted in an up-regulation of neurofilament mRNA expression. Peripherin and synapsin, two markers of terminal neuronal differentiation, were not induced. There was little effect of NGF on the rate of cell growth or colony formation on soft agar. Binding of NGF to eight of the cell lines was analyzed by the method of Scatchard. Two responsive neuroblastoma cell lines and one nonresponsive neuroepithelioma cell line expressed both low- and high-affinity binding sites. Two nonresponsive neuroblastoma cell lines expressed only a small number of high-affinity binding sites, and two other nonresponsive neuroblastoma cell lines did not detectably bind NGF. Hence, NGF-induced differentiation is confined to a particular class of neural-related tumors, and, even for these cell lines, differentiation is incomplete.

Cell Differentiation↗
PubMed1991

Detailed genetic mapping of the A-raf proto-oncogene on the mouse X chromosome.

The transcribed murine A-raf proto-oncogene has been localized to the proximal region of the mouse X chromosome, within the context of four other active genes in this region which together constitute a conserved linkage group between mouse and man. This localization has been accomplished using species-specific restriction fragment length variation and DNAs from a previously defined informative subset of progeny representative of a set of 100 progeny from an interspecific backcross between inbred C57BL/6JRos and wild-derived Mus spretus. This new data regionally orders the mouse A-raf locus relative to the 24 X-linked markers previously examined in this backcross. We find that A-raf co-localizes with two other active genes, tissue inhibitor of metalloproteinases (Timp) and synapsin (Syn-1), 4.0 +/- 2.0 cM distal to the Otc gene at the proximal end of the mouse X chromosome, for a partial gene order in this region of: centromere-Cybb-Otc-Timp/A-raf/Syn-1-Xlr-1-Hprt.

Animals↗
PubMed1989

Ca2+/calmodulin-dependent protein kinase enriched in cerebellar granule cells. Identification of a novel neuronal calmodulin-dependent protein kinase.

Ca2+-sensitive protein kinases are thought to play a pivotal role in Ca2+-mediated neuronal communication. We describe here the cloning, purification, and characterization of a major Ca2+/calmodulin-dependent, brain-specific protein kinase which is particularly enriched in cerebellar granule cells. The enzyme is comprised of Mr 65,000 and 67,000 polypeptides which copurify to homogeneity and phosphorylate synapsin I. The protein kinase is coded for by two poly(A+) RNAs of 2.0 and 3.5 kilobases which probably derive from a single gene. Two cDNA inserts, one of 198 base pairs and one of 1225 base pairs, contain a total of 677 base pairs of the protein coding sequence which includes sequences homologous to other calmodulin-dependent protein kinases including part of the calmodulin-binding domain. The surprising presence of extended sequences which are enriched in glutamate residues may influence the subcellular distribution of this kinase. Immunohistochemical localization with an affinity-purified antibody reveals that whereas the enzyme is expressed in several neuronal subpopulations, it is exceptionally enriched in the granule cells of the cerebellum. The relevance of the biochemical, molecular, and histologic properties of this enzyme is discussed in the context of neuronal Ca2+ signaling.

Amino Acid Sequence↗
PubMed1989

In situ protein phosphorylation in hippocampal tissue slices.

We have studied the subcellular distribution of phosphoproteins in intact hippocampal slices and examined factors that regulate their phosphorylation and dephosphorylation in situ. The presence of Ca2+ in slice equilibration and prelabeling buffers and high-K+-induced depolarization markedly increased 32Pi incorporation into endogenous proteins. Ca2+-stimulatory effects were significantly reduced by Ca2+-channel blockers and the calmodulin antagonist W-13. Certain proteins were dephosphorylated in situ, and their dephosphorylation was dependent on both Ca2+ and depolarization. A number of proteins phosphorylated in situ was similar to those previously characterized in synaptic fractions phosphorylated in vitro. Many phosphoproteins were identified on the basis of molecular weight, isoelectric point, immunoreactivity, and phosphopeptide mapping; these included the 87 kDa substrate of protein kinase C, synapsin I, the 50 and 60 kDa subunits of Ca2+/calmodulin-dependent protein kinase II (CKII), tubulin, B-50, the alpha-subunit of pyruvate dehydrogenase and myelin basic proteins. CKII phosphorylation in situ appeared similar but not identical to its in vitro counterpart. Phosphopeptide mapping analysis of in situ labeled substrate proteins indicated that cAMP-, Ca2+/calmodulin-, and Ca2+/phospholipid-dependent protein kinases were all active in slice preparations under basal conditions. Increased 32Pi labeling of hippocampal proteins following tissue depolarization appeared to be associated with increased activity of endogenous protein kinases since depolarization did not result in 32Pi-labeling of any new phosphoproteins.

Animals↗
PubMed1989

Identification of a novel proline-directed serine/threonine protein kinase in rat pheochromocytoma.

During investigations of the regulation of tyrosine hydroxylase (TH) by protein phosphorylation, a novel protein kinase activity has been discovered in rat pheochromocytoma. Originally detected as a trace contaminant in preparations of highly purified TH, this novel kinase activity phosphorylated TH at serine 8 in the proline-rich amino-terminal region of the enzyme. This particular site is not phosphorylated by, nor is the amino acid sequence surrounding this site selective for, any of the classical (i.e. well characterized) protein kinases. In this report, we describe the identification, characterization, and partial purification of this novel protein kinase. By utilizing a synthetic peptide corresponding to the amino-terminal region of TH, a selective assay for this protein kinase was developed. The kinase activity utilized ATP and magnesium, although GTP could also be utilized as a phosphate donor. The kinase activity was found to co-purify with TH activity through ammonium sulfate precipitation and DEAE-cellulose chromatography and could be only partially resolved from TH by heparin-agarose affinity chromatography. Substantial kinase activity could be resolved from TH by phosphocellulose chromatography. The novel kinase migrates as a protein with a molecular mass of approximately 45 kDa on gel permeation chromatography as well as sucrose density gradient centrifugation. Studies of site specificity indicate that this Ser/Thr kinase activity appears to be directed by an adjacent (carboxyl-terminal) proline residue, exhibiting a minimal recognition sequence of -X-Ser/Thr-Pro-X-. In addition to TH, this proline-directed protein kinase will also phosphorylate synapsin I, histone H1, and glycogen synthase, suggesting that this kinase may have multiple substrates in vivo. Additional findings indicate that the activity of proline-directed protein kinase is increased transiently in PC12 pheochromocytoma cells following treatment with nerve growth factor. Distinctions between this novel kinase and other well characterized protein kinases can be made on the basis of phosphorylation site specificity, chromatographic behavior, and physical characteristics.

Adrenal Gland Neoplasms↗
PubMed1989

Development of inhibitory synapses among striatal neurons in vitro.

The development of excitatory and inhibitory synaptic connections has been studied in postnatal neurons from the caudate and putamen maintained in tissue culture. Excitatory postsynaptic potentials which were sensitive to the glutamate antagonist CNQX (6-cyano-7-nitroquinoxaline-2,3-dione) appeared between 4 and 8 d in vitro. This is the first indication that glutamatergic excitatory neurons may be intrinsic to the striatum. Spontaneous inhibitory postsynaptic currents appeared at approximately the same time, several days after process outgrowth. Antibodies to glutamic acid decarboxylase (GAD), the synthetic enzyme for GABA, labeled neurons which produce bicuculline-sensitive, inhibitory postsynaptic currents. GAD immunoreactivity and immunoreactivity to synapsin I, a synaptic vesicle-associated protein, became localized to discrete sites along neurites 4-8 d after plating. It is concluded that the punctate GAD immunoreactivity identified possible sites of presynaptic transmitter release.

Acetylcholinesterase↗
PubMed1989

Effect of tityustoxin and ouabain on protein phosphorylation in a crude synaptosome fraction.

1. The effect of tityustoxin (TsTX) and ouabain on the incorporation of 32P into a protein of the same apparent molecular weight as synapsin I is described. 2. Tityustoxin-stimulated protein phosphorylation in a crude synaptosome fraction increased up to a concentration of 3.0 microM at an incubation time of 15 s. 3. Trifluoperazine (100 microM) inhibited, while trifluoperazine sulphoxide (100 microM) did not alter the effect on the protein phosphorylation induced by tityustoxin. 4. Unlike tityustoxin, ouabain (100 microM) had no effect on protein phosphorylation even after incubation up to 20 min. 5. Ouabain at 10 microM, a concentration having no effect on rates of respiration and ATP hydrolysis in brain cortical slices, also had no effect on protein phosphorylation.

Acetylcholine↗