bluuebunny/crossref_metadata_2025 huggingface dataset:
Release of [3H]gamma-aminobutyric acid from glial (Muller) cells of the rat retina: effects of K+, veratridine, and ethylenediamine
Authors: Sarthy PV
Published: March 2018

In several neural systems, glial cells appear to take up and release gamma-aminobutyric acid (GABA) upon depolarization. We have studied the release of [3H]GABA from Muller (glial) cells in the rat retina by a double isotope-labeling technique in which Muller cells are preloaded with 3H-GABA while a population of neurons is prelabeled with [14C]glycine. By autoradiography, we have confirmed that [3H]GABA is taken up by the radially oriented Muller cells, whereas [3H]glycine is accumulated by a subset of amacrine cells (neurons). Using the double- labeling procedure, we have examined the effects of two depolarizing agents, high K+ and veratridine, and the GABA mimetic, ethylenediamine, on transmitter release from glial cells and neurons simultaneously. We found the following. (1) Depolarization with 56 mM K+ released both [3H]GABA and [14C]glycine. About 70 to 80% of this release was blocked in Ca2+-free medium. (2) Veratridine (10 microM) also released both of the transmitters. This release was strongly inhibited by 100 nM tetrodotoxin or 1mM procaine. Under Ca2+-free conditions, less than 20% isotope release was observed. (3) Ethylenediamine released [3H]GABA readily, whereas little [14C]glycine release was observed. Removal of Ca2+ had no significant effect on transmitter release. Furthermore, in Na+-free medium ethylenediamine failed to induce [3H] GABA or [14C]glycine release. These results suggest that high K+ and veratridine release [3H]GABA from Muller cells by a Ca2+-dependent process. Ethylenediamine, on the other hand, appears to induce [3H]GABA release by a Ca2+-independent, carrier-mediated exchange mechanism.
Physostigmine prolongs the elementary event underlying decay of inhibitory postsynaptic currents in Aplysia
Authors: White RL , Gardner D
Published: March 2018

Inhibitory postsynaptic currents (IPSCs) recorded at cholinergic synapses between identified neurons of the buccal ganglia of Aplysia decay exponentially. IPSC decay has been ascribed to a receptor-channel- dependent kinetic process, rather than to changes in subsynaptic acetylcholine (ACh) concentration, but is prolonged by the anticholinesterase eserine. Our data are consistent with a direct effect of 1.6 X 10(-4) M eserine on an elementary channel process. IPSC decay remains single exponential during eserine prolongation, suggesting that eserine slows the kinetic process responsible for decay, rather than substituting an additional kinetic process. In either control sea water or eserine, noise spectra computed from currents induced by pressure ejection of ACh are fitted by the sum of two Lorentzians. The slow corner frequency f1 is reduced from 6.3 to 3.5 Hz by eserine, consistent with a direct eserine action on receptor- channel kinetics, whereas apparent single-channel conductance was unchanged. Both IPSCs and ACh noise recorded in the same cells were comparably slowed by eserine. In eserine, decay time constant tau agreed with noise f1; however, tau and f1 in control sea water differed by 31%. The discrepancy may be accounted for by invoking an additional component to the recorded noise spectra, perhaps produced by synaptically active choline. In addition to the direct effect on kinetics, prolonged exposure to eserine produces a slow extra component to the IPSC decay tail.
Intentional responses to kinesthetic stimuli in orofacial muscles: implications for the coordination of speech movements
Authors: Cole KJ , Abbs JH
Published: March 2018

Reaction times (RTs) from human orofacial muscles were obtained with labial displacement and auditory stimuli to evaluate the potential for contributions by these sensorimotor processes to speech movement coordination. Because speech requires both concurrent and sequential movements, intramovement (labial stimulus, labial response) and intermovement (labial stimulus, lingual response) RT minima were examined. Intramovement and intermovement RT minima were from 46 to 52 msec. Response-related reductions in background muscle activity were observed with latencies as short as 35 msec. These observations indicate a potentially important role for RT processes in the coordination of speech movements. These control processes would appear to be open-loop and predictive.
Identification and purification of glial growth factor
Authors: Lemke GE , Brockes JP
Published: March 2018

Cultured rat Schwann cells are stimulated to divide by a protein growth factor, present in extracts of bovine brain and pituitary, which we have named glial growth factor (GGF). Two lines of evidence indicate that GGF activity in both brain and pituitary resides in a protein of Mr = 31,000. (1) Four independently isolated monoclonal antibodies that immunoprecipitate the activity react with an antigen of this molecular weight in sodium dodecyl sulfate (SDS)-polyacrylamide gels. (2) After SDS-polyacrylamide gel electrophoresis of partially purified preparations, mitogenic activity on Schwann cells is recovered at this molecular weight. GGF has been purified approximately 10(5)-fold to apparent homogeneity from bovine pituitary anterior lobes by a combination of column chromatography steps and preparative SDS gel electrophoresis. Purified human platelet-derived growth factor, a molecule with properties similar to those of GGF, is inactive on Schwann cells and therefore appears to be distinct.
Differences in the cellular distributions of two microtubule-associated proteins, MAP1 and MAP2, in rat brain
Authors: Huber G , Matus A
Published: March 2018

The distribution of microtubule-associated proteins (MAPs) 1 and 2 in rat brain was studied using monoclonal antibodies. Immunochemical staining showed that both MAP1 and MAP2 are present only in neurons and both are highly concentrated in dendrites compared to axons. Otherwise, they differed in distribution in various ways. MAP1 was present at low levels in axons, whereas MAP2 was never detectable in axons with either of two different fixation methods used. In the cerebellum the two MAPs differed in relative concentration in various classes on neurons. Thus, anti-MAP1 staining was strong in Purkinje cells but very faint in granule cells, whereas anti-MAP2 staining was strong in both. There were also distributional differences within the same cell. Thus, in Purkinje cells, anti-MAP1 staining is strong in the cell body, initial axon segment and throughout the dendritic tree, but anti-MAP2 staining is present only in dendrites beyond the initial proximal portion. These results suggest that microtubules with different molecular compositions are present in the cerebellum where they are distributed differently between cells as well as within the same cell.
A minute fraction of Syrian golden hamster retinal ganglion cells project bilaterally
Authors: Hsiao K , Sachs GM , Schneider GE
Published: March 2018

Bilaterally projecting retinal ganglion cells (BPRGCs) in the adult Syrian golden hamster were identified through the use of two retrogradely transported neuronal labels, horseradish peroxidase and Nuclear Yellow, placed separately in each optic tract. The distribution and size of doubly labeled retinal ganglion cells were characterized and their numbers were determined. Strict criteria were used to exclude artifactual doubly labeled cells. This work revealed that: (a) BPRGCs comprise less than 0.01% of the entire retinal ganglion cell population, averaging 7.4 (SD = 3) cells per retina; (b) BPRGCs are found primarily in the upper, peripheral retina and not along the vertical meridian or in the temporal crescent; and (c) BPRGCs correspond in size to ordinary retinal ganglion cells in their immediate vicinity, thus providing no evidence that they comprise a separate population of cells. Electrophysiological collision experiments were also performed, with stimulating electrodes in the two brachia of the superior colliculi and a recording electrode in one optic nerve. A collision effect was not detected, thus supporting the anatomical findings of rare bilateral branching of optic nerve axons. The occurrence of BPRGCs may reflect occasional ambiguities in the cues that guide axons through the chiasm.
Bilateral branching contributes minimally to the enhanced ipsilateral projection in monocular Syrian golden hamsters
Authors: Hsiao K
Published: March 2018

Studies of the plasticity of retinal projections following neonatal eye ablations in rats and hamsters have demonstrated an enhanced ipsilateral projection which affects both the terminal fields and the number of ipsilaterally projecting cells. The enhancement has been attributed to an excess of bilateral branching by single optic nerve axons, but this claim was not supported by the present study. Double retrograde labels were used to quantify the ipsilateral enhancement and measure the extent of bilateral branching in hamsters with neonatal eye removals. In 19 normal Syrian golden hamster retinas the average number of bilaterally projecting retinal ganglion cells (BPRGCs) was 7.4 (SD = 3), and the average number of ipsilaterally projecting retinal ganglion cells (IPRGCs) was 1349 (SD = 478) (Hsiao, K., G. M. Sachs, and G. E. Schneider (1984) J. Neurosci. 4: 359–367). In nine retinas of hamsters with removal of one eye at birth, the average number of BPRGCs was 25.3 (SD = 9.2), and the average number of IPRGCs per retina was 2036 (SD = 414). Although the increase in BPRGCs is statistically significant, it accounted for only 2 to 3% of the 51% increase in the number of IPRGCs. Various possible mechanisms underlying the formation of the enhanced projection are enumerated, and it is concluded that the predominant mechanism is a reduction of cell death in the developing population of IPRGCs. The responses of IPRGCs and BPRGCs to early eye enucleations were also examined with respect to age at enucleation and cell size. No difference in size was found between IPRGCs and BPRGCs in monocular hamsters compared to normal hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)
Evidence for selective release of somatostatin-14 and somatostatin-28(1- 12) from rat hypothalamus
Authors: Bakhit C , Koda L , Benoit R , Morrison JH , Bloom FE
Published: March 2018

Cysteamine administration to rats results in a marked depletion of hypothalamic somatostatin-14 (SS14) and a decrease of the potassium- evoked in vitro release of SS14 without a significant change in the content or release of somatostatin-28(1–12)-like immunoreactivity (SS28(1–12)-L1). Furthermore, cysteamine enhances the spontaneous release and markedly potentiates the potassium-evoked release of SS14 in the in vitro slice preparation. However, in vitro-administered cysteamine does not alter the spontaneous or potassium-evoked release of SS28(1–12)-LI. Immunohistochemical visualization of hypothalamic neuronal cell bodies and fibers following cysteamine administration shows a disappearance of the SS14 immunoreactive fibers and cell bodies with no apparent change in the SS28(1–12) immunoreactive fibers and cell bodies. These data suggest that, in rat hypothalamus, selective release of SS14 and SS28(1–12) can occur. The results are discussed in relation to possible sites of storage and release of the somatostatin- related peptides from synaptic nerve terminals.
Isolation and characterization of two myoactive neuropeptides: further evidence of an invertebrate peptide family
Authors: O'Shea M , Witten J , Schaffer M
Published: March 2018

The neuropeptide proctolin acts as a neuromuscular co-transmitter in insect skeletal muscle. As a prelude to determining whether other peptides may function in a similar way, we are attempting to isolate and characterize the chemical nature of new myoactive neuropeptides in insects. We examined the corpus cardiacum, a major insect neurosecretory structure of the American cockroach (Periplaneta americana), using a skeletal muscle bioassay and high pressure liquid chromatography fractionation and identified two myoactive factors, MI and MII. They are synthesized in the corpus cardiacum and released from it into the blood by a calcium-dependent mechanism. Amino acid and fast atom bombardment-mass spectroscopy analysis show that MI and MII are structurally related octapeptides representing the major secreted products of the cockroach corpus cardiacum. Both MI and MII are also present in the CNS and in the gut, indicating transmitter as well as hormonal functions in the cockroach. A survey in other species indicates MI may be present in invertebrates other than insects, but neither was found in the rat. The MI and MII peptides have clear chemical affinities to two previously described invertebrate peptides, locust adipokinetic hormone and crustacean red pigment concentrating hormone, as well as sharing biological activity with these peptides. Our results provide further evidence for the existence of a large family of structurally related peptides with divergent functions in a variety of invertebrate types.
Aluminum effect on slow axonal transport: a novel impairment of neurofilament transport
Authors: Bizzi A , Crane RC , Autilio-Gambetti L , Gambetti P
Published: March 2018

Administration of aluminum (Al) produces accumulation of neurofilaments (NF), called neurofibrillary tangles (NFT), in neuronal cell bodies and proximal axonal segments. This study was undertaken to investigate whether these changes are associated with impairment of the slow axonal transport. Local administration of AlCl3 induced the formation of NFT in 90 to 100% of the rabbit hypoglossal neurons. [35S]Methionine was then administered to the hypoglossal nerve nuclei. The hypoglossal nerves were processed 18 or 28 days later for one- and two-dimensional SDS-polyacrylamide gel electrophoresis and fluorography. Labeled NF polypeptides and a polypeptide of 57 kilodaltons (Kd) were not detectable beyond the proximal 9-mm segment of the hypoglossal nerve in Al-treated rabbits 18 days after labeling, whereas they were present up to 27 mm from the medulla in controls. Tubulin and polypeptides migrating with slow component b were not significantly affected. In rabbits sacrificed 28 days after labeling, accumulation of NF subunits within the proximal 9 mm of hypoglossal nerve was less dramatic, and labeled NF were present up to 30 mm from the medulla whereas they were detectable up to 45 mm in controls. Morphological studies demonstrated the presence of enlarged axons filled with NF in the proximal 9 mm of the hypoglossal nerve. In nerve segments immediately distal, axons were markedly reduced in size and contained no NF but an apparently normal number of microtubules and other organelles. Transport of NF and of a 57-Kd polypeptide is markedly but reversibly slowed down or blocked within the proximal 9-mm segments of the hypoglossal nerve following Al administration to the hypoglossal nucleus. It is suggested that NF transport is maintained distally, resulting in lack of NF in axonal segments immediately distal to the block. Local Al intoxication provides a novel model of impairment of NF transport.
Non-serotonergic origins of the dorsolateral funiculus in the rat ventral medulla
Authors: Johannessen JN , Watkins LR , Mayer DJ
Published: March 2018

Cells within the ventral medulla whose axons descend to the spinal dorsal horn via the dorsolateral funiculus (DLF) play an important role in pain modulation. Previous evidence suggests that this pathway is primarily serotonergic. We have examined this hypothesis directly using combined retrograde horseradish peroxidase/serotonin immunohistochemical staining. Cells of the ventral medulla contributing to the DLF were found to be largely non-serotonergic. This result was confirmed by two approaches: by the absence of a significant number of double-labeled cells following discrete horseradish peroxidase labeling of the DLF and by the persistence of double-labeled cells in animals with DLF lesions made rostral to intraspinal injections of horseradish peroxidase solutions. The conclusion is made that the previously described nucleus raphe magnus-DLF-dorsal horn pathway is predominantly non-serotonergic.
Physiological organization of layer 4 in macaque striate cortex
Authors: Blasdel GG , Fitzpatrick D
Published: March 2018

Numerous highly angled electrode penetrations through the opercular region of macaque striate cortex reveal that layers 4A, 4C alpha, and 4C beta--the primary input sublaminae for axons from the lateral geniculate nucleus (LGN)--are retinotopically organized on a fine scale and populated mostly by monocularly driven cells having small receptive fields and lacking orientation selectivity. Layer 4B, which does not receive a direct thalamic input, contains orientationally selective cells, and many of these are also direction selective. To a significant degree the response properties of cells in layers 4C alpha and 4C beta reflect the response properties of their respective afferent inputs, from the magno- and parvocellular laminae of the LGN. Accordingly, cells in layer 4C alpha have lower contrast thresholds and larger minimum response fields than do the cells in layer 4C beta. In contrast to this clear-cut separation, the cells of layer 4A (whose major source of direct LGN input arises from the parvocellular layers) exhibit both high and low contrast thresholds. With regard to the precision of retinotopic mapping that is seen in lamina 4C, it is noteworthy that there is substantial overlap among the minimum response fields of neighboring neurons. Due to a larger mean receptive field size, this overlap is greater in layer 4C alpha than it is in 4C beta. In either sublamina, however, the minimum cortical distance that separates different and nonoverlapping parts of the visual field corresponds closely--within a factor of 2--to the known arborizational spreads of single geniculate afferents.
Effects of amphetamine on intracellular responses of caudate neurons in the cat
Authors: Schneider JS , Levine MS , Hull CD , Buchwald NA
Published: March 2018

The effects of acute administration of amphetamine on membrane potentials and evoked postsynaptic potentials of caudate neurons in cats were assessed using intracellular recording. High doses of amphetamine (0.5 mg/kg, i.v.) produced a reversible depolarization of the cell membrane in 78% of cells tested. Low doses (0.1 mg/kg) had no effect on the resting membrane potential. Long-lasting increases in amplitude of both excitatory and inhibitory components of evoked postsynaptic potential sequences were observed after both high and low doses of amphetamine. These changes were more evident to cortical than to substantia nigra or to intralaminar thalamic stimulation. These results were shown to be independent of the peripheral autonomic actions of amphetamine. These effects appear to be mediated by the ability of amphetamine to alter catecholaminergic mechanisms in the caudate nucleus and suggest that increased dopamine release may have a facilitatory effect on both excitatory and inhibitory synaptic transmission.
Demonstration of in vivo synthesis of pro-opiomelanocortin-, beta- endorphin-, and alpha-melanotropin-like species in the adult rat brain
Authors: Liotta AS , Advis JP , Krause JE , McKelvy JF , Krieger DT
Published: March 2018

An in vivo labeling technique was utilized to demonstrate the in situ biosynthesis of pro-opiomelanocortin (POMC)-, beta-endorphin- and alpha- melanotropin (MSH)-like molecular species in rat brain. Unrestrained adult female rats were bilaterally cannulated in the hypothalamic arcuate nuclear region; [35S]methionine was infused either over a 15- min period with sacrifice 2 hr subsequently, or at a constant rate for 6 hr prior to sacrifice. Sequential immune-affinity chromatography and several chromatographic and electrophoretic techniques were employed to detect and characterize POMC-related material in the hypothalamic arcuate nuclear region, preoptic area, and median eminence. Four molecular species containing both corticotropin (ACTH) and beta- endorphin antigenic determinants within the same molecules were detected in the arcuate nuclear region and preoptic area. Two forms were similar to rat pituitary POMC with respect to apparent molecular weight (35,000 and 31,500) and [35S]methionine-containing tryptic fragments (one methionine each in N-terminal glycopeptide, ACTH, and beta-endorphin sequences of rat POMC). The other two forms (apparent Mr of 21,000 and 19,000) contained only the labeled tryptic fragments characteristic of ACTH and beta-endorphin. The detection of the latter forms suggests that POMC in brain, unlike its post-translational processing in rat pituitary, undergoes primary cleavage between the N- terminal peptide and the ACTH sequence. Peptides physicochemically indistinguishable from authentic beta-endorphin and des-acetyl alpha- MSH were detected in approximately equimolar amounts in all three brain regions. The ratio of POMC-like material to the alpha-MSH- and beta- endorphin-sized peptides was highest in the arcuate nuclear region, suggesting that POMC-like proteins are synthesized in the arcuate nuclear region and are processed into the smaller molecular species during axonal transport.
Cell determination and differentiation of identified serotonin- immunoreactive neurons in the grasshopper embryo
Authors: Taghert PH , Goodman CS
Published: March 2018

We have begun to investigate the factors that underlie neurotransmitter determination in the central nervous system of the grasshopper embryo. The most prominent serotonin-immunoreactive neurons in the segmental ganglia are three clonally related interneurons, cells S1, S2, and S3. S1 and S2 are sibling neurons and are the first two born in the family of neurons that is produced by neuroblast 7–3; cell S3 derives from one of the second-born pair in the same family. S1 is serotonin- immunoreactive in all thoracic and abdominal segments, S2 in all but two segments (T3 and A1), and S3 in only the prothorax (T1). These segment-specific differences are not due to differential cell death but rather can be ascribed to biochemical differences between lineally homologous neurons. Furthermore, these homologous neurons also display interesting segment-specific differences in their morphology. Laser ablation of neuroblast 7–3 before it begins its series of programmed cell divisions results in the absence of its normal serotonin- immunoreactive neuronal progeny when screened at mature stages. These experiments support the hypothesis that transmitter determination is at least in part regulated by cell lineage in the grasshopper embryo and that some clonally related neurons appear to share a common transmitter determination by virtue of their common lineage. The results further suggest that cell lineage regulation of transmitter determination may vary according to segment or may be modified by as yet unidentified segment-specific factors.
Evidence for 5-hydroxytryptamine, substance P, and thyrotropin- releasing hormone in neurons innervating the phrenic motor nucleus
Authors: Holtman JR , Norman WP , Skirboll L , Dretchen KL , Cuello C , Visser TJ , Hokfelt T , Gillis RA
Published: March 2018

Retrograde tracing with a fluorescent dye (Fast Blue) combined with immunohistochemistry was used to identify putative neurotransmitter(s) at the phrenic motor nucleus in the cat. Fast Blue was injected bilaterally into the diaphragm of five cats, where each phrenic nerve enters the muscle. Seven days later the animals were perfusion fixed and tissue sections from the fourth, fifth, and sixth cervical spinal cord segments were analyzed using a fluorescence microscope. Retrogradely labeled fluorescent phrenic motor neuron cell bodies appeared in all of the segments but primarily in sections from the fifth segment. The same or adjacent transverse sections were then used for the demonstration of the distribution of the neurotransmitters 5- hydroxytryptamine (5-HT), substance P, and thyrotropin-releasing hormone (TRH) in the area of the phrenic motor nucleus using the indirect immunofluorescence technique. The most conspicuous neurotransmitters found at the phrenic motor nucleus were 5-HT and substance P. We observed dense and diffuse fiber networks throughout the ventral horn which contains the phrenic motor nucleus. These fibers contained varicosities in close proximity to phrenic motor neurons. In addition to 5-HT- and substance P-containing nerve endings, some fibers containing TRH were also found in the area of the phrenic motor nucleus. These results are consistent with earlier physiological data suggesting that 5-HT, substance P, and TRH are important neurotransmitters and/or neuromodulators involved in central control of respiration.
The effects of monensin on transport of membrane components in the frog retinal photoreceptor. I. Light microscopic autoradiography and biochemical analysis
Authors: Matheke ML , Fliesler SJ , Basinger SF , Holtzman E
Published: March 2018

We have explored the use of the Na+-H+ ionophore monensin as a potential tool for the investigation of membrane assembly and transport in retinal photoreceptors. Autoradiographic analysis of frog retinas incubated with [3H]leucine in the presence of monensin revealed a lack of concentrated silver grains (“bands”) at the base of the rod outer segments, in contrast to controls. This is indicative of a pronounced monensin-induced decrease in disc membrane assembly. Biochemical analyses of whole retinas and isolated rod outer segment membranes showed that protein synthesis (including opsin synthesis) was not significantly inhibited under these conditions, whereas passage of membrane protein to the rod outer segment was blocked. Glycerolipid synthesis was not significantly affected by monensin. The results suggest that membrane proteins (e.g., opsin) destined for incorporation into the rod outer segment must pass through the Golgi apparatus and demonstrate the potential utility of monensin for inhibiting aspects of marcomolecule transport in photoreceptors.
[35S]-t-butylbicyclophosphorothionate binding sites are constituents of the gamma-aminobutyric acid benzodiazepine receptor complex
Authors: Supavilai P , Karobath M
Published: March 2018

t- Butylbicyclophosphorothionate ( TBPS ), a derivative of potent GABA antagonistic cage convulsants, has recently been introduced ( Squires , R. F., J.E. Casida , M. Richardson, and E. Saederup (1983) Mol. Pharmacol. 13:326–336) as ligand for a GABA-A receptor-linked drug receptor. Using conventionally prepared washed membrane fractions from rat cerebral cortex, we have confirmed that in the presence of 200 mM NaBr [35S] TBPS binds to a high affinity population of binding sites (Kd 26 +/- 5 nM) and that muscimol inhibits [35S] TBPS binding (IC50 0.32 microM) allosterically. In 200 mM NaCl the apparent affinity of [35S] TBPS binding sites is lower (Kd 60 +/- 5 nM), and muscimol has biphasic effects with stimulation at low concentrations of muscimol (EC50 0.023 microM) followed by inhibition at high concentrations (IC50 0.72 microM). Both base line [35S] TBPS binding (in 200 mM NaCl) and muscimol inhibition of [35S] TBPS binding (in 200 mM NaBr) are bidirectionally modulated by the occupancy of benzodiazepine receptors with its ligands. Benzodiazepine receptor agonists, regardless of their structure, enhance and inverse benzodiazepine receptor agonists inhibit base line [35S] TBPS binding and muscimol inhibition of [35S] TBPS binding. Fourteen ligands for benzodiazepine receptors display a similar in vitro profile as benzodiazepine receptor agonists or inverse benzodiazepine receptor agonists on [35S] TBPS binding as their anti- or proconvulsive effects in vivo suggest (Jensen, L. H., E. N. Petersen, and C. Braestrup (1983) Life Sci. 33: 393–399). That [35S] TBPS binding sites are constituents of a GABA benzodiazepine receptor complex is also suggested by a number of membrane pretreatments.(ABSTRACT TRUNCATED AT 250 WORDS)
Regulatory effect of dopamine on spatial properties of horizontal cells in carp retina
Authors: Teranishi T , Negishi K , Kato S
Published: March 2018

Three types of light-induced response (L-, RG-, and YRB -type S- potentials) recorded from isolated retinas of the carp (Cyprinus carpio) were identified by their spectral response and later by morphological localization of the recording sites marked with an intracellular Lucifer Yellow (LY). Horizontal cells in a given layer, generating one of the above response types, are electrically coupled via gap junctions, so that the injected LY normally diffused to several neighboring cells. The spatial property of the three types of responses was examined by enlarging the diameter of a light spot (0.25 to 4.0 mm) and displacing the spot (0.5 mm diameter) along a straight 4-mm line which passed over the recording point at the middle. In normal retinas, the half-decay distance of response amplitude with spot displacement was shorter in the order of L-, RG-, and YRB -type responses, and correspondingly the dye diffusion area was narrower in the same order of cells. Dopamine (DA; 10 to 20 microM), applied to the vitreous fluid beneath the isolated retina, altered the spatial property of all types of responses by increasing the amplitude of responses to central spots and decreasing that of those to distant spots, and it restricted the intracellular LY to single injected cells. In contrast, in retinas from which DA interplexiform cells had been deprived by prior destruction with a neurotoxin, 6-hydroxydopamine, the amplitude of responses became smaller while the half-decay distance was longer by 1.1- to 1.6-fold, depending upon the cell type, and the dye diffusion area in all types of cells became wider by 2-fold as compared to those in normal retinas.(ABSTRACT TRUNCATED AT 250 WORDS)
An effect of nerve growth factor on the parasympathetic ciliary ganglion
Authors: Collins F
Published: March 2018

Mouse submaxillary nerve growth factor (NGF) increases the length and density of neurites extended from embryonic chick ciliary ganglia in vitro. The effect is not as pronounced as with dorsal root ganglia, but it occurs at the same low concentrations of NGF. This effect was observed on polyornithine substrata with or without pretreatment of the substratum with conditioned medium. NGF did not significantly increase the length or density of neurites extended from spinal cord or neural retina explants in the same culture conditions. Stimulation of ciliary ganglion neurite outgrowth did not occur when NGF was replaced with cytochrome c or epidermal growth factor, whereas insulin had an effect comparable to that of NGF when present at much higher concentrations. Four different purified preparations of NGF gave identical results. The purity of two of these preparations was determined after radioiodination; greater than 98% of the radioactivity migrated as a single band on polyacrylamide gels, and greater than 94% of the radioactivity was bound by affinity purified anti-NGF antibody. The effect of NGF on neurite growth could be separated from its effect on neuronal survival. NGF failed to promote the survival of ciliary ganglion neurites even at concentrations 1000-fold higher than those which significantly stimulated neurite growth.(ABSTRACT TRUNCATED AT 250 WORDS)
Distribution, origin, and fine structures of cholecystokinin-8-like immunoreactive terminals in the nucleus ventromedialis hypothalami of the rat
Authors: Inagaki S , Shiotani Y , Yamano M , Shiosaka S , Takagi H , Tateishi K , Hashimura E , Hamaoka T , Tohyama M
Published: March 2018

The distribution, origin, and fine structures of cholecystokinin-8-like immunoreactive ( CCKI ) fibers in the nucleus ventromedialis hypothalami (vm) of the rat were examined using immunohistochemistry. CCKI fibers were moderately concentrated in the ventrolateral part of the vm, decreasing in number dorsomedially. However, no CCKI cells were seen in the vm even in colchicine-treated rats. In addition, the destruction of the lateral part of the nucleus parabrachialis dorsalis (pbd) where numerous CCKI cells were seen resulted in a marked decrease in CCKI fibers in the vm on the operated side. Electron microscopic observations revealed that CCKI terminals make synaptic contact with soma, spine, and the proximal segment of the dendrite. The neurons making synaptic contact with the CCKI fibers had moderately electron- lucent cytoplasm. These findings suggest that the CCKI fibers in the vm originate from CCKI cells in the lateral part of the pbd and directly influence the vm neurons.
Production of "ectopic" vasoactive intestinal peptide-like and neurotensin-like immunoreactivity in human pheochromocytoma cell cultures
Authors: Tischler AS , Lee YC , Perlman RL , Costopoulos D , Slayton VW , Bloom SR
Published: March 2018

Neoplastic chromaffin cells from human pheochromocytomas can exhibit extensive spontaneous and nerve growth factor (NGF)-induced outgrowth of neurite-like processes in vitro, despite the absence of such processes in vivo. To determine whether acquisition of neuron-like features by human pheochromocytoma cells in culture is accompanied by functional alterations, process outgrowth, vasoactive intestinal peptide-like immunoreactivity ( VIPLI ), neurotensin-like immunoreactivity (NTLI), and catecholamine content were studied in freshly dissociated cells and in 21-day-old cultures from six human pheochromocytomas. All of the cultures produced VIPLI and exhibited spontaneous process outgrowth. NGF stimulated process outgrowth and enhanced production of VIPLI . Dexamethasone inhibited process outgrowth and tended to decrease production of VIPLI . NTLI was detected in cells from only one of the tumors, and its production appeared to be regulated comparably to that of VIPLI . Catecholamine content decreased markedly in all of the cultures and was not regulated in parallel with either VIPLI or NTLI. The findings suggest that human pheochromocytoma cultures may help to elucidate cellular and molecular mechanisms regulating ectopic and normal VIP production.
Muscimol-scopolamine interactions in the rat brain: a study with 2- deoxy-D-[1-14C]glucose
Authors: Helen P , London ED
Published: March 2018

The 2-deoxy-D[1–14C]glucose method of Sokoloff was used to measure local cerebral glucose utilization (LCGU) in rats after injections of the GABA receptor agonist, muscimol (1.6 mg/kg and 4.0 mg/kg, i.v.); the muscarinic receptor antagonist, scopolamine (0.4 mg/kg and 2.0 mg/kg, i.v.); or combinations of both drugs. The aim was to identify brain regions where functional effects of GABAergic-cholinergic interactions could be seen. As noted previously, muscimol reduced LCGU in many brain regions. In contrast, scopolamine alone had no effect on LCGU in most brain regions; however, decreases were seen in the medial geniculate body, medial thalamic nucleus, and auditory and frontal cortical areas. Scopolamine increased LCGU in the cerebellar vermis and mesencephalic reticular formation. Although muscimol alone did not significantly affect LCGU in the external plexiform layer of the olfactory bulb or the anterior, periventricular, and parafascicular thalamic nuclei, rats treated with 0.4 mg/kg of scopolamine before 4.0 mg/kg of muscimol had LCGU decrements in those brain regions. Furthermore, the muscimol-induced decrease in LCGU in the medial cortex was enhanced by prior treatment with 0.4 mg/kg of scopolamine. In contrast, in certain brain regions where muscimol alone reduced LCGU (locus ceruleus; central gray matter; striatum; ventral, medial, reunients , and rhomboid thalamic nuclei; and the auditory cortex), scopolamine pretreatment antagonized these decrements. These findings suggest that endogenous cholinergic and GABAergic systems act antagonistically in some brain regions. However, in other brain regions, cholinergic transmission is required for full expression of GABAmimetic effects on LCGU.(ABSTRACT TRUNCATED AT 250 WORDS)
3,4-Dimethyl-2,5-hexanedione impairs the axonal transport of neurofilament proteins
Authors: Griffin JW , Anthony DC , Fahnestock KE , Hoffman PN , Graham DG
Published: March 2018

Accumulations of neurofilaments are observed in a variety of neurological disorders, and their pathogenesis is a fundamental problem of neuropathology. 2,5-Hexanedione (HD) neurotoxicity provides an extensively studied model of axonal neurofibrillary changes in which the pathogenetic mechanisms have been conjectural. Chronic exposure to HD results in neurofilament-filled swellings in the distal regions of large axons of exposed humans and experimental animals. In this report we describe the changes produced by a potent analogue of HD, 3,4- dimethyl-2,5-hexanedione ( DMHD ), in slow axonal transport in the rat sciatic motor axons. Young rats received 0.6 mmol/kg of DMHD for 5 days before [35S]methionine was injected into the lumbar ventral horns. Slow axonal transport of the neurofilament proteins, tubulin, and selected slow component b (SCb) proteins in DMHD -treated animals was compared to the profiles found in age-matched control animals. DMHD administration reduced the rate of transport of the neurofilament proteins 75 to 90%, while tubulin and the SCb proteins were only modestly retarded. No alterations in electrophoretic mobilities of slowly transported proteins were found, nor were any proteins accelerated in transport. These findings were systematically compared to the changes produced by administration of beta,beta'- immino - dipropionitrile (IDPN) (2.0 gm/kg, i.p.), an agent known to impair neurofilament transport. Although slightly less severe, the changes produced by DMHD were nearly identical to those of IDPN. In correlative morphological studies, the neurofilamentous changes were also comparable. The results indicate that DMHD and IDPN share the capacity to interfere selectively with neurofilament transport and thereby share pathogenetic mechanisms. DMHD provides a new agent for exploration of the organization and transport of the neuronal cytoskeleton.
In vivo and in vitro development of somatostatin-like-immunoreactivity in the peripheral nervous system of quail embryos
Authors: Garcia-Arraras JE , Chanconie M , Fontaine-Perus J
Published: March 2018

The appearance and development of somatostatin-like immunoreactivity (SLI) in the peripheral nervous system of quail embryos were studied using radioimmunoanalysis and immunocytochemistry. In vivo, no SLI is observed in neural crest cells before or during migration. SLI appears between days 3 and 4 of incubation in sympathetic ganglia, immediately following ganglion formation, and between days 4 and 5 of incubation in the adrenal gland, soon after the adrenal gland primordium first appears. The development of SLI in the adrenal gland differs from that in the sympathetic ganglia. While in the former the amount of SLI and the number of SLI-containing cells increase as the embryo ages, in the sympathetic ganglia the amount of SLI and the percentage of SLI- containing cells decrease. When migrating neural crest cells are obtained from the sclerotomal part of 3-day embryos and grown in culture, they first display SLI after 48 hr, and the amount of SLI increases thereafter. When the sympathoadrenal precursors are removed at 4 days of incubation and grown in vitro, SLI appears after 24 hr in culture and increases during the next few days. Our results demonstrate that SLI is present very early in the quail embryo and that its appearance parallels the differentiation of neural crest cells into autonomic sympathetic ganglionic cells. We also show that the differentiation of neural crest into SLI-containing cells can be reproduced in culture, thus permitting the study of peptide production and expression in vitro.
A single class of neurotensin receptors with high affinity in neuroblastoma X glioma NG108-15 hybrid cells that mediate facilitation of synaptic transmission
Authors: Nakagawa Y , Higashida H , Miki N
Published: March 2018

Receptor binding of [3H]neurotensin was examined on membrane preparations derived from neuroblastoma X glioma NG108–15 hybrid cells. The specific binding was saturable and reversible, and a dissociation constant (Kd) was calculated to be about 0.24 nM from the rate constants. Scatchard analysis of neurotensin binding at equilibrium revealed a single class of binding sites with a Kd of 0.86 nM and a maximal binding capacity (Bmax) of 250 fmol/mg of protein (7700 receptor sites/cell). [D-Arg9]-Neurotensin had a high affinity (IC50 = 0.5 nM) for the neurotensin receptors, but [D-Phe11]-neurotensin had a lower affinity (IC50 = 280 nM), while angiotensin II and bradykinin had almost no affinity for [3H]neurotensin-binding sites. Under similar conditions [3H]neurotensin binding to mouse and rat brain synaptosomal fractions showed two binding sites with high (0.86 and 0.44 nM) and low (13 and 19 nM) affinities. We have examined several possible physiological consequences of neurotensin receptor binding. Neurotensin (10 microM) exhibited no influence on adenylate cyclase activity, 45Ca uptake, or 32Pi incorporation into phosphatidylinositol fractions of NG108–15 cells. Electrophysiological study of isolated NG108–15 cells revealed neurotensin-induced transient hyperpolarization followed by sustained depolarization with enhanced membrane excitability. Application of neurotensin to NG108–15 cells that had formed synapses with cultured striated muscle cells caused a considerable increase in frequency of miniature endplate potentials from the muscle cells. These data show that NG108–15 cells possess a single class of neurotensin receptors similar to a high affinity site of synaptosomal membranes from the murine brains.(ABSTRACT TRUNCATED AT 250 WORDS)
The distribution and binding of zinc in the hippocampus
Authors: Sato SM , Frazier JM , Goldberg AM
Published: March 2018

Quantitative and qualitative studies suggest that zinc is concentrated in the mossy fiber boutons of the hippocampus and is believed to exist as a chelatable cytosolic pool. These studies were aimed at testing the hypothesis that a zinc-binding protein(s) or an amino acid pool in the cytosol is responsible for the sequestration of zinc. For comparison with the hippocampus, the cerebellum was chosen as a control region since it has been reported to contain lower levels of zinc both quantitatively and qualitatively. Initially, we confirmed that a quantitative difference in the levels of zinc exists between the hippocampus (12.59 +/- 0.85 micrograms of zinc/gm wet weight tissue, X +/- SD) and that this difference is reflected in cytosolic zinc levels. Using Ultrogel AcA 34 gel permeation chromatography, three major zinc- binding species were resolved. Two of these binding species appeared to account for most of the difference observed in the cytosolic levels of the two brain regions. Molecular weight criteria and differential pulse polarography behavior suggest that one of the species is a metallothionein-like protein. Based upon both molecular weight and ion exchange chromatography criteria, the other binding species may be a zinc-glutathione complex. There are no qualitative differences in the zinc-binding species localized in the cytosol of the hippocampus as compared with the cerebellum. However, the amount of binding species, in particular, the metallothionein-like protein and the putative zinc- glutathione complex, is greater in the hippocampus. These findings support the hypothesis that a cytosolic zinc-binding protein(s) may be responsible for the sequestration of zinc observed in the hippocampus.
Nerve growth factor-mediated enzyme induction in primary cultures of bovine adrenal chromaffin cells: specificity and level of regulation
Authors: Acheson AL , Naujoks K , Thoenen H
Published: March 2018

Primary cultures of bovine adrenal chromaffin cells provide large quantities of a homogeneous population of target cells for nerve growth factor (NGF) and, thus, are a suitable system for studying the molecular mechanism of action of NGF. In this study, we have shown that NGF mediates the specific induction of the key enzymes in catecholamine biosynthesis, tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT). Acetylcholinesterase (AChE), an enzyme which catalyzes the breakdown of acetylcholine, is also induced by NGF. We have compared NGF-mediated TH and AChE induction and have provided pharmacological evidence that TH induction involves a post-transcriptional, polyadenylation-dependent event (blockable by 9-beta-arabinofuranosyladenine but not by alpha- amanitin), whereas AChE induction requires transcription (blockable by alpha-amanitin). DBH and PNMT appear to be regulated via the same mechanism as TH. The time course of TH induction is such that NGF must be continuously present for at least the first 36 hr (during which time TH levels remain unchanged), and then the entire increase takes place during the subsequent 12 hr. In contrast, AChE induction proceeds linearly with time of NGF exposure. These data suggest that there may be multiple mechanisms by which NGF regulates enzyme induction. We have also compared the effects of cAMP with those of NGF. As compared to NGF, cAMP produces a different pattern of enzyme induction (in addition to TH, DBH, PNMT, and AChE, dopa decarboxylase (DDC) is also induced), it acts rapidly (a 12-hr exposure produces the full effect), and it acts only at the transcriptional level (its effects are blocked by alpha-amanitin). These data provide evidence that cAMP does not act as a second messenger for NGF with regard to enzyme induction.
The action of cholinergic agonists on the squid stellate ganglion giant synapse
Authors: Stanley EF
Published: March 2018

Although the giant synapse in the squid stellate ganglion has served as a model in the understanding of the ionic and electrical changes that occur during the release of transmitter from nerve terminals, little is known about the pharmacology of this synapse or the identity of its neurotransmitter. In the present study, the suggestion that acetylcholine (ACh) is the excitatory transmitter at this synapse was tested by exploring the actions of cholinergic agents on the pre- and postsynaptic giant axons and on the excitatory postsynaptic potential (EPSP). A novel arterial perfusion technique that circumvents the diffusion barrier from the bathing medium to the synapse has been used to demonstrate a depolarizing action of ACh and its agonist carbachol on the post- but not the presynaptic axon. The cholinergic receptors are distinct from receptors activated by amino acids, such as glutamate, have a reversal potential of about -48 mV, are anion- permeable, and desensitize without blocking the EPSP. It is concluded that these receptors are involved in an inhibitory input onto the postsynaptic giant axon and, therefore, that ACh is most probably not the transmitter at the squid giant synapse.