bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of differentiation increases Met5-enkephalin and Leu5- enkephalin content in NG108-15 hybrid cells: an immunocytochemical and biochemical analysis
Authors: Braas KM , Childers SR , U'Prichard DC
Published: March 2018

Regulation of cellular content of the endogenous opioid peptides Met5- enkephalin and Leu5-enkephalin was investigated in neuroblastoma X glioma hybrid cells NG108-15 grown in both serum-supplemented and serum- free defined media. Untreated cells and cells induced to differentiate were stained using anti-Met5-enkephalin and anti-Leu5-enkephalin with the peroxidase-antiperoxidase immunocytochemical technique at the light microscopic level. In untreated NG108-15 cells grown in serum- supplemented medium, intense enkephalin-like immunoreactivity was localized in cell bodies and short processes of a select population of cells. The volume fraction of stained untreated cells remained constant throughout the time period investigated. When cells were induced to differentiate with N6,O2′-dibutyryl adenosine 3′:5′-cyclic monophosphate (dBcAMP) or 8-bromo cyclic adenosine monophosphate (1.0 mM) treatment for 5 days, staining was found throughout the cytoplasm of perikarya and the extensive processes which were expressed, and the volume fraction of stained cells increased over 2-fold. Receptor- mediated stimulation of adenylate cyclase by prostaglandin E1 (10 microM) for 5 days produced results similar to those with dBcAMP. Pure cultures of differentiated cells with intense staining were obtained by further treatment of cultures, grown in the presence or absence of dBcAMP, with arabinosylcytosine (araC). Untreated, dBcAMP-treated and araC-treated NG108-15 cells grown in defined medium expressed staining patterns and volume fractions of stained cells similar to those grown in serum-supplemented medium; sodium butyrate (1.0 mM), however, increased the volume fraction of stained cells grown in defined medium over 3-fold, whereas it had little effect on staining of cells grown with serum. The presence of both Met5- and Leu5-enkephalin-like activities in NG108-15 cells was confirmed in acid extracts of cells by radioreceptor assay after separation by reverse phase high pressure liquid chromatography. Induction of differentiation in NG108-15 cells by dBcAMP treatment increased the cellular concentration of both enkephalins to over 2 times the levels found in untreated cells. The biochemical analysis for Met5-enkephalin- and Leu5-enkephalin-like activity compared well with the immunocytochemical data indicating that the enkephalin content is correlated with the state of differentiation of NG108-15 cells.
Modification of a rapidly transported protein in regenerating nerve
Authors: Tedeschi B , Wilson DL
Published: March 2018

From 1 to 28 days after frog sciatic nerve damage, dorsal root ganglia were incubated with [35S] methionine, and the labeled, rapidly transported proteins at various points along the nerve were analyzed on two-dimensional gels. The results show a dramatic increase in the labeling of a protein, which we have designated as A25, only after the arrival of the rapidly transported proteins at regenerating nerve tips. This effect is first seen 3 to 5 days after injury. On gels from regenerating nerves, A25 appears as a series of intense spots with an apparent molecular weight of 70,000. A25 is retrogradely transported from the regenerating nerve tip regions. Since labeled A25 increases only after the rapidly transported proteins reach regions of nerve containing regenerating axons, we conclude that it most likely arises from post-translational modification of a transported protein. Various experiments were conducted to rule out alternative sources of A25 labeling at the nerve periphery.
Development of motor innervation of the chick following dorsal-ventral limb bud rotations
Authors: Ferguson BA
Published: March 2018

To test mechanisms which motoneurons may use to grow to their appropriate targets, I rotated the limb around the dorsal-ventral axis prior to motoneuron outgrowth. The positions of motoneurons in the spinal cord innervating individual muscles and muscle masses were then determined using retrograde horseradish peroxidase uptake. Motoneurons innervated their appropriate muscles after dorsal-ventral limb rotation, before and after motoneuron death. Thus, cell death does not serve to remove errors in matching between motor nuclei and their corresponding muscles after dorsoventral rotation of the limb. Motoneurons must be specified for a peripheral target prior to outgrowth, and they grow to that target relatively directly. Axons compensated for the limb rotation by first collecting into groups in a position appropriate for the normal limb orientation, then shifting dorsal-ventral position within the plexus and proximal nerve trunk. Based on these results it is hypothesized that axons destined to innervate dorsal or ventral musculature might use chemospecific cues during growth to maintain appropriate positions within the nerve with respect to limb orientation.
Selective loss of acetylcholine sensitivity in a nerve cell line cultured in hormone-supplemented serum-free medium
Authors: Mitsuka M , Hatanaka H
Published: March 2018

When clonal rat pheochromocytoma PC12h cells were cultured in a hormone- supplemented serum-free medium, the carbamylcholine-elicited catecholamine release from cells cultured in serum-free medium was completely abolished. On the other hand, the high potassium-induced catecholamine release was not changed, even in PC12h cells cultured in serum-free medium. The lack of carbamylcholine sensitivity was confirmed directly by measuring carbamylcholine-induced 22Na influx, which was completely abolished in PC12h cells cultured in serum-free medium. The loss of carbamylcholine-induced 22Na influx seemed to obey nearly first-order kinetics and was fully restored upon a re-exposure to serum. The half-time for the loss was about 1 day, and the cultivation for 5 days in serum-free medium caused a 95% decrease of the nicotinic sensitivity in PC12h cells. The carbamylcholine-induced 45Ca influx into cells also was lost due to the serum-free cultivation. By contrast, the binding of alpha-bungarotoxin, which is an antagonist of nicotinic acetylcholine receptor in muscular cells, remained and did not change in PC12h cells cultured, even in the serum-free medium. In addition, veratridine-dependent 22Na influx and high potassium-induced 45Ca influx into cells, and high potassium-induced 86Rb efflux from cells cultured in the serum-free medium were also perfectly preserved. These results suggest that PC12h cells cultured in the serum-free medium seemed to be a useful model for comparing the differential mechanisms between acetylcholine sensitivity and other membranous functions on this cell.
On and off sublaminae in the lateral geniculate nucleus of the ferret
Authors: Stryker MP , Zahs KR
Published: March 2018

Like the retinal ganglion cells from which they receive their input, most relay neurons in the lateral geniculate nucleus have ON- or OFF- center receptive fields with antagonistic surrounds. In the cat, neurons with these two types of receptive fields are anatomically intermingled, even though the ON and OFF systems are functionally segregated. In the ferret, there is a sublamination of the retinal input to lateral geniculate nucleus laminae A and A1. We have investigated the function of this sublamination by making microelectrode recordings and have found that each sublamina consists of geniculate neurons of a single center type.
Muscarinic receptor binding and oxidative enzyme activities in the adult rat superior cervical ganglion: effects of 6-hydroxydopamine and nerve growth factor
Authors: Dombrowski AM , Jerkins AA , Kauffman FC
Published: March 2018

Administration of 6-hydroxydopamine to adult rats results in changes in the superior cervical ganglion similar to those noted after axotomy; namely, a decrease in muscarinic receptor binding and increases in activities of the oxidative enzymes of the pentose phosphate pathway. These changes were either prevented or attenuated markedly by the systemic administration of nerve growth factor. Administration of nerve growth factor alone did not significantly increase N-methylscopolamine binding in the ganglion or reduce the activities of the oxidative enzymes. Explants of the ganglion maintained in serum-free medium over a period of 3 days demonstrated increases in oxidative enzyme activity and a decrease in N-methylscopolamine binding. Addition of 20 nM nerve growth factor to the culture medium prevented the decline in N- methylscopolamine binding in ganglion explants. The increases in oxidative enzyme activities were unaltered. Addition of high amounts of nerve growth factor, 200 nM, resulted in a significant increase in tyrosine hydroxylase activity but no further increase in N- methylscopolamine binding in ganglion explants. Glucocorticoids added to the culture medium did not affect the muscarinic binding or enzyme activities. Thus, decreases in muscarinic binding activity which occur in the superior cervical ganglion after axotomy or 6-hydroxydopamine treatment may be explained by a loss of nerve growth factor supplied to the ganglion. Increases in the oxidative enzymes of the pentose phosphate pathway that occur in the ganglion after axonal injury appear to involve additional factors.
Immunohistochemical localization of bombesin/gastrin-releasing peptide and substance P in primary sensory neurons
Authors: Panula P , Hadjiconstantinou M , Yang HY , Costa E
Published: March 2018

The existence of bombesin/gastrin-releasing peptide-like immunoreactivity (BN-GRP-LI) in rat sensory ganglia and spinal cord was confirmed using immunocytochemistry, gel filtration chromatography, and high performance liquid chromatography combined with radioimmunoassay. Immunohistochemical studies showed that in the spinal sensory ganglia of the rat about 5% of the neurons exhibited BN-GRP-LI, whereas about 20% of the neurons exhibited substance P-like immunoreactivity (SP-LI). The two immunoreactivities were found in different cells, but both were located in small ganglion cells. In the posterior horn of the spinal cord, BN-GRP-LI and SP-LI were located in the superficial layers, and this distribution was different from that of Met5-enkephalin-like immunoreactivity. The results are in agreement with the concept that there is a primary sensory pathway from the sensory ganglia to the spinal cord which contains BN-GRP-LI and that these neurons are separate from those containing substance P. In extracts prepared from spinal ganglia, two molecular weight forms of BN-GRP-LI were found using gel filtration chromatography. The high molecular weight form coeluted with porcine GRP and the low molecular weight form was smaller than bombesin. The low molecular weight BN-GRP-LI extracted from spinal cord was more hydrophilic than bombesin or ranatensin.
Immunocytochemical localization of glutamic acid decarboxylase in normal and deafferented superior colliculus: evidence for reorganization of gamma-aminobutyric acid synapses
Authors: Houser CR , Lee M , Vaughn JE
Published: March 2018

There is circumstantial evidence that GABAergic synaptic terminals in the superior colliculus might become reorganized in response to a loss of the retinal innervation of this brain region. The present investigation tests this possibility by identifying gamma-aminobutyric acid (GABA) neurons and their synaptic relationships with an immunocytochemical localization of the GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD), and by comparing these synaptic relationships in normal superior colliculus with those present 6 and 16 weeks after unilateral eye removal. In normal superior colliculus, light microscopy revealed a much denser concentration of GAD-positive reaction product in the superficial layers than in the intermediate and deep collicular layers. Most of this reaction product was contained within small, punctate structures, but GAD-positive somata and proximal dendrites also were observed. Electron microscopy showed that GAD was localized in numerous synaptic terminals, including those that were the presynaptic elements of dendrodendritic synapses. The vast majority of GAD-positive presynaptic elements formed symmetric synaptic junctions. In addition, GAD-positive profiles frequently were postsynaptic to unstained retinal terminals as well as presynaptic to unstained dendritic profiles and thus participated in serial synaptic relationships. Furthermore, both retinal and GAD-positive elements commonly were presynaptic to the same postsynaptic dendrite, and often these synaptic contracts were adjacent to each other. In deafferented specimens, profiles with the characteristics of retinal axon terminals were not observed, whereas there appeared to be no reduction of GAD- positive synaptic profiles. However, there was a marked and statistically significant increase in the proportion of GAD-positive presynaptic terminals that formed asymmetric synaptic contacts in superior colliculus deprived of retinal input. This change indicates that partial deafferentation induces a reorganization of GAD-positive synapses. The long-term presence of the GABA-synthesizing enzyme within reorganized synaptic terminals also suggests that such presynaptic elements could produce and, presumably, release neurotransmitter.
The ultrastructural localization of serotonin immunoreactivity in myelinated and unmyelinated axons within the medial forebrain bundle of rat and monkey
Authors: Azmitia E , Gannon P
Published: March 2018

Myelinated and unmyelinated serotonin-containing axons were demonstrated in the medial forebrain bundle of rats and monkeys with an antibody against serotonin (5-HT) conjugated to hemocyanin. The level of 5-HT in the brain was increased by pretreatment of animals with pargyline and L-tryptophan. The addition of nickel salts to the diaminobenzidine-peroxidase reaction mixture increased the intensity of the reaction product. Specific 5-HT immunoreactivity was observed to be localized to membrane-enclosed and membrane-attached compartments. 5-HT immunoreactivity was seen predominantly in unmyelinated axons (0.2 to 1.25 micron in diameter) surrounded by unlabeled processes. More than half of these 5-HT-immunoreactive fibers were in apposition with unreactive myelinated axons in the hypothalamus of both the rat (55%) and the monkey (54%). These appositions may provide the anatomical substrate for the observations that sprouting serotonergic fibers in the adult brain use myelinated axons for contact guidance. In addition to the unmyelinated fibers, intensely labeled myelinated axons (1.0 to 2.1 micron) were seen in the medial forebrain bundle of both rats and monkeys. The percentage of 5-HT-immunoreactive myelinated axons appeared greater in the monkey than in the rat (25.4% versus 0.7% of the total number of 5-HT-immunoreactive fibers, respectively). the observation of an increased number of myelinated 5-HT-immunoreactive axons in the monkey hypothalamus as compared to the rat supports the general hypothesis of a trend toward increased myelination during evolution.
Embryonic development of the leech nervous system: primary axon outgrowth of identified neurons
Authors: Kuwada JY , Kramer AP
Published: March 2018

This paper describes the embryonic development of the leech nervous system and focuses on the differentiation of two identified pressure sensory (P) neurons, the PD and PV neurons. In the adult leech the P neurons have distinctive cell body locations in the central nervous system (CNS), different peripheral axon branching patterns, and different receptive field territories in the skin. The embryonic P neurons also have distinct and reproducible locations in the CNS and have been studied with recording and dye-filled microelectrodes from the time the first growth cones are projected from their somata. The peripheral axons of the P neurons are among the earliest peripheral axons to develop and may play an important role in the formation of peripheral nerves. The first or primary peripheral axons of the P neurons grow directly to their separate target territories. The specificity of the P neurons for their targets is probably not due to temporal differences in the outgrowth of their primary axons. Instead, the PD neuron seems to exhibit a preference early in embryogenesis for the target of its primary axon despite an apparent opportunity to occupy the target of the PV primary axon. It is hypothesized that the primary peripheral axons of the P neurons are among the first axons projected from the CNS and follow environmental cues to reach and innervate their target territories.
Increased transport of 44,000- to 49,000-dalton acidic proteins during regeneration of the goldfish optic nerve: a two-dimensional gel analysis
Authors: Benowitz LI , Lewis ER
Published: March 2018

Proteins synthesized in goldfish retinal ganglion cells and rapidly transported to the terminals of regenerating optic nerves were analyzed by two-dimensional (2-D) gel electrophoresis. Among the rapidly transported components, the most dramatic change observed during regeneration was for a family of polypeptides having molecular weights between 44,000 and 49,000 (44-49K) and isoelectric points of 4.6 to 4.9. Studies using [35S]methionine as a metabolic precursor in the eye showed that these proteins are present in both membranous and soluble fractions of the optic tectum, particularly during early stages of regeneration. Contralateral visual pathways, left intact to serve as controls, showed only very low levels of the proteins. These labeling changes were quantified in double-isotope studies, in which proteins from intact and regenerating sides were differentially labeled with [3H]proline and [14C]proline, comigrated on 2-D gels, and then counted for 3H/14C ratios. The labeling change for the 44-49K acidic proteins relative to the intact state was found to be over 100-fold in some day 19 regeneration samples and about 30-fold on day 40. Silver-stained gels of a tectal membrane fraction also revealed increased levels of the 44-49K acidic proteins during regeneration, indicating that the observed synthetic changes are accompanied by a net accumulation of the proteins.
Optical monitoring of activity from many areas of the in vitro and in vivo salamander olfactory bulb: a new method for studying functional organization in the vertebrate central nervous system
Authors: Orbach HS , Cohen LB
Published: March 2018

We have investigated the use of voltage-sensitive dyes to monitor neuronal activity in the intact salamander olfactory bulb. After a 10- to 20-min staining period, a magnified image of an in vitro or an in vivo preparation was formed on a 124-element photodiode array. The array was used to simultaneously record absorption or fluorescence changes from 124 adjacent areas of the bulb. At the magnifications used, each detector received light from 100 to 1000 neurons. Relatively large absorption and fluorescence signals were found in response to olfactory nerve stimulation; all of the results presented were from single trials. Because of the large signal size, measurements on in vivo preparations using epi-illumination also had good signal-to-noise ratios. There were significant differences in signal time course between adjacent detectors which suggested a spatial resolution on the order of 200 microns. Tentative assignments of the cellular origins of some signals could be made from the results of paired volley experiments. The results suggest that optical monitoring of membrane potential could provide a useful method for studying neuronal organization in the intact vertebrate central nervous system.
Serotonin and octopamine have opposite modulatory effects on the crayfish's lateral giant escape reaction
Authors: Glanzman DL , Krasne FB
Published: March 2018

Serotonin and octopamine have opposite effects on a simple behavioral response, the crayfish's lateral giant escape reaction. Specifically, serotonin depresses the lateral giants' responsiveness, whereas octopamine enhances it. Both effects are largely confined to the disynaptic pathway from the sensory afferents to the lateral giants, although, occasionally, small effects are also seen in the monosynaptic pathway to the lateral giants. One specific locus of the octopaminergic effect is the synapse between the afferents and the largest of the sensory interneurons in the disynaptic pathway, interneuron A. Serotonin, however, does not have a consistent effect at this synapse. Although serotonin and octopamine modulate the excitability of the escape response, neither monoamine appears to significantly alter the rate at which this response habituates.
Two distinct solubilized benzodiazepine receptors: differential modulation by ions
Authors: Lo MM , Snyder SH
Published: March 2018

The modulation of solubilized type 1 and type 2 benzodiazepine receptors from cow brain by gamma-aminobutyric acid (GABA), divalent cations, and anions has been evaluated. GABA stimulates [3H] flunitrazepam binding of both receptor subtypes, whereas divalent cations and anions selectively stimulate solubilized type 2 receptors. Of numerous anions examined, only chloride, bromide, and iodide enhance [3H] flunitrazepam binding. Chloride and bromide increase mainly receptor affinity for [3H]flunitrazepam, whereas iodide largely influences Bmax values. Divalent cations also stimulate soluble type 2 receptors. Calcium, zinc, manganese, barium, and magnesium have similar potencies in enhancing [3H]flunitrazepam binding, whereas copper and nickel are about 4 to 5 times more potent. The 2- to 3-fold increase in type 2 receptor binding by divalent cations involves change in numbers of binding sites. Effects of combinations of GABA, calcium, and chloride suggest that they may exert their modulating effects on type 2 receptors through different mechanisms. GABA, calcium, and chloride also protect [3H]flunitrazepam binding from heat inactivation, indicating a close link in the native state between the GABA, ions, and the benzodiazepine recognition sites. Since physiologic concentrations of calcium and chloride influence type 2 receptors, these ions may be involved in those pharmacologic effects of benzodiazepines mediated by type 2 sites.
Identification of central cholinergic neurons containing both choline acetyltransferase and acetylcholinesterase and of central neurons containing only acetylcholinesterase
Authors: Eckenstein F , Sofroniew MV
Published: March 2018

Neurons in the rat central nervous system (CNS) were examined for their content of both the acetylcholine-synthesizing enzyme, choline acetyltransferase (ChAT; acetyl-CoA, choline O-acetyl-transferase, EC 2.3.16), and the transmitter-degrading enzyme, acetylcholinesterase (AChE). ChAT was localized immunohistochemically and AChE was localized histochemically in normal, colchicine-treated, or diisopropylfluorophosphate (DFP)-treated rats, either in neighboring sections by standard procedures or simultaneously in the same sections by immunofluorescence for ChAT, followed by photography, followed by histochemistry for AChE, followed by brightfield rephotography of the same neurons. This combination of fluorescence and brightfield procedures allows both to be carried out at maximum intensity without fear of interference and enables the unambiguous visualization of all neurons that might be expected with either procedure. Based on previous examination of singly stained neighboring sections, five CNS areas were examined in detail in DFP-treated rats using the simultaneous procedure for localizing both ChAT and AChE in the same neurons in the same sections. Several hundred neurons were thus examined in each area. These areas were the caudate putamen, nucleus basalis of Meynert, medial septum, nucleus of the diagonal band of Broca (vertical and horizontal limbs), and zona incerta. In the caudate putamen and nucleus basalis magnocellularis of Meynert, all ChAT-positive neurons contained AChE and vice versa. In the medial septum and nucleus of the diagonal band of Broca, all ChAT-positive neurons contained AChE, but these neurons containing both ChAT and AChE were intermingled with neurons positive only for AChE.(ABSTRACT TRUNCATED AT 250 WORDS)
Ascending projections to the medial geniculate body of the cat: evidence for multiple, parallel auditory pathways through thalamus
Authors: Calford MB , Aitkin LM
Published: March 2018

The sources of ascending input to the medial geniculate body (MGB) of the cat were studied using the retrograde transport of horseradish peroxidase (HRP). HRP injections were made iontophoretically through micropipettes which were also used to record physiological properties at the injection sites. This technique produced small injections which appeared to be restricted to single subnuclei. The tectothalamic projection of the auditory system was found to consist of at least four distinct and separate pathways. The ventral division of the MGB receives a topographical projection from the central nucleus of the inferior colliculus (ICC) which preserves tonotopicity and provides short latency, sharply frequency-tuned responses. The medial part of the ICC projects to the deep dorsal nucleus, which contains only units tuned to high frequencies. The major inputs to the caudodorsal nucleus (DC) stem from nucleus sagulum and the pericentral nucleus of the inferior colliculus (ICP). Units in DC and the ventrolateral nucleus, which also receive input from ICP, have very broad tuning properties and late, habituating responses. Injections of HRP into the medial division (MGM) produced labeled cells scattered throughout the external nucleus of the inferior colliculus and the ventral part of ICC. This widespread input is reflected in the wide range of auditory responses found in MGM. Auditory responses in the suprageniculate nucleus were poorly defined and many units did not respond to tonal stimuli; following HRP injections no filled cells were found in the inferior colliculus, but labeled cells were found in the deeper layers of the superior colliculus and in the interstitial nucleus of the brachium of the inferior colliculus. Together with recent findings on the auditory thalamocortical projection, these results provide evidence for multiple parallel auditory pathways through the thalamus.
Properties of neurons from dissociated fetal rat brain in serum-free culture
Authors: Ahmed Z , Walker PS , Fellows RE
Published: March 2018

Because of the unknown constituents and varying composition of serum, its presence in media used in cell culture unavoidably compromises attempts to study cellular mechanisms of growth and differentiation. To overcome this, we have devised a serum-free, chemically defined medium which maintains primary cultures of fetal rat brain cells for more than 6 weeks. This medium allows expression of characteristic properties of neurons and prevents overgrowth of non-neuronal elements without use of antimitotic agents. Cells prepared and plated without exposure to serum attach in less than 20 min to poly-D-lysine substratum and begin to extend processes within 1 hr. After 2 days in culture, process-bearing cells can be divided into those with characteristic neuronal morphology, including long processes which generally branch at a distance from the perikaryon, and those having the appearance of glial cells with many short, thin processes which branch frequently near the cell body. The remaining non-neuronal cells are large and flat with few or no processes. The presence of neurons and astroglia was demonstrated by immunofluorescence detection of bound tetanus toxin as a neuron- specific surface marker, and glial fibrillary acidic protein as an astroglial marker. By the 3rd day in culture, many cells of neuronal morphology were able to generate action potentials in response to electrical stimulation. The ionic composition of the inward current changes from Ca2+ to predominantly Na+ by about 10 days in culture. The presence of synaptic vesicles and myelin was demonstrated by electron microscopy. The ability of dissociated cells from mammalian brain to grow in defined medium without serum and acquire selected properties of mature cells in vivo demonstrates the potential of this culture system for neurobiological studies at the cellular level.
The activity of neurons in the rostral medulla of the rat during withdrawal from noxious heat
Authors: Fields HL , Bry J , Hentall I , Zorman G
Published: March 2018

Neurons of the rostral ventromedial medulla (RVM) have been implicated in the modulation of nociceptive transmission. In order to further analyze their role in pain behavior, we studied their activity while eliciting the tail flick reflex with noxious heat. Recording sites were regions in the RVM from which microstimulation (less than or equal to 10 microA, 400 mu sec, 50 Hz continuous pulse trains) inhibited the tail flick reflex. Extracellular unit activity and tail temperature were recorded, stored, and plotted with reference to either the time of tail flick or the time when the stimulating temperature reached 45 degrees C. Neuronal discharges were found to be either increased (on- cells), decreased (off-cells), or unchanged around the time of the tail flick. The decreases in discharge were more closely correlated with the tail flick behavior than with the temperature of the stimulus. These off-cells were located at sites of lowest threshold for tail flick inhibition and tended to be ventral to on-cells. We propose that off- cells must pause if the tail flick is to occur, and that this pausing allows the transmission of nociceptive input through spinal reflex loops.
Identified Aplysia neurons form specific chemical synapses in culture
Authors: Camardo J , Proshansky E , Schacher S
Published: March 2018

Identified neurons from the abdominal ganglion of the marine mollusc Aplysia californica make specific transmitter-mediated synapses in dissociated cell culture. The cholinergic interneuron L10 makes synapses in vitro with one group of its follower cells, the left upper quadrant cells, and these connections exhibit the features of these synapses in vivo when the postsynaptic cells are plated with their initial axon segments. Furthermore, L10 will avoid making synapses with right upper quadrant cells, which contain cholinergic receptors but do not synapse with L10 in vivo. This in vitro system can therefore be used as a model in which to study the development of specific neuronal connections.
Conditioned modification of locomotion in Hermissenda crassicornis: analysis of time-dependent associative and nonassociative components
Authors: Crow T
Published: March 2018

The contribution of associative and nonassociative factors to the conditioned modification of phototactic behavior in Hermissenda was examined after varying the number of conditioning trials and the time between training and testing. Five or 10 conditioning trials did not produce significant changes in phototactic behavior when tested immediately after training. Both 5 and 10 conditioning trials resulted in significant short-term nonassociative changes in behavior (resembling sensitization) when the time between training and testing was 15 min or longer. Following 50 conditioning trials (single session training), nonassociative effects made the major contribution to the change in behavior when the post-training test interval was 30 min. These nonassociative changes decremented during a 1-hr period following training. Significant associative effects were observed 45 min after 50 conditioning trials; however, significant associative effects were not observed when the same animals were tested 24 hr after training. With 3 days of training (multiple session training-150 trials), associative effects were found 30 min after training and nonassociative effects again showed a rapid decrement during the 1-hr period following the end of training. The associative effects observed soon after training were persistent during the retention period and showed significant effects 24 hr after training. These data indicate that (1) the behavioral effects found after single session training (5 and 10 trials) are nonassociative, and (2) these nonassociative effects do not increase significantly over the course of multiple session training.(ABSTRACT TRUNCATED AT 250 WORDS)
Development of prestriate visual projections in the monkey and human fetal cerebrum revealed by transient cholinesterase staining
Authors: Kostovic I , Rakic P
Published: March 2018

Cholinesterase (ChE) staining was used to reveal the timing and pattern of development of afferents to the prestriate visual cortex (areas 18, 19, 20, and 21 of Brodmann) in a series of developing human and monkey fetal brains. This investigation was possible because the nucleus pulvinaris of the thalamus, the main source of subcortical projections to the prestriate cortex, displays positive reactivity after thiocholine incubation during the last three quarters of gestation, while neighboring thalamic nuclei that project to the adjacent neocortical areas are unstained. Staining of the pulvinar and its prestriate projections passes through six broad stages. Stage I begins in both species at the end of the first third of gestation. Positively stained fibers originate from the pulvinar and enter but do not extend beyond the hemispheric stalk. During stage II, pulvinar axons gradually invade the intermediate zone of the occipital lobe, and in stage III they reach the level of the subplate zone. In stage IV, which occurs around mid-gestation in both species, cholinesterase-positive fibers accumulate within the subplate zone subjacent to the developing prestriate cortex. During stage V, ChE-positive fibers penetrate the prospective prestriate cortex but do not yet form the alternating columnar pattern characteristic of pulvinar input to this area in the adults. Rather, ChE activity is concentrated in two continuous bands situated within prospective layers III-IV and VI; also a narrow band is visible in upper layer I. In stage V a clear histochemical border forms between prestriate and striate areas with ChE activity in prospective area 17 limited mostly to the superficial strata of layers I and II. This histochemical differentiation precedes the emergence of cytoarchitectonic landmarks. During stage VI, which begins in the last fifth of gestation in both species, the pulvinar become progressively less stainable and its projections can no longer be traced by ChE histochemistry.
Basic optokinetic-ocular reflex pathways in the frog
Authors: Cochran SL , Dieringer N , Precht W
Published: March 2018

Frogs (Rana temporaria) have two midbrain nuclei that receive contralateral retinal afferents, and whose neurons respond to optokinetic stimulation. The basal optic nucleus is composed of direction-selective neurons with different response types. One type is activated exclusively by upward moving optokinetic targets; another type is activated only by downward moving targets. Two other types of basal optic neurons show this vertical preference, but each is also activated by patterns moved horizontally from the nasal to temporal visual field. No activation of these cells was found with patterns moved horizontally from the temporal to nasal visual fields. Rather, cells in a discrete pretectal region have this type of sensitivity: they increase their resting rate with temporal to nasal stimulation and decrease it with nasotemporal stimulation. Oculomotor neurons (antidromically identified) have similar optokinetic sensitivities. As with basal optic neurons, these cells have exclusively upward or downward sensitivity, and some also have nasotemporal sensitivity. An additional type of oculomotor neuron and abducens motoneurons are activated by temporonasal pattern movement. In general, the extraocular motoneurons have similar velocity and pattern size preferences, as have the sensory nuclei. Investigations of the connectivity between the sensory and motor nuclei were primarily restricted to the relation between the pretectum and the abducens. A monosynaptic connection between the pretectum and the abducens is suggested by four points: (1) excitatory postsynaptic potential onset latency in antidromically identified abducens motoneurons, following optic nerve stimulation, is consistent with the interpretation of a disynaptic pathway to the abducens from the retina; (2) pretectal cells, sensitive to optokinetic stimulation, can be activated antidromically from stimulation of the abducens nucleus; (3) horseradish peroxidase injections into the pretectum result in labeling of axons, which terminate in the abducens nucleus; (4) horseradish peroxidase injections into the abducens result in labeling of cells in the pretectal region, where optokinetically sensitive cells are found. In the frog, there seem to be three-neuronal retino-ocular reflexes mediating optokinetic slow phase behavior as there are three-neuronal vestibulo-ocular reflexes that also mediate compensatory spatial behavior. It is suggested that these direct connections act to initiate ocular movements and accelerate the eye, whereas more indirect pathways may act to maintain eye position.
DARPP-32, a dopamine- and adenosine 3':5'-monophosphate-regulated phosphoprotein enriched in dopamine-innervated brain regions. III. Immunocytochemical localization
Authors: Ouimet CC , Miller PE , Hemmings HC , Walaas SI , Greengard P
Published: March 2018

Immunocytochemical studies have been carried out to determine the regional and cellular distribution of DARPP-32, a protein the phosphorylation of which can be regulated by dopamine and cAMP in intact cells. These immunocytochemical studies indicate tha DARPP-32 is localized primarily in those brain regions enriched in dopaminergic nerve terminals. Moreover, the staining pattern supports the conclusion that the DARPP-32 is present in dopaminoceptive neurons, i.e., neurons that receive a dopamine input, and that it is absent from the dopaminergic neurons themselves. Within the caudatoputamen, nucleus accumbens, olfactory tubercle, bed nucleus of the stria terminalis, and portions of the amygdaloid complex, all of which receive a strong dopamine input, DARPP-32 immunoreactivity is present in neuronal cell bodies and dendrites. In brain regions that are known to receive projections from these nuclei, puncta (presumed nerve terminals) are strongly immunoreactive for DARPP-32 but indigenous cell bodies and dendrites are not immunoreactive. These target areas include the globus pallidus, ventral pallidum, entopeduncular nucleus, and the pars reticulata of the substantia nigra. No immunoreactivity is detected in neuronal cell bodies or dendrites in any of the dopaminergic nuclei. Furthermore, nerve terminals immunoreactive for DARPP-32 do not resemble dopaminergic varicosities in either their morphology or their pattern of distribution. Many neurons are weakly immunoreactive for DARPP-32 and some of these are found in areas that apparently lack a dopaminergic input: weakly labeled neuronal cell bodies and dendrites were found throughout the neocortex, primarily in layer VI, and in the Purkinje neurons of the cerebellum. DARPP-32 immunoreactivity is also present in certain glial cells, especially in the median eminence, arcuate nucleus, and medial habenula. The present immunocytochemical studies, taken together with biochemical studies (Hemmings, H.C., Jr., A.C. Nairn, D.W. Aswad, and P. Greengard (1984) J. Neurosci. 4: 99–110; Walaas, S.I., and P. Greengard (1984) J. Neurosci. 4: 84–98) on DARPP- 32, indicate that DARPP-32, is present in the subclass of dopaminoceptive neurons containing D-1 receptors (dopamine receptors coupled to adenylate cyclase). DARPP-32 may be an effective marker for certain of the actions of dopamine that are mediated through cAMP and its associated protein kinase.
The laminar organization of the lateral geniculate body and the striate cortex in the tree shrew (Tupaia glis)
Authors: Conley M , Fitzpatrick D , Diamond IT
Published: March 2018

The organization of geniculostriate projections in Tupaia was studied using three separate methods, anterograde transport from the lateral geniculate, retrograde transport from the striate cortex, and reconstruction of single geniculostriate axons. The results show that each layer of the lateral geniculate body has a unique pattern of projections to the striate cortex, and each pattern consists of a major and a minor target. The two ipsilateral layers project to thin subtiers of layer IV: the major target of geniculate layer 1 is the top of IVa; the major target of geniculate layer 5 is the base of IVb. The minor target of layer 1 is the major target of layer 5. Two of the contralateral layers can be matched to the ipsilateral layers. Layers 1 and 2 are a matched pair and project to IVa; layers 4 and 5 are a matched pair and project to IVb. Thus, projections of a matched pair overlap. The remaining two contralateral layers, 3 and 6, project chiefly to cortical layer III. Layer 3 projects to layers IIIb and I and seems to be the counterpart of the parvocellular C layers in the cat and the intercalated layers in primates. Layer 6 projects to the base of IIIc in a zone contiguous with IVa. This contiguity raises the issue of whether the base of IIIc might actually be a part of layer IV. If this were the case, the two tiers of layer IV which are separated by a conspicuous cleft might be considered two subdivisions of layer IVb.
Monoclonal antibodies to specific astroglial and neuronal antigens reveal the cytoarchitecture of the Bergmann glia fibers in the cerebellum
Authors: de Blas AL
Published: March 2018

The cytoarchitecture of the cerebellar Bergmann fibers in the adult rat was investigated. Two monoclonal antibodies, one specific for the Bergmann fibers and astrocyte processes and the other specific for the cell bodies and dendrites of the Purkinje cells as well as an antiserum to the glial fibrillary acidic protein, were used in immunocytochemical peroxidase-antiperoxidase assays. The Bergmann fibers are revealed as columns organized in long vertical palisades parallel to the longitudinal plane of the folium. The palisades are not continuous; instead they are formed by sets of two to six aligned Bergmann fibers. Each of these sets of Bergmann fibers is separated from its longitudinally aligned neighbors by gaps. Each Bergmann fiber is formed by a bundle of two to four Bergmann glia processes which frequently show a helical organization. These results help to reconcile the different views on the organization of the Bergmann fibers derived from the studies done with the light microscope versus those done with the electron microscope. The Bergmann glia may play a fundamental role in directing the geometrical organization of the cerebellar constituents.
Passive cable properties of dendritic spines and spiny neurons
Authors: Wilson CJ
Published: March 2018

A cable model of the linear properties of dendritic spines was generated using the Laplace transform technique. Analytical solutions for the voltages generated in the spine by a current impulse at the spine head were used in a numerical procedure for simulating the effect of a synaptic conductance change. The synaptic current produced by the conductance change was used as an input for evaluation of the postsynaptic potential and current injected into the dendrite at the base of the spine. The primary effect of the dendritic spine was to attenuate synaptic current. This effect was produced by the high input impedance at axospinous synapses, which resulted in giant spike-like excitatory postsynaptic potentials (EPSPs) that approached the reversal potential of the synapse and thus reduced the potential gradient driving the synaptic current. Although virtually all of the synaptic current was transferred to the dendrite, it produced much smaller EPSPs there due to the low dendritic input impedance. Very small conductance changes produced near maximal synaptic currents in dendritic spines. The current attenuating effect of the spine was accentuated with brief synaptic transients and reduced with prolonged synaptic conductance changes. The size and shape of the spine head, and the diameter and boundary conditions of the dendrite had little or no effect on current attenuation for spines in the naturally occurring size range. The diameter and length of the spine stalk and the size and location of the spine apparatus were the key morphological factors determining the synaptic currents generated by axospinous synapses. Naturally occurring size and shape differences among dendritic spines produced large differences in synaptic potency when compared in a model spiny neuron based on the neostriatal spiny projection neuron. These differences were comparable to those produced by differences in synaptic-location on the same neuron.
Effects of reaction time performance on single-unit activity in the central auditory pathway of the rhesus macaque
Authors: Ryan AF , Miller JM , Pfingst BE , Martin GK
Published: March 2018

The activity of single units at various locations in the central auditory pathway of rhesus macaques was recorded during the monkeys' performance and nonperformance in an auditory reaction time task. Evoked unit responses during performance were compared with those observed during passive delivery of identical stimuli. Single units were recorded from the cochlear nucleus, superior olivary complex, lateral lemniscus, inferior colliculus, medial geniculate nucleus, and auditory cortex. Significant effects of task performance on unit discharge patterns were observed at all levels of the central auditory pathway: Spontaneous discharge rates in the more peripheral auditory nuclei tended to be higher during performance. Evoked discharge that occurred relatively late during a stimulus presentation (greater than 75 msec after stimulus onset) was increased during performance, compared with the nonperformance condition, in nuclei above the cochlear nucleus. The initial latency of evoked discharge was increased during performance for subcortical nuclei but was decreased for units in auditory cortex. These results suggest that the effects of performance may be mediated by a tonic increase in the excitability of auditory units which operates primarily at peripheral auditory stations, and a descending, stimulus-evoked increase in excitability which primarily influences the cells of higher auditory nuclei. At the cortical level, these changes lead to increased signal-to-noise ratio of the evoked response during performance in the auditory task.