bluuebunny/crossref_metadata_2025 huggingface dataset:
Lateral hypothalamic modulation of the gustatory-salivary reflex in rats
Authors: Matsuo R , Kusano K
Published: March 2018

It is well recognized that the basic mechanism for the gustatory- salivary reflex is located in the lower brainstem and that suprabulbar structures possibly influence this mechanism. This study is designed to evaluate the neurophysiological mechanism underlying the effect of the lateral hypothalamic area (LHA) on the bulbar gustatory-salivary reflex. Submandibular salivary secretion and the electrical activity of the preganglionic parasympathetic fibers innervating the submandibular and sublingual glands were recorded in anesthetized rats. Stimulation of the tongue with high concentrations of chemical solutions (1 M and 2 M NaCl and 0.01 M and 0.05 M HCl) and/or pinching the tongue with a small clamp induced a profuse salivary secretion (3 to 28.5 microliter/5 min) recorded from a unilateral submandibular gland. The preganglionic fibers consisted of three types: taste-related fibers, which increased their firing rate by taste stimuli; pinch-related fibers, which increased their firing rate by pinching; and unidentified fibers, which did not respond to taste or pinching stimulations of the tongue. Electrical stimulation of the ipsilateral LHA caused the secretion of a small amount of saliva (1.5 microliter/5 min), and it appeared that taste-related fibers more often received polysynaptic connections from the LHA than other types of fibers. Conditioning stimulation of the LHA increased the magnitude of impulse discharges by the test stimulation of the tongue in the taste-related fibers. Therefore, the results of this study demonstrate that the LHA enhances the activity of the gustatory-salivary reflex in the lower brainstem.
Neurogenesis in Aplysia californica resembles nervous system formation in vertebrates
Authors: Jacob MH
Published: March 2018

The pattern of neurogenesis of the central nervous system of Aplysia californica was investigated by [3H]thymidine autoradiography. Large numbers of animals at a series of early developmental stages were labeled with [3H]thymidine for 24 or 48 hr and were subsequently sampled at specific intervals throughout the life cycle. I found that proliferative zones, consisting of columnar and placodal ectodermal cells, are established in regions of the body wall adjacent to underlying mesodermal cells. Mitosis in the proliferative zones generates a population of cells which leave the surface and migrate inward to join the nearby forming ganglia. Tracing specific [3H]thymidine-labeled cells from the body wall to a particular ganglion and within the ganglion over time suggests that the final genomic replication of the neuronal precursors occurs before the cells join the ganglion while glial cell precursors and differentiating glial cells continue to divide within the ganglion for some time. Ultrastructural examination of the morphological features of the few mitosing cells observed within the Aplysia central nervous system supports this interpretation. The pattern of neurogenesis in the Aplysia central nervous system resembles the proliferation of cells in the neural tube and the migration of neural crest and ectodermal placode cells in the vertebrate nervous system but differs from the pattern described for other invertebrates.
Embryonic cerebellar neurons accumulate [3H]-gamma-aminobutyric acid: visualization of developing gamma-aminobutyric acid-utilizing neurons in vitro and in vivo
Authors: Hatten ME , Francois AM , Napolitano E , Roffler-Tarlov S
Published: March 2018

gamma-Aminobutyric acid (GABA) is the proposed neurotransmitter for four types of cerebellar neurons-Purkinje, Golgi, basket, and stellate neurons. With this investigation we have begun studies to establish when these neurons acquire their neurotransmitter “identification.” Autoradiographic studies of both cultured embryonic (embryonic day 13) cerebellar cells and of intact embryonic cerebellum (embryonic day 13) were conducted with tritiated GABA. Two to 5% of the embryonic cerebellar cells accumulated [3H]GABA in vitro. By morphological and immunocytochemical criteria, labeled cells were large neurons with either a thick, apical process, a multipolar shape, or were bipolar with longer processes. The identification of cells which accumulated [3H]GABA as neuronal precursors was supported by the differential sensitivity to drugs that preferentially inhibit accumulation of [3H]GABA by neurons and glia. The results of the in vitro experiments were confirmed and extended with in vivo experiments. When intact cerebellar tissue was removed at embryonic day 13, stripped of meninges and choroid plexus, exposed to low concentrations of [3H]GABA, and processed for light microscopic autoradiography, heavily labeled cells were seen in the middle of the cerebellar anlage. Labeled cells were not seen in the ventricular zone of proliferating neuroblasts lining the fourth ventricle or in the external granular layer emerging at the lateral aspect of the pial surface. The accumulation of [3H]GABA by these cells also showed the pharmacological characteristics of uptake by neurons. This study shows that among migrating, immature forms of the larger neurons of the embryonic cerebellum, there is a select group which accumulates [3H]GABA and other classes of cells which do not. These results indicate very early acquisition of transmitter expression by cerebellar neurons, far in advance of their final positioning and establishment of synapses.
Localization and characterization of gastrin/cholecystokinin-like immunoreactivity in the central nervous system of Aplysia californica
Authors: Vigna SR , Morgan JL , Thomas TM
Published: March 2018

Gastrin/cholecystokinin-like immunoreactivity (G/CCK-LI) was localized by immunocytochemistry in neurons in the central nervous system of Aplysia californica. Neuronal cell bodies were specifically immunostained in the buccal, cerebral, pedal, and abdominal ganglia but not in the pleural ganglia. Neural G/CCK-LI processes were observed in the neuropil of all ganglia and connectives and in some but not all of the peripheral nerves examined. Somata containing G/CCK-LI ranged from 15 to 200 micron in diameter. Ganglionic G/CCK-LI was most efficiently extracted in neutral or basic solutions and consisted mainly of a substance eluting in a volume corresponding to a peptide of between 8 and 17 amino acid residues on gel filtration. This G/CCK-LI diluted in parallel to mammalian gastrin in radioimmunoassays using two antisera differing in their specificities for the bioactive COOH-terminal region of mammalian G/CCK. We conclude that G/CCK-LI is distributed widely in the central and peripheral nervous systems of Aplysia californica and that this immunoreactivity probably represents a small peptide which is similar but not identical to mammalian gastrins and cholecystokinins at the functionally critical COOH terminus.
Paths of axons in the visual system of perciform fish and implications of these paths for rules governing axonal growth
Authors: Rusoff AC
Published: March 2018

The optic nerve of many perciform fish is ribbon-shaped, and axons from ganglion cells in specific parts of the retina are consistently found in specific places in this ribbon. I utilized this organization to fill selected groups of axons with horseradish peroxidase. I then traced these groups of axons through the nerve and across the tectum to their terminal arbors. The paths of the axons suggest that axons use a number of different mechanisms to guide them to their correct terminal sites. At some points they appear simply to grow along the surface created by earlier axons, but at other points they seem to be using cues more complex than simple mechanical guidance. In addition, I have demonstrated that for every anulus of ganglion cells on the retina there is an anulus of terminal arbors on the tectum. With time the terminals in a given anulus must move caudally to keep the retinotopic map centered on the tectum while the tectum continues growing nonsymmetrically . I have shown both that the anuli of terminals do remain roughly centered on the tectum and that the predicted pattern of terminal movement is visible on the tecta of perciform fish.
Mitotic neuroblasts in the 9-day-old and 11-month-old rodent hippocampus
Authors: Kaplan MS , Bell DH
Published: March 2018

Ultrastructural identification of mitotic neuronal precursors beneath the basal hippocampal granule cell layer was made using electron micrographs of [3H]thymidine-labeled cells. Ultrathin sections were obtained by a method that allows serial thin sectioning of reembedded sections previously prepared for light microscopic radioautography. The electron microscopic observations reported in this study reveal: (1) that a steady rate of granule cell neurogenesis occurs during the first year of a rodent's life; (2) that newly formed granule neurons in the dentate gyrus of the newborn mouse and adult rat are a result of neuroblast division; and (3) two distinct classes of mitotic cells can be identified during the peak period of postnatal neurogenesis--those with synapses on their cell bodies and processes and those with no synapses or processes.
Do vasopressin-related peptides induce hippocampal corticosterone receptors? Implications for aging
Authors: Sapolsky RM , Krey LC , McEwen BS , Rainbow TC
Published: March 2018

The aged rat shows a decline in hippocampal corticosterone receptors and dysfunction in learning and adrenocortical physiology previously linked to glucocorticoid effects upon the hippocampus. The Brattleboro rat, congenitally lacking vasopressin, also has a low number of hippocampal glucocorticoid receptors, as well as learning and endocrine impairments similar to those seen in the aged. Centrally acting vasopressin analogues correct the receptor loss in the hippocampus in the Brattleboro rat but do not influence the hippocampal receptor deficit in the aged rat. Quantitative and high resolution autoradiographic procedures were utilized to characterize the glucocorticoid receptor deficit in the aged and Brattleboro rats. Quantitative autoradiography showed that in both aged and Brattleboro subjects, losses in receptors were most extreme in the pyramidal layer of the CA3a region. High resolution autoradiography revealed striking differences in the cellular basis of the receptor losses. Brattleboro rats had decreased binding of [3H]corticosterone per neuron, whereas aged subjects, in addition, had significant losses in the number of corticosterone-concentrating neurons. Taken together, our findings indicate that the glucocorticoid receptor deficit in the Brattleboro rat probably represents a vasopressin-influenced defect in the synthesis or degradation of the receptor, whereas in the aged rat the deficit originates from loss of both receptor per neuron and the steroid-concentrating neurons themselves, and thus is most likely a permanent and pharmacologically insensitive deficit.
Cellular interactions and pattern formation in the visual system of the branchiopod crustacean, Daphnia magna. III. The relationship between cell birthdates and cell fates in the optic lamina
Authors: Flaster MS , Macagno ER
Published: March 2018

The birthdates of nerve cells in the optic ganglion of the water flea Daphnia magna were determined using [3H]thymidine autoradiography. The analysis was aided by computer-assisted three-dimensional reconstruction and correlated with serial electron microscopy of the developing visual system. Previous work has shown that the projection from eye to optic ganglion is retinotopic at the level of single cells ( Macagno , E.R., V. LoPresti , and C. Levinthal (1973) Proc. Natl. Acad. Sci. U.S.A. 70: 433–437). Studies of both normal and perturbed development ( LoPresti , V.,E.R. Macagno , and C. Levinthal (1973) Proc. Natl. Acad. Sci. U.S.A. 70: 56–61; Macagno , E.R. (1978) Nature 275: 318–320) have suggested that retinotopy is a consequence of an invariant pattern of sequential growth and cellular interactions. We report here that the laminar cells, the first-order target cells of the visual projection, become postmitotic in an orderly fashion that correlates with their position and connectivity in the adult array. Furthermore, presumptive laminar cells complete their final division just prior to or during initial contact with the growing processes of the visual fibers with which they will form their mature retinotopic contacts. The correlation between times of final division of target cells and the arrival of visual fibers with which they interact provides further indirect evidence that sequential growth and cellular interactions are key factors in establishing normal connectivity in the visual system of arthropods.
Cutaneous responsiveness in primary somatosensory (S-I) hindpaw cortex before and after partial hindpaw deafferentation in adult rats
Authors: Wall JT , Cusick CG
Published: March 2018

The hindpaw of the rat is normally innervated by the sciatic and saphenous nerves. In the present studies, the hindpaws of adult rats were partially deafferented by transection of the sciatic nerve for variable periods of time. The organization of the hindpaw representation in primary somatosensory (S-I) cortex was then studied with neurophysiological mapping techniques and compared to the organization seen in normal rats. The objective was to determine whether cutaneous responsiveness was recovered in the cortical area which lost normal cutaneous inputs from the sciatic nerve, and, if recovery occurred, to characterize the time course and spatial extent of this recovery. Normal rats were found to have a topographically organized representation of the hindpaw in S-I cortex. As determined by nerve recording and cortical mapping, approximately 85% of this representation is responsive to cutaneous inputs from the sciatic nerve, while the remaining 15% is responsive to inputs from the saphenous nerve. Following transection of the sciatic nerve, all hindpaw skin regions normally innervated by the sciatic nerve remained denervated. In cortex, the representation of cutaneous inputs from the saphenous nerve expanded into parts of the hindpaw region normally representing sciatic inputs and occupied an area about 3 times larger than the saphenous representation in normal rats. This expansion was initially observed 1 to 2 days after transection and was stably maintained with longer deafferentation times. However, even after chronic deafferentation of up to 5 months, this enlarged saphenous representation was still only half the size of the normal hindpaw representation in normal rats. These findings suggest that cortical representations of deafferented skin can become activated by substitute cutaneous inputs. The rapid time course for substitution suggests these changes are due to functional modifications in normally existing connections. With the deafferentation conditions used in the present study, input substitution was limited to only parts of the deprived cortex. A hypothesis is presented which suggests these changes are due to adjustments in the dominance of saphenous and sciatic inputs to specific regions of cortex.
Neonatal 6-hydroxydopamine treatment eliminates cholinergic sympathetic innervation and induces sensory sprouting in rat sweat glands
Authors: Yodlowski ML , Fredieu JR , Landis SC
Published: March 2018

Previous studies of the development of cholinergic sympathetic innervation of sweat glands in rat footpads suggested that these terminals initially exhibit noradrenergic properties which are lost as the glands and their innervation mature. We have treated neonatal and adult rats with 6-hydroxydopamine (6-OHDA), a toxic congener of norepinephrine, and compared its effects on the cholinergic sympathetic innervation of sweat glands and the noradrenergic sympathetic innervation of the iris, salivary gland, and blood vessels. As reported by others, 6-OHDA treatment of neonates caused the destruction of noradrenergic fibers in the iris and salivary gland but did not affect other fibers projecting to these targets that stain for acetylcholinesterase (AChE). We found that 6-OHDA treatment of neonatal animals also caused the destruction of the sympathetic axons in immature sweat glands that possess catecholamine histofluorescence and tyrosine-hydroxylase-like immunoreactivity. Furthermore, when such animals were examined as adults, we found no AChE staining, vasoactive intestinal peptide (VIP)-like immunoreactivity, or characteristic sympathetic axonal varicosities. However, the denervated glands were invested by a plexus of sensory axons, some of which exhibited substance P-like immunoreactivity (SP-IR). An increase in the number of SP-IR fibers also occurred in the sympathetically denervated irides of these animals. Chronic treatment of neonates with guanethidine, another adrenergic sympathetic neurotoxin, resulted in similar loss of cholinergic sweat gland innervation. Treatment of adults rats with doses of 6-OHDA identical to those used to treat neonates caused the loss of noradrenergic fibers from the iris, salivary gland, and many blood vessels but did not noticeably affect AChE and VIP staining or axonal ultrastructure in the sweat glands. However, treatment with higher doses of 6-OHDA did cause significant axonal degeneration. The response of the sympathetic innervation of developing but not mature sweat glands to 6-OHDA provides evidence for a transition from noradrenergic to cholinergic phenotype during the development of sympathetic neurons in vivo similar to the transition observed in cell culture. The sprouting of sensory axons may be caused by NGF-like trophic influences present in some sympathetically denervated tissues.
Endoglycosidase H digestion of neuronal intracellular lectin-binding sites
Authors: Hart CE , Wood JG
Published: March 2018

Cerebellar Purkinje cells contain intracellular membrane systems that are highly enriched in concanavalin A (Con A)-binding sites and which may be involved in axonal and dendritic transport. We have attempted to characterize these Con A-binding sites in fixed slices of cerebellum by their susceptibility to endoglycosidase H (Endo H) digestion. Tissue slices labeled with Con A-peroxidase without prior Endo H digestion had moderately dense label in the molecular and granular layers with the heaviest label occurring in Purkinje cell somata. Endo H digestion of tissue slices produced little change in the pattern of Con A label in the molecular and granular layers, but the Con A label in Purkinje cell somata was removed except for small discrete patches. Electron microscopic examination of Purkinje cells from tissue slices not digested with Endo H showed Con A label in cisternal elements of the endoplasmic reticulum (ER), nuclear envelope, hypolemmal cisternae, and the Golgi complex. Presynaptic terminal smooth membrane cisternae and dendritic hypolemmal cisternae of Purkinje cells were also labeled with Con A-peroxidase. Endo H digestion removed Con A-binding sites in cisternae of the ER, somal and dendritic hypolemmal membrane system, and presynaptic terminal smooth membrane profiles. Con A-binding sites in the nuclear envelope and Golgi complexes of Purkinje cells were not removed by Endo H digestion. These results present ultrastructural evidence in support of biochemical studies which report the rough ER as the site of polymannose oligosaccharide addition to nascent polypeptides.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell death of motoneurons in the chick embryo spinal cord. IX. The loss of motoneurons following removal of afferent inputs
Authors: Okado N , Oppenheim RW
Published: March 2018

The primary aim of this study was to clarify the role of supraspinal, propriospinal, and primary sensory afferents in motoneuron (MN) development in the lateral motor column (LMC) of the lumbar spinal cord of the chick embryo. For this purpose three types of operations were carried out on embryonic day (E) 2. (1) The spinal cord was transected at the cervical (C-gap) or at the thoracic (T-gap) level so as to eliminate supraspinal and/or propriospinal inputs to the lumbar cord. (2) The entire lumbar neural crest was removed (NCR) in order to eliminate primary sensory inputs arising from the dorsal root ganglia (DRG). (3) A combined operation of T-gap and lumbar NCR was performed. The numbers of MNs in the LMC of the lumbar spinal cord were counted in embryos sacrificed between E10 and E18. The number of MNs on E10, when naturally occurring neuron death is almost complete, was not changed following either operation 1 or 2 described above. However, by E16, when naturally occurring neuron death is over, these same deafferented groups had 20 to 25% fewer MNs than did controls. Thus, the removal of either descending or sensory (DRG) afferents results in a significant increased loss of MNs that appears to take place only during the final stages of natural neuronal death or later. By contrast, the removal of both sources of input (T-gap + NCR) results in an additional 37% loss of MNs by E10 compared to controls. Thus, in this group deafferentation significantly increases cell loss during the major period of naturally occurring MN death (E5 to E10). No further loss of MNs occurs in this group after E10. Chronic treatment of deafferented embryos with curare from E6 to E9 or from E10 to E14 prevented the naturally occurring MN loss during these stages but was without effect on the increased cell loss induced by deafferentation. These results imply that the cellular mechanisms involved in target- versus afferent-regulated cell death are different. Collectively, these results indicate that the regulation of MN numbers is more complicated than previously thought. Both targets and afferents appear to be involved in controlling the survival of this population of neurons during the period of naturally occurring MN death.
A kinetic study of the in vivo incorporation of 65ZN into the rat hippocampus
Authors: Sato SM , Frazier JM , Goldberg AM
Published: March 2018

Previous autoradiographical studies utilizing 65Zn demonstrated an apparent concentration of 65Zn in the mossy fiber boutons of the hippocampus. To examine the speciation of the 65Zn pool found in this neuronal pathway, we investigated the in vivo incorporation of systemic 65Zn into rat hippocampus compared with other brain regions. We were especially interested in kinetically assessing the zinc associated with three previously identified cytosolic zinc-binding species found in the hippocampus. The hypothesis that two of these cytosolic zinc-binding species, a metallothionein-like protein and a putative zinc-glutathione complex, may be responsible for the sequestration of zinc in the hippocampus was tested. It was confirmed that the t 1/2 of hippocampal zinc is longer than other brain regions that were studied. Furthermore, we observed that 65Zn is incorporated into three cytosolic zinc-binding species in the hippocampus as resolved using Ultrogel AcA 34 gel permeation chromatography. One of these species, the putative zinc- glutathione complex, accumulates zinc more slowly than the other species. The data suggest that the putative zinc-glutathione complex may represent an important 65Zn pool in the hippocampus. This finding is in accordance with out hypothesis that a zinc-binding species, specifically, the putative zinc-glutathione complex, may be responsible for the sequestration of zinc in the hippocampal mossy boutons.
Uptake of nerve growth factor along peripheral and spinal axons of primary sensory neurons
Authors: Richardson PM , Riopelle RJ
Published: March 2018

To investigate the distribution of nerve growth factor (NGF) receptors on peripheral and central axons, [125I]NGF was injected into the sciatic nerve or spinal cord of adult rats. Accumulation of [125I]NGF in lumbar dorsal root ganglia was monitored by gamma emission counting and radioautography. [125I]NGF, injected endoneurially in small quantities, was taken into sensory axons by a saturable process and was transported retrogradely to their cell bodies at a maximal rate of 2.5 to 7.5 mm/hr. Because very little [125I]NGF reached peripheral terminals, the results were interpreted to indicate that receptors for NGF are present on nonterminal segments of sensory axons. The specificity and high affinity of NGF uptake were illustrated by observations that negligible amounts of gamma activity accumulated in lumbar dorsal root ganglia after comparable intraneural injection of [125I] cytochrome C or [125I]oxidized NGF. Similar techniques were used to demonstrate avid internalization and retrograde transport of [125I]NGF by intraspinal axons arising from dorsal root ganglia. Following injection of [125I]NGF into lumbar or cervical regions of the spinal cord, neuronal perikarya were clearly labeled in radioautographs of lumbar dorsal root ganglia. Sites for NGF uptake on primary sensory neurons in the adult rat are not restricted to peripheral axon terminals but are extensively distributed along both peripheral and central axons. Receptors on axons provide a mechanism whereby NGF supplied by glia could influence neuronal maintenance or axonal regeneration.
Physiological evidence for specificity of synaptic connections between individual sensory and motor neurons in the brachial spinal cord of the bullfrog
Authors: Lichtman JW , Frank E
Published: March 2018

We have studied synaptic connections between individual stretch- sensitive muscle afferents and motoneurons in the brachial spinal cord of bullfrogs. Sensory afferents from a given head of the triceps brachii muscle preferentially innervate motoneurons that project to the same muscle head. This preference is characterized in two ways: each class of sensory axon innervates a greater proportion of corresponding motoneurons than of motoneurons projecting to synergistic or unrelated muscles, and the synaptic potentials in these corresponding motoneurons are motoneurons that project to the same muscle head. This preference is characterized in two ways: each class of sensory axon innervates a greater proportion of corresponding motoneurons than of motoneurons projecting to synergistic or unrelated muscles, and the synaptic potentials in these corresponding motoneurons are of larger amplitude. A novel feature of these experiments is that even the smallest averaged synaptic potential is several times larger than the noise level. These smallest synaptic potentials thus represent the smallest synaptic interaction between a sensory and motor cell, and they could be the physiological correlate of a single sensory bouton on a motoneuronal dendrite.
Localization and characterization of vasopressin-binding sites in the amygdala of the rat brain
Authors: Dorsa DM , Petracca FM , Baskin DG , Cornett LE
Published: March 2018

Putative receptors for arginine-vasopressin (AVP) in rat brain were localized and characterized using autoradiographic and radioligand- binding techniques. When brain slices were incubated with tritium- labeled vasopressin, an intense concentration of binding sites was identified which included the medial aspects of the amygdala. Binding of labeled AVP to membrane preparations from this brain region was saturable, specific, reversible, and of high affinity. An antagonist of the peripheral pressor activity of vasopressin was found to be a potent competitor for binding to this site.
Segregation of stimulus phase and intensity coding in the cochlear nucleus of the barn owl
Authors: Sullivan WE , Konishi M
Published: March 2018

The cochlear nucleus of the barn owl is composed of two anatomically distinct subnuclei, n. magnocellularis (the magnocellular nucleus) and n. angularis (the angular nucleus). In the magnocellular nucleus, neurons tend to respond at a particular phase of a stimulus sine wave. Phase locking was observed for frequencies up to 9.0 kHz. The intensity- spike count functions of magnocellular units are characterized by high rates of spontaneous activity, a narrow range of intensities over which spike counts changed from spontaneous to saturation levels, and a small increase in spike counts with intensity over that range. In the angular nucleus, neurons showed little or no tendency to respond at a certain sinusoidal phase, although some showed weak phase locking for frequencies below 3.5 kHz. Angular units typically had low spontaneous rates, large dynamic ranges, and large increases in spike counts with intensity, resulting in high saturation levels. The clear difference between the two nuclei in sensitivity to both phase and intensity and the reciprocity in response properties support the hypothesis that each nucleus is specialized to process one parameter (phase or intensity) and not the other.
Routing of transmitter and other changes in fast axonal transport after transection of one branch of the bifurcate axon of an identified neuron
Authors: Aletta JM , Goldberg DJ
Published: March 2018

The regulation of the quantities and types of organelles that leave the neuronal cell body destined for use in the axon and its terminals is not well understood. We had previously found that transport of transmitter undergoes a precise down regulation when most of one branch of the bifurcate axon of an identified serotonergic neuron was removed. We have now investigated further the nature of the regulatory event and the reason for its initiation by eliminating portions of the axonal tree of this neuron. We find that the down regulation is more likely to be due to the loss of synapses than of axon because transport of [3H]serotonin decreases as much when an axonal branch is transected distally as after a proximal transection. Transport of [3H]fucosyl glycoprotein, which normally is associated with the serotonergic vesicle in this axon, decreases to the same extent as transport of [3H]serotonin following proximal transection. The glycoprotein down regulation occurs much more rapidly, possibly due to an inhibition of vesicle synthesis. A secondary rise in transport of [3H] fucosyl glycoprotein 3 days to 2 weeks after axotomy suggests that the radiolabeled glycoprotein has undergone a redistribution into organelles not normally labeled and transported in intact neurons in large amounts, since [3H]serotonin transport remains stably diminished during this period. We also describe here a case of routing of rapidly transported material. When one axonal branch is cut far from the point of bifurcation (approximately 10 mm), [3H]serotonin is directed away from the ranch lacking its synaptic terminals and into the remaining intact branch even though the transected branch is physically capable of transporting its normal amount of [3H]serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)
Glutamic acid decarboxylase-immunoreactive neurons and terminals in the lateral geniculate nucleus of the cat
Authors: Fitzpatrick D , Penny GR , Schmechel DE
Published: March 2018

We have examined the distribution of neurons and terminals that are immunoreactive for glutamic acid decarboxylase (GAD), the synthesizing enzyme for the inhibitory neurotransmitter gamma-aminobutyric acid within the lateral geniculate nucleus of the cat. We estimate that GAD- positive neurons constitute approximately one-fourth of the neurons in all layers of the lateral geniculate nucleus and in the medial interlaminar nucleus (MIN). In addition, almost all of the neurons within the perigeniculate nucleus are GAD-positive. The mean size of GAD-positive cell bodies is significantly smaller than the mean size of unlabeled neurons in all subdivisions of the lateral geniculate nucleus. GAD-positive neurons have thick primary dendrites which are associated with thin lightly immunoreactive processes that give rise to clusters of GAD-positive terminals. Clusters of GAD-positive terminals are prominent in lamina A, A1, magnocellular C, and MIN but are rare in the parvocellular C laminae. Within the A laminae, GAD immunoreactivity is found within vesicle-containing profiles of the synaptic glomerulus lying postsynaptic to optic axon terminals and presynaptic to unlabeled dendritic profiles. GAD-positive neurons in the A laminae are distinguished from other small to medium-sized neurons by their failure to label following injections of HRP into visual cortex and by their lack of cytoplasmic laminated body. These results support the idea that GAD-positive neurons constitute a distinct population of neurons in the lateral geniculate nucleus of the cat; a population which has a number of features in common with previous descriptions of presumed local circuit neurons based on Golgi staining.
Glia are a unique substrate for the in vitro growth of central nervous system neurons
Authors: Noble M , Fok-Seang J , Cohen J
Published: March 2018

We have examined the consequences of surface interactions with glial and nonglial cells on the in vitro growth of CNS neurons. When cerebellar or spinal cord cells were plated onto monolayers highly enriched in cortical astrocytes or sciatic nerve Schwann cells, neurons generally grew as single cells and showed relatively little tendency to aggregate. Similarly, neurites showed little tendency to fasciculate. In contrast, when plated onto fibroblast, heart muscle-fibroblast, or astrocyte-free meningeal monolayers, neurons rapidly aggregated, and neurite outgrowth was primarily in large fascicles. There were no glia detectable in the majority of aggregates or fascicles, suggesting that aggregation and fasciculation were due to interactions between neurons. Neurite outgrowth over 24 hr was also greater on astrocytes than on nonglia. Whether or not aggregation and fasciculation occurred was due to surface properties of the glial and nonglial cells. When neurons were added to astrocyte and nonglial monolayers growing in medium conditioned by a large excess of co-cultured nonglia or astrocytes, respectively, the pattern of neuronal growth was determined by the type of monolayer with which the neurons were in contact. Moreover, the initial growth of neurons on heat-killed astrocytes was indistinguishable from growth on living astrocytes. The pattern of neuronal growth on these different monolayers suggests that neurons are more adherent to glia than to other neurons but are more adherent to other neurons than to nonglia. Such an adherence hierarchy could explain the consistent finding of an apposition of neurons to glial surfaces during neuronal migration and axon outgrowth. Our findings also suggest that the interaction of axons with the non-neuronal milieu through which they grow may play an important role in regulating fasciculation, a process which has generally been treated as due primarily to axon-axon interactions.
Strengthening of synaptic contacts of an excitatory axon on elimination of a second excitatory axon innervating the same target
Authors: Parnas I , Dudel J , Cohen I , Franke C
Published: March 2018

In the deep abdominal extensor muscles of spiny lobsters (Panulirus- pennicillatus), the common excitor axon of segment II was eliminated by intracellular injection of pronase. At 1 to 23 days after the operation, the quantal content of excitatory postsynaptic currents (EPSCs), elicited by stimulation of the specific excitor of the L1 muscle, was determined in a specific area of the L1 muscle, both in the operated and in the contralateral control side. The EPSCs in the operated muscles had about a 5 times higher quantal content compared to those in the controls, the change developing within 1 to 2 days after operation. In camera lucida drawings of preparations stained with methylene blue, increased branching of the remaining excitatory axon was obvious at more than 4 days after the operation. To investigate the possibility of contribution of central mechanisms (Rotshenker, S. (1979) J. Physiol. (Lond.) 292: 535–547). to this effect, the bundle of five axons to the deep abdominal extensors of segment II was cut immediately after injection of pronase into the common excitor axon. This caused a reduction of the quantal content of EPSCs and shrinking of the field of innervation in the operated L1 muscle as compared to the control. Therefore, axonal continuity or central connections seem to be necessary for the development of an increased innervation by the specific excitor to L1 after eliminating the common excitor axon. Possible postsynaptic effects of the elimination of the common excitor axon were controlled by recording synaptic single channel currents elicited by the excitatory transmitter glutamate, using the patch clamp method. These single current events did not show appreciable changes in operated L1 muscles. Therefore, the presynaptic strengthening effect on the nerve terminals of the specific L1 excitor is predominant after elimination of the common excitor axon.
Characterization of the rat mutant dystonic (dt): a new animal model of dystonia musculorum deformans
Authors: Lorden JF , McKeon TW , Baker HJ , Cox N , Walkley SU
Published: March 2018

An inherited neurological disorder characterized by sustained twisting movements during waking has been discovered in Sprague-Dawley rats. The mutation follows an autosomal recessive pattern of inheritance and has been named dystonic (dt). The rat mutants are indistinguishable from normal littermates in open field behavior and climbing activity prior to postnatal days 9 to 10. Clinical signs begin to appear on day 10 and include twisting of the axial musculature, hyperflexion of the trunk, self-clasping of forelimbs and hindlimbs, and poor placement of the limbs during locomotion. No morphological lesions of neural or non- neural tissues have been observed with routine light microscopy. Dystonic rats demonstrate significantly elevated cerebellar norepinephrine levels, although levels in other terminal fields of the locus ceruleus are similar to those of normal littermates. No differences in the pattern or density of noradrenergic innervation were apparent in cerebellar tissue from dt rats examined with histochemical fluorescence techniques. These mutants were less sensitive than unaffected littermates to the akinesic effects of the dopamine blocker haloperidol. However, striatal dopamine levels were not reliably different from normal in dt rats, and their response to the movement- stimulating effects of apomorphine appeared normal. These findings suggest the presence of biochemical disturbances in the extrapyramidal system of dt rats. The dt rat may provide a useful model for human dystonia musculorum deformans.
Partial purification and functional identification of a calmodulin- activated, adenosine 5'-triphosphate-dependent calcium pump from synaptic plasma membranes
Authors: Papazian DM , Rahamimoff H , Goldin SM
Published: March 2018

Synaptic plasma membranes isolated from rat brain contain a calmodulin- activated Ca2+ pump. It has been purified 80- to 160-fold by solubilization with Triton X-100 and affinity chromatography on a calmodulin-Sepharose 4B column. After reconstitution into phospholipid vesicles, the affinity-purified pump efficiently catalyzed ATP dependent Ca2+ transport, which was activated 7- to 9-fold by calmodulin. The major protein component of the affinity-purified preparation had a Mr = 140,000; it was virtually the only band visualized on a Coomassie blue-stained SDS polyacrylamide gel. It has been identified as the Ca2+ pump by two functional criteria. First, it was phosphorylated by [gamma-32P]ATP in a Ca2+-dependent manner; the phosphorylated protein had the chemical reactivity of an acyl phosphate, characteristic of the phosphorylated intermediates of ion- transporting ATPases. Second, the protein was enriched by transport- specific fractionation, a density gradient procedure which uses the transport properties of the reconstituted Ca2+ pump as a physical tool for its purification. By analogy with calmodulin-activated (Ca2+ + Mg2+) ATPases of other cell types, and because of its presence in a synaptic plasma membrane fraction, we hypothesize that the calmodulin- activated Ca2+ pump functions in vivo to extrude Ca2+ from nerve terminals.
An electron microscopic study of the development of axons and dendrites by hippocampal neurons in culture. II. Synaptic relationships
Authors: Bartlett WP , Banker GA
Published: March 2018

We have studied by electron microscopy the synaptic relationships which develop between hippocampal neurons in dissociated cell cultures. Neurons, obtained from fetal rats at 18 to 20 days of gestation, were plated at high cell density onto polylysine-treated coverslips and maintained in serum-free medium. After 3 to 4 weeks, the cells were interconnected by an extensive network of processes which made frequent synaptic contacts with one another. Certain of the processes could be readily identified as dendrites by their branching pattern and content of polyribosomes. Often individual dendrites could be followed for 100 to 200 microns from their cells of origin. In every instance observed, the dendrites were postsynaptic. The presynaptic processes were quite different in appearance; they lacked ribosomes, their microtubules were spaced more closely together, and they were thinner than even the distal dendrites except at synaptic sites where they formed varicosities. Because of their small diameter, the presynaptic processes could not be traced through the dense neuropil to their origins, but in all other respects they resembled the axons identified in younger cultures. There were differences in the features of the synapses present on different portions of the cell. The great majority of synapses on dendritic spines made asymmetric junctions, whereas those on cell bodies made symmetric junctions. Both types were observed on dendritic shafts, but asymmetric junctions were predominant. These results show that synapses do not form indiscriminately between the processes which develop in culture, but rather that axons and dendrites acquire distinct synaptic polarities, just as when they develop in situ.
Cellular mechanisms for modulation of posture by octopamine and serotonin in the lobster
Authors: Harris-Warrick RM , Kravitz EA
Published: March 2018

Injection of the monoamines octopamine and serotonin into the hemolymph of lobsters causes them to assume opposing static postures: octopamine causes a tonic extension of all extremities, while serotonin induces a tonic flexion. These amines have been shown previously to act as circulating neurohormones and to cause contraction of isolated exoskeletal muscles. The opposing postures elicited by amine injection do not appear to arise from peripheral actions, however, since serotonin and octopamine have similar effects on both flexor and extensor muscles. Instead, the amines are present within the central nervous system where they are probably released synaptically to activate coordinated patterns of tonic motor activity generating the observed postures. These motor patterns have been recorded from abdominal ganglia and involve the synchronized activation and inhibition of multiple excitatory and inhibitory motoneurons innervating the postural flexor and extensor muscles. These effects can be observed in an isolated abdominal ganglion. To begin a search for the cellular targets of amine action within the central nervous system, we recorded from identified postural motoneurons in abdominal ganglia. In two motoneurons that act to produce postural extension, octopamine reduced and serotonin raised the apparent threshold for action potential generation recorded in the somata. The amines do not significantly affect the resting potential or input resistance of the motoneurons measured in the cell bodies. Although the amine effect on motoneuron excitability could be due to actions directly on the motoneurons, our evidence suggests that at least part of the effect results from activation or inhibition of premotor interneurons: (1) an increase in EPSP frequency is observed in the motoneurons during octopamine superfusion, while a small decrease is observed during serotonin superfusion; (2) the amine effects on action potential threshold are abolished by cobalt ion. These results suggest that octopamine and serotonin have dual effects on posture: within the central nervous system, they act specifically to generate coordinated motor patterns for flexion or extension; as circulating neurohormones, they act nonspecifically to enhance the responses of exoskeletal muscles to motoneuronal activation.
Neuropeptide proctolin in postural motoneurons of the crayfish
Authors: Bishop CA , Wine JJ , O'Shea M
Published: March 2018

The neuropeptide transmitter candidate proctolin (H-Arg-Tyr-Leu-Pro-Thr- OH) was associated with three of the five excitatory motoneurons innervating the tonic flexor muscles of the crayfish abdomen. Proctolin immunohistochemical staining occurred in cell bodies and axons of these three identified neurons. Stained axon terminals were detected across the entire tonic flexor muscle. Bioassay of extracts of the tonic flexor muscles indicated the presence of 370 fmol of proctolin/muscle or 670 fmol/mg dry weight. Bioactivity was eliminated in muscles in which the tonic flexor motor root was cut 2 months prior to extraction and in muscle extracts pre-incubated with proctolin antiserum. High pressure liquid chromatography purification of tissue extract indicated that all bioactivity in the crude extract was due to authentic proctolin. Our findings suggest that these three cells function as peptidergic motoneurons. A precedent for this is the proctolin- containing postural motoneuron of the cockroach.
Sympathetic reinnervation of the pineal gland after postganglionic nerve lesion does not restore normal pineal function
Authors: Bowers CW , Baldwin C , Zigmond RE
Published: March 2018

The activity of the enzyme serotonin N-acetyltransferase (NAT) in the rat pineal gland exhibits a large circadian rhythm, with peak activity occurring at night. This rhythm is dependent on stimulation of the pineal gland by neurons whose cell bodies are in the superior cervical ganglia and whose axons reach the gland via the internal carotid nerves (ICNs). Two days after both ICN were cut, crushed, or frozen, nighttime NAT activity was decreased by 90%. The remaining low level of enzyme activity was not affected by decentralization of the superior cervical ganglia. Thus, this enzyme activity did not depend on the activity of neurons in these ganglia. Bilaterally lesioning the ICN also abolished the neuronal uptake of norepinephrine in the pineal, further indicating that the sympathetic innervation of the gland had been destroyed. Three months after crushing both ICNs, nighttime NAT activity was only 20% of control values. However, in these animals, bilateral decentralization of the superior cervical ganglion reduced this low level of NAT activity by 90%. Thus, NAT activity, although low, was again dependent on sympathetic nerve stimulation. In contrast to this rather small recovery of nocturnal NAT activity, the norepinephrine uptake capacity of the gland recovered to 60% of control values. A similar discrepancy between the extent of recovery of NAT activity and of norepinephrine uptake was observed when the ICNs were frozen rather than crushed. To determine to what extent the sympathetic nerves that had reinnervated the pineal gland in these lesioned animals were capable of regulating NAT activity, their cervical sympathetic trunks were stimulated electrically at 5 Hz for 3 hr during the daytime.(ABSTRACT TRUNCATED AT 250 WORDS)