bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of choroid and ciliary neurons in the avian ciliary ganglion and evidence for substance P as a neurotransmitter
Authors: Dryer SE , Chiappinelli VA
Published: March 2018

Intracellular recordings were made from identified choroid and ciliary neurons in the ciliary ganglion of the embryonic chick. Choroid neurons, which were innervated by multiple preganglionic fibers, frequently displayed noncholinergic slow excitatory postsynaptic potentials (EPSPs) following repetitive stimulation of the preganglionic nerve trunk. These slow potentials were blocked by high Mg2+/low Ca2+ buffer and were closely mimicked by bath application of substance P, which is known to be present within both populations of preganglionic nerve terminals. Substance P-induced depolarizations desensitized during prolonged exposure, at which time it was no longer possible to evoke slow synaptic potentials. Following manual voltage clamp to resting membrane potential, parallel increases in input resistance were seen during the slow EPSP and the response to substance P, suggesting that the two responses share common mechanisms. Ciliary neurons, which were innervated by a single preganglionic fiber and displayed dual electrical-chemical synapses, did not exhibit slow synaptic potentials and were unaffected by bath application of substance P. The magnitude and time course of fast nicotinic EPSPs elicited in ciliary neurons by 0.5 Hz presynaptic stimulation were also unchanged in the presence of 1 to 3 microM substance P. Although the ciliary and choroid neurons share a common embryological origin in the neural crest, they are specialized for quite different physiological roles. Integration of multiple presynaptic inputs occurs at choroid synapses, mediated by the presence of both subthreshold fast nicotinic EPSPs and the slow EPSP. In contrast, synapses on ciliary neurons have specializations which preclude any integrative function, including single innervation, a high quantal content, electrical coupling potentials, and a lack of slow synaptic potentials.
Synaptic plasticity in the molluscan peripheral nervous system: physiology and role for peptides
Authors: Coates CJ , Bulloch AG
Published: March 2018

The plasticity of a synapse in the molluscan peripheral nervous system was examined under a variety of experimental, physiological, and pharmacological conditions. These studies employed the isolated salivary glands and attached buccal ganglia of the freshwater snail Helisoma. Action potentials evoked in buccal neuron 4 normally evoke a large excitatory postsynaptic potential (EPSP) which drives an action potential in gland secretory cells. In order to measure modulation of the EPSP, action potential generation in gland cells was prevented by bathing the preparation in low calcium, high magnesium salines. The relationship between the gland EPSP amplitude and specific physiological properties of neuron 4 was analyzed. In common with some central molluscan synapses, the EPSP was found to be strongly influenced by the membrane potential of neuron 4. Specifically, its amplitude was reduced by hyperpolarization of the neuron 4 soma. The relationship between EPSP amplitude and somatic potential of neuron 4 was linear in the range from resting potential (-47 +/- 6mV) to -100 mV. Furthermore, the EPSP amplitude was directly proportional to the action potential half-width of neuron 4. In order to evaluate the possible physiological role of this action potential/EPSP relationship, we examined whether gland EPSPs are modulated during the spike broadening that occurs in both spontaneous burst activity and imposed impulse trains. The preceding action potential/EPSP relationship was maintained under both of these conditions, i.e., EPSP magnitude increased as spikes broadened during bursts or trains. The peptidergic modulation of neuroglandular transmission was also examined. The molluscan peptide SCPB was found to depolarize neuron 4 and an increase in EPSP amplitude was concomitantly observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Evidence for a presynaptic adenylate cyclase system facilitating [3H]norepinephrine release from rat brain neocortex slices and synaptosomes
Authors: Schoffelmeer AN , Hogenboom F , Mulder AH
Published: March 2018

The effects of drugs known to enhance intracellular cyclic AMP levels on depolarization-induced [3H]norepinephrine release from superfused rat neocortical slices and synaptosomes were investigated. The adenylate cyclase activator forskolin, the membrane-permeating cyclic AMP analogues 8-bromo-cyclic AMP and dibutyryl cyclic AMP, as well as the phosphodiesterase inhibitors isobutylmethylxanthine and 4-(3- cyclopentyloxy-4-methoxyphenyl)-2-pyrolidone (ZK 62771) enhanced the electrically evoked release of [3H]norepinephrine from superfused rat brain neocortex slices. 8-Bromo-cyclic GMP was without effect on the electrically evoked release. When [3H]norepinephrine release was enhanced by prolonging the electrical pulse duration from 2 msec to 10 msec, the relative inhibitory effect of the Ca2+ channel blocker Cd2+ and the relative facilitatory effect of the K+ channel blocker 4- aminopyridine remained unaffected. In striking contrast, the relative facilitatory effects of forskolin and 8-bromo-cyclic AMP were strongly reduced, whereas the effect of ZK 62771 was almost doubled. When veratrine-induced release of [3H]norepinephrine from cortex synaptosomes was examined, the facilitatory effects of forskolin, 8- bromo-cyclic AMP, and ZK 62771 were even more pronounced than in brain slices. The data strongly support the hypothesis that a presynaptic adenylate cyclase system plays a facilitatory role in the stimulus- secretion coupling process in central noradrenergic nerve terminals.
gamma-Aminobutyric acid and benzodiazepine receptors in the kindling model of epilepsy: a quantitative radiohistochemical study
Authors: Shin C , Pedersen HB , McNamara JO
Published: March 2018

Quantitative radiohistochemistry was utilized to study alterations of gamma-aminobutyric acid (GABA) and benzodiazepine receptors in the kindling model of epilepsy. The radioligands used for GABA and benzodiazepine receptors were [3H] muscimol and [3H]flunitrazepam, respectively. GABA receptor binding was increased by 22% in fascia dentata of the hippocampal formation but not in neocortex or substantia nigra of kindled rats. Within fascia dentata, GABA receptor binding was increased to an equivalent extent in stratum granulosum and throughout stratum moleculare; no increase was found in dentate hilus or stratum lacunosummoleculare or stratum radiatum of CA1. The increased binding was present at 24 hr but not at 28 days after the last kindled seizure. The direction, anatomic distribution, and time course of the increased GABA receptor binding were paralleled by increased benzodiazepine receptor binding. Unexpectedly, GABA receptor-mediated enhancement of benzodiazepine receptor binding was slightly attenuated in fascia dentata of kindled compared to control rats. The anatomic distribution of the increased GABA receptor binding is consistent with a localization to somata and dendritic trees of dentate granule cells. We suggest that increased GABA and benzodiazepine receptor binding may contribute to enhanced inhibition of dentate granule cells demonstrated electrophysiologically in kindled animals.
Morphology and physiology of single neurons in the medial interlaminar nucleus of the cat's lateral geniculate nucleus
Authors: Raczkowski D , Sherman SM
Published: March 2018

Physiological studies have shown that the cat's retinogeniculocortical system is comprised of at least three parallel and independent pathways, the W-, X-, and Y-cell pathways. The morphological correlates of the constituent W-, X-, and Y-cells have been determined both in the retina and in the A and C laminae of the lateral geniculate nucleus. The aim of this study was to extend these structure/function relationships to neurons in laminae 1 and 2 of the medial interlaminar nucleus (MIN), which is a division of the cat's dorsal lateral geniculate nucleus. We used intracellular injection of horseradish peroxidase (HRP) into individual, physiologically identified MIN neurons. Since this procedure may yield an unrepresentative sample of MIN neurons, two controls were performed. First Nissl staining showed that the soma sizes of intracellularly labeled cells were representative of those of all MIN cells. Second, retrograde labeling following HRP injections into the optic radiations or specific visual cortical areas showed that the intracellularly labeled MIN cells were representative of MIN relay neurons. Many of the retrogradely labeled cells were so well filled that their entire dendritic arbors were revealed. Of 70 MIN neurons recorded physiologically, 22 were injected with HRP and successfully recovered. We also completely labeled the somata and dendrites of 114 MIN neurons from HRP injections into the optic radiations and retrogradely labeled 165 MIN neurons by injection of HRP into visual cortical areas. Our sample of intracellularly injected neurons, which were all Y-cells, were morphologically representative of all MIN relay cells. We thus conclude that laminae 1 and 2 of the MIN contain a nearly homogeneous population of Y-cells with properties essentially identical to those of Y-cells in the A and C laminae of the lateral geniculate nucleus. When viewed in the coronal plane, MIN projection neurons typically exhibited oval or elongated somata. In the medial and ventral parts of the MIN, these somata were smaller and more flattened. MIN soma sizes extended over the full range of those seen in the A laminae. Dendritic arbors of most MIN relay neurons radiated in a fairly spherical fashion. In the medial and ventral parts of the MIN, however, dendrites were oriented in a more bipolar fashion, but intermediate forms between spherical and bipolar arbors were also common. Dendrites of MIN projection neurons were typically smooth; most primary dendrites were straight, but secondary dendrites were more variable in structure.(ABSTRACT TRUNCATED AT 400 WORDS)
Parasympathetic, sympathetic, and sensory interactions in the iris: nerve growth factor regulates cholinergic ciliary ganglion innervation in vivo
Authors: Kessler JA
Published: March 2018

Interactions between peptidergic sensory nerves, noradrenergic sympathetic nerves, and cholinergic parasympathetic fibers were examined in the rat iris. The putative peptide neurotransmitter, substance P (SP), was used as an index of the trigeminal sensory innervation, tyrosine hydroxylase (TH) activity served to monitor the sympathetic fibers, and choline acetyltransferase (CAT) activity was used as an index of the parasympathetic innervation. Destruction of the sympathetic innervation by neonatal administration of 6-hydroxydopamine resulted in increased SP development and a smaller increase in CAT activity in the iris. Moreover, trigeminal ablation resulted in an increase in both TH and CAT activities. Finally, ciliary ganglionectomy resulted in increased SP and a smaller increase in TH activity in the iris. Administration of nerve growth factor (NGF) into the anterior chamber substantially increased both SP and TH activity in the iris and also increased CAT activity to a lesser extent. Moreover, administration of anti-NGF into the anterior chamber prevented both the sympathectomy-induced increases in SP and CAT, and the increases in TH and CAT activities after trigeminal ablation, suggesting that NGF mediated these increases. These observations suggest that the sympathetic, sensory, and parasympathetic innervations of the iris interact by altering availability of NGF elaborated by the iris. Regulation of iris CAT activity was examined in greater detail. Injection of the cholinergic toxin, AF64A, into the anterior chamber concurrently with ablation of the sympathetic and sensory innervations paradoxically increased CAT activity, whereas AF64A alone decreased CAT activity.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of cholecystokinin on the in vivo release of newly synthesized [3H]dopamine from the nucleus accumbens of the rat
Authors: Voigt MM , Wang RY , Westfall TC
Published: March 2018

It has been reported that in the medial nucleus accumbens (NAc) there are nerve terminals which contain either the neuropeptide cholecystokinin (CCK) or the catecholamine dopamine (DA), as well as terminals which contain both. In this study, we have examined the action of CCK-peptides on the basal and potassium-evoked release of [3H]DA within this structure. The in vivo release of [3H]DA, newly synthesized from [3H]tyrosine, was measured by using the push-pull cannula perfusion technique. It appeared that a large percentage of the [3H]DA released under resting conditions was dependent upon nerve impulse activity as it was found that tetrodotoxin, absence of extracellular Ca2+, and the inhibition of DA synthesis by alpha-methyl- p-tyrosine all decreased [3H]DA release by more than 50%. In addition, the potassium-evoked release of [3H]DA was found to be almost completely dependent upon extracellular Ca2+. When sulfated CCK- octapeptide was administered into the NAc, it was found to increase the basal levels of [3H]DA released at concentrations of 2 X 10(-8) and 2 X 10(-7) M. However, at 2 X 10(-6) M there was no longer an effect by this peptide. The unsulfated form was found to have no effect at a concentration which was maximally effective for the sulfated form. In contrast to its effects on the basal release of [3H]DA, sulfated CCK- octapeptide was found to attenuate the potassium-evoked release of [3H]DA from the NAc in a concentration-dependent fashion from 2 X 10(- 9) to 2 X 10(-6) M. The unsulfated form of the octapeptide had no effect on evoked release. Our results suggest that CCK acts to modulate the release of DA within the NAc in vivo in a complex manner, as it appears that the action of CCK depends not only on the concentration tested but also on the excitation state of the tissue during the testing period.
Topography of cytochrome oxidase activity in owl monkey cortex
Authors: Tootell RB , Hamilton SL , Silverman MS
Published: March 2018

In primate cortical tissue which has been stained for the mitochondrial enzyme cytochrome oxidase, a topographical pattern of regularly spaced blobs has been demonstrated in primary visual cortex (Hendrickson, A. E., S. P. Hunt, and J. -Y. Wu (1981) Nature 292: 605–607; Horton, J. C., and D. H. Hubel (1981) Nature 292: 762–764), and a pattern of stripes has been shown in secondary visual cortex (V2) as well (Livingstone, M. S., and D. H. Hubel (1982) Proc. Natl. Acad. Sci. U. S. A. 79: 6098–6101; Tootell, R. B. H., M. S. Silverman, E. Switkes, and R. L. De Valois (1982) Soc. Neurosci. Abstr. 8: 707). These regular cytoarchitectonic landmarks have proven extremely useful in parsing the functional and anatomical architecture of these two cortical areas. In order to look for similar landmarks in other cortical areas of a primate, we completely unfolded the cortical gray matter in the owl monkey (Aotus trivirgatus), sectioned it parallel with the flattened cortical surface, and stained the tissue for cytochrome oxidase. Distinctive cytochrome oxidase topographies were found in about seven different cortical areas. As in other primates, area V1 is characterized by blobs and area V2 is characterized by strips. In the owl monkey, area MT is characterized by an elaborate topography of dark staining in layers 1 to 4, interspersed with light blob-shaped regions, and partially surrounded by a dark ring. Many of these topographic inhomogeneities are also reflected in the lower layer myelination topography in MT. Visual area(s) VP/VA is characterized by an irregular or strip-like topography. In some animals, a distinctive topography can be seen in area DX, which is presumably equivalent to either area DM or DI. Primary auditory cortex stains very darkly, but the overall shape of area A is quite variable and the borders are indistinct. Somatosensory area 3B stains quite darkly with sharp borders, but again the overall shape of area 3B is different from that previously described.
Quantitative morphology and regional and laminar distributions of senile plaques in Alzheimer's disease
Authors: Rogers J , Morrison JH
Published: March 2018

Senile (neuritic) plaques are one of the two major neuropathologic hallmarks of Alzheimer's disease. Despite their obvious importance (e.g., they are significantly correlated with severity of dementia), there is little present information about their etiology, the specific neuronal elements that form them, or a quantitative definition of where in cortex they occur. We have sought clues to these issues by quantifying regional and laminar distributions of neocortical plaques and setting these data against the present wealth of information on neocortical cytoarchitecture and neurotransmitter-specific circuitry. Senile plaques are significantly more numerous in associative regions of neocortex than in sensory areas and are significantly more numerous in cortical laminae dominated by their role in corticocortical, associative relations. Plaques are also largest in those laminae characterized by large pyramidal cells subserving input/output functions. The quantitative distribution of senile plaques in Alzheimer's disease does not necessarily correspond to innervation patterns for any known subcortical afferent system. This, coupled with the finding that several different neurotransmitters can be immunocytochemically co-localized with plaques, casts doubts on a primary role of cholinergic deterioration in plaque etiology, and opens the possibility that neocortical senile plaques may derive from pathologic events initiated in the neocortex.
A double-labeling investigation of the afferent connectivity to cortical areas V1 and V2 of the macaque monkey
Authors: Kennedy H , Bullier J
Published: March 2018

The afferent connectivity of areas V1 and V2 was investigated using the fluorescent dyes fast blue and diamidino yellow. Simultaneous injection of each dye in retinotopically corresponding regions of these areas gave rise to two afferent populations of labeled neurons in subcortical and cortical structures which project to both areas. These two populations showed a variable degree of overlap in their spatial distribution. Neurons labeled by both dyes (double-labeled neurons) which, therefore, project to both areas, were found in substantial numbers in these overlap zones. When the injections were made in non- retinotopically corresponding regions in the two areas, both populations of labeled cells overlapped extensively in the cortex but not in subcortical structures, suggesting that the laws governing the topography of these two types of connections are different. In the cortex, the labeled neurons extended from the fundus of the lunate sulcus to the fundus of the superior temporal sulcus. A few labeled neurons were also found in the inferior temporal cortex and the parahippocampal gyrus. In all cortical regions, corticocortical neurons projecting to V1 and V2 were found in both supra- and infragranular layers, although double-labeled neurons were more numerous in infragranular layers. With increasing distance from V1 there was an increase in the proportion of neurons labeled in infragranular layers. The comparative strength of input to V1 and V2 was computed and was found to be higher to V2 in all cortical regions except the superior temporal sulcus which projected equally heavily to both areas. The superior temporal sulcus also stood out in that of all cortical regions it contained the highest proportion of double-labeled neurons. Single- and double-labeled neurons were found in a number of subcortical structures including the lateral geniculate nucleus, the inferior and lateral pulvinar, the intralaminar nuclei, the nucleus basalis of Meynert, and the amygdala. The pattern of labeling in the lateral pulvinar was in agreement with the suggestion that this structure has a complex topographical organization containing at least a dual representation of the visual field (Bender, D. B. (1981) J. Neurophysiol. 46: 672–693). In the pulvinar complex, densities of labeled neurons permitted evaluation of the strength of input to V1 and V2, the latter being the strongest. These results demonstrate that areas V1 and V2 share a vast amount of common input from the same cortical and subcortical structures and that a number of neurons project to both areas via branching axons.
Synaptogenesis by single identified neurons in vitro: contribution of rapidly transported and newly synthesized proteins
Authors: Ambron RT , Den H , Schacher S
Published: March 2018

The object of these studies is to define the molecular events that occur during synaptogenesis. Our approach is to use single identified Aplysia neurons grown in culture under conditions where chemical synapses are formed. In this report we studied synapses established by R2, a giant cholinergic neuron, onto neurons R15 and L11, and a group of left upper quadrant (LUQ) cells. The detailed electrophysiology of these contacts was described in the preceding paper (Schacher, S., S. G. Rayport, and R. T. Ambron (1985) (J. Neurosci. 5: 2851–2856). Within the animal, R2 synapses on thousands of unicellular mucus glands in the skin. R2 growing in vitro will establish contacts with isolated mucus glands. Although we do not know whether a functional synapse is formed, electron microscopy shows that the membrane in the area of contact is differentiated and that the ending is filled with various types of vesicles. A single R2 regenerating neurites in vitro synthesizes more than 300 polypeptides containing [35S]methionine. Many of these are subsequently transported into the growing neurites. We compared the newly synthesized proteins made by R2 before and after synapse formation and found that the expression of a 68-kilodalton (kd) and 72- kd protein was markedly enhanced after synaptogenesis. The finding that only two proteins were affected implies that many of the proteins required for synapse formation are present in R2 prior to contacting a target cell. Support for this idea was obtained when we compared the proteins present in R2's neurites in vitro with those that are rapidly transported to R2's mature synapses in vivo (Ambron, R. T., S. Schacher, and S. G. Rayport (1985) J. Neurosci. 5: 2866–2873).(ABSTRACT TRUNCATED AT 250 WORDS)
Correlations between the structural and functional characteristics of neurons in the superficial laminae and the hamster's superior colliculus
Authors: Mooney RD , Klein BG , Rhoades RW
Published: March 2018

Intracellular recording, receptive field mapping, and horseradish peroxidase (HRP) injection techniques were used to determine the structural and functional characteristics of neurons in the superficial laminae (stratum griseum superficiale and stratum opticum) of the hamster's superior colliculus (SC). Fifty-nine neurons (from 38 different hamsters) were successfully characterized, injected with HRP, and recovered. Of these, 8 were marginal cells, 14 had stellate morphology, 10 had narrow, vertically oriented dendritic trees, 12 had wide, vertically oriented dendritic arbors, and 8 were horizontal cells. Seven neurons had somatodendritic morphologies which did not fall into any of these groups. Overall, the distribution of receptive field properties for these cells matched that obtained in previous extracellular recordings from the superficial SC laminae in this species (Chalupa, L.M., and R.W. Rhoades (1977) J. Physiol. (Lond.) 270: 595–626; Chalupa, L.M. and R.W. Rhoades (1978) J. Physiol. (Lond.) 274: 571–592). There were significant correlations between receptive field properties and morphology. Sixty-four percent of the stellate cells and 75% of the marginal cells were directionally selective. Only 17% of the other cell types exhibited this response property. In addition, only 36% of the stellate cells and 25% of the marginal neurons were discharged by stationary, flashed spots. Eighty-one percent of the other recovered cells gave reliable responses to such stimuli. Stellate and marginal cells could also be differentiated from the other cell types on the basis of speed selectivity. Only 29% of the stellate and 13% of the marginal cells responded to stimulus speeds in excess of 20 degrees/sec.(ABSTRACT TRUNCATED AT 250 WORDS)
Opiate and alpha 2-adrenoceptor responses of rat amygdaloid neurons: co- localization and interactions during withdrawal
Authors: Freedman JE , Aghajanian GK
Published: March 2018

Interactions between neuronal responses mediated by opiate receptors and by alpha 2-adrenoceptors were characterized in the amygdala. Extracellular single-unit recordings and microiontophoresis were performed using five-barrel microelectrodes in chloral hydrate- anesthetized rats. A subpopulation of amygdaloid cells displayed inhibitory responses to morphine or D-Ala,D-Leu-enkephalin; antagonist studies suggested that both mu- and delta-opiate receptor subtypes were present. The same neurons displayed inhibitory responses to norepinephrine or clonidine mediated by alpha 2-adrenoceptors. Responses mediated by opiate receptors and by alpha 2-adrenoceptors were highly co-localized to the same subpopulation of amygdaloid neurons. Such cells responded to microiontophoresis of either morphine or clonidine, whereas other cells in the amygdala generally showed neither response. Responsive cells were characterized by a distinctive, triphasic waveform and a high sensitivity to glutamate. These cells were largely restricted to the nucleus centralis and the posterior portion of the nucleus medialis. Cells outside of this group showed suppressant responses to norepinephrine which appeared not to be mediated by alpha 2-adrenoceptors. After chronic morphine treatment, application of opioid antagonists elicited a withdrawal response, consisting of an increase in firing rate. Clonidine reversed the withdrawal response of these cells. The amygdala may be one of the regions of the nervous system in which clonidine acts to reduce symptoms of opiate withdrawal.
Neurofilament protein abnormalities in PC12 cells: comparison with neurofilament proteins of normal cultured rat sympathetic neurons
Authors: Lee VM
Published: March 2018

The studies described here characterize abnormalities in the expression of neurofilament (NF) proteins in a clonal rat pheochromocytoma (PC12) cell line as compared with normal NF proteins in cultured rat sympathetic neurons (RSNs). Cytoskeletal extracts from PC12 cells grown in the presence (PC12+ cells) or absence (PC12- cells) of nerve growth factor (NGF) and from RSNs grown in the presence of NGF were analyzed in nitrocellulose replicas of one- and two-dimensional polyacrylamide gels by the immunoblot method using monoclonal antibodies and antiserum to individual NF subunits. RSNs failed to express the high molecular weight NF subunit (NF200) for the first 10 days in culture although both lower molecular weight NF subunits (NF68 and NF150) were expressed by these cells. At later times in culture, all three NF subunits were present in immunoblots of RSNs. The immunoblot profile of NF proteins in PC12- cells was identical to that of RSNs grown in culture for up to 10 days. Growth of PC12 cells in NGF for up to 3 weeks did not alter this immunoblot profile except that no immunoband corresponding in NF200 was seen and the immunobands corresponding to NF68 and NF150 became more prominent. These data suggest that abnormalities in NF protein expression in PC12 cells are due to a paucity of NF200 or to the presence of immunochemically altered NF200. PC12 cells are an attractive model system for probing abnormal NF metabolism.
Cells born in adult canary forebrain are local interneurons
Authors: Paton JA , O'Loughlin BE , Nottebohm F
Published: March 2018

Thymidine autoradiography and retrograde transport of horseradish peroxidase (HRP) were combined to determine the connectivity of neurons born in adult canary forebrain. Adult male and female canaries were pretreated with [3H]thymidine to label cells undergoing DNA synthesis prior to mitosis. Thirty or 60 days later, neurons in a forebrain nucleus, hyperstriatium ventralis, pars caudalis (HVc), were labeled by retrograde transport of HRP injected into the only two nuclei known to receive a projection from HVc: robustus archistriatalis (RA) and area X of lobus parolfactorius. The birds were then killed and brain sections were treated to visualize cells containing HRP; these sections were processed for autoradiography to detect [3H]thymidine-labeled cells in the same tissue. More than 9% of all neurons in HVc were thymidine labeled; but of the almost 20,000 HRP-labeled projection neurons examined, fewer than 20 (0.1%) were labeled by the thymidine treatment. Furthermore, the median cell body size for area X-projecting cells was significantly larger than that of thymidine-labeled cells, and the median size of thymidine-labeled cells was significantly larger than that of RA-projecting cells. The simplest interpretation of these results is that the new neurons incorporated into nucleus HVc in adult canary brain are local interneurons, intermediate in size between neurons projecting to RA and area X.
The neuronal endomembrane system. II. The multiple forms of the Golgi apparatus cis element
Authors: Lindsey JD , Ellisman MH
Published: March 2018

The cis element and its associated tubules and vesicles are ideally positioned to play a major role in the sorting of rough endoplasmic reticulum components destined for processing in the Golgi apparatus. Its position is also ideal for playing a major role in the assembly of the saccules which constitute the Golgi apparatus. The present study was undertaken to critically analyze the normal morphology of this Golgi apparatus component. Seventy- to 2000-nm-thick sections of bullfrog spinal ganglia, fixed by osmium impregnation as well as by conventional protocols, were studied using standard and high voltage electron microscopy. Impregnated cis elements were also reconstructed from 170-nm serial sections. These studies found that adjacent neurons within the given ganglion contain cis elements of widely different morphology. In larger neurons, a different cis element organization was also found in different regions of the same cells. Based on structural comparisons, all of the different cis element forms observed could be systematically assembled into a gradual continuum of morphological variation. This continuum was circular in a manner analogous to chromosomal variations seen in highly mitotic tissues. For the sake of discussion, five distinctly different form categories were established. Some forms contained structures that are described herein for the first time. Most notable among these is the cis tubular network, an extensive system of parallel tubules that closely apposed the regularly perforated cis saccule. Osmiophilic vesicles were found to collect in tight clusters that closely apposed certain forms of the cis element. These findings raise the possibility that the cis element and its associated structures may undergo morphological transformations as part of their normal function.
The neuronal endomembrane system. III. The origins of the axoplasmic reticulum and discrete axonal cisternae at the axon hillock
Authors: Lindsey JD , Ellisman MH
Published: March 2018

The axoplasmic reticulum (AR) and the discrete element (e.g., vesicles, vesiculotubular bodies, multivesicular bodies, etc.) constitute the endomembrane system of the axon. It is reported here that the AR of bullfrog sciatic nerve readily fills with osmium deposits during osmium impregnation. In contrast, the discrete elements and mitochondria are highly resistant to impregnation. Hence this preparation is well suited to address the nature of possible interactions between AR and rough endoplasmic reticulum (RER) in the axon hillock. It is also ideal to study the origin of the axonal discrete elements within the cell body as well as their interaction with other somal endomembrane system components. Tissues used in the present study were spinal ganglia, sciatic nerve, and spinal roots from Rana catesbeiana. Thick sections (1 to 2 microm) of this material were studied by high voltage electron microscopy. In some cases, osmium impregnation was followed by en bloc staining with lead aspartate. This made visible membranous structures that had not filled with osmium deposits during impregnation. Serial 170-nm-thick sections of this latter material were prepared and serial stereo pair electron micrographs of axon hillocks were collected. These were used to reconstruct three-dimensionally the AR and to study its relationship with RER and with discrete elements. The impregnated AR within the axon hillock was found to terminate as many proximally pointing finger-like projections. A large portion of these projections were found to form connections with RER. Some, however, terminated as true blind endings. Single unimpregnated discrete cisternae were found throughout the cytoplasm of the cell body, axon hillock, and axon. Large clusters of unimpregnated vesicles were usually found in close association with the trans face of the Golgi apparatus. These results indirectly support the hypothesis that vectors of fast axonal transport, namely the discrete elements, form directly at the trans face of the Golgi apparatus. From here they move toward and subsequently down the axon without any membrane fission-fusion events with either RER or AR. AR, although it forms continuities with RER, retains a distinctly different chemical composition from RER as evidenced by its much higher affinity for osmium. Thus, it should be considered as an endomembrane component separate from, although intimately related to the RER.
Beta-receptor-stimulated and cyclic adenosine 3',5'-monophosphate- mediated taurine release from LRM55 glial cells
Authors: Madelian V , Martin DL , Lepore R , Perrone M , Shain W
Published: March 2018

Adrenergic stimulation of LRM55 glial cells results in the release of the neuroactive amino acid taurine. The present study characterizes the receptors involved in taurine release and shows that taurine release is mediated by cyclic adenosine 3′,5′-monophosphate (cAMP). beta-Receptors in LRM55 cells were first characterized by [125I]iodohydroxybenzylpindolol binding. Binding was stereospecific and saturable with time and ligand concentration. Kinetic analysis of equilibrium binding at 37 degrees C revealed a single component of high affinity (Km = 113 pm; Bmax = 52.1 +/- 5.0 fmol/mg of protein). The pharmacologies of the stimulation of cAMP accumulation and taurine release were similar. The agonists isoproterenol (IPR), epinephrine (E) and norepinephrine (NE) showed a rank order of potency characteristic of a beta-adrenergic system (IPR greater than E greater than or equal to NE). The beta-antagonists alprenolol and propranolol inhibited the IPR stimulation of both processes; the alpha-antagonist phentolamine did not. The dependence of taurine release on cAMP was further suggested by the similarity of the two time courses and was demonstrated by the stimulation of taurine release by the cAMP analogue dibutyryl cAMP. Thus, one physiological response of glial cells to beta- adrenergic stimulation is the release of taurine. Receptor-activated release of taurine from glia represents a previously undescribed neuronal-glial interaction by which glia may actively regulate neuronal excitability.
Map formation in the developing Xenopus retinotectal system: an examination of ganglion cell terminal arborizations
Authors: Sakaguchi DS , Murphey RK
Published: March 2018

Single axonal arbors of retinal ganglion cells have been stained by injecting cobalt extracellularly into the retinae of Xenopus embryos and tadpoles. The axonal endings of the earliest retinal axons to arrive in the midbrain were usually simple in appearance, often ended in growth cones, and terminated in tectal regions appropriate to their location in the eye. Thus, a topographic projection exists very early in the development (stages 37 to 39) of the projection, before the elaboration of complex axonal arbors. Retinal axons began acquiring more mature features, exemplified by the elaboration of terminal arbors, by stage 39. The arbors of most ganglion cells were elongated in the rostral-to-caudal dimension during early larval life (stages 40 to 45) and covered a large portion of tectal neuropil. During mid- larval stages (stages 46 to 50), arbors covered a relatively smaller proportion of the tectal neuropil. A quantitative analysis of this change suggests that the apparent decrease in size of the arbors, with respect to the tectum, is due to rapid growth of tectal neuropil and not due to retraction of an initially diffuse arbor. Thus, the refinement in targeting of axonal arbors during development is a phenomenon distinct from that seen during regeneration.
Lactoseries carbohydrates specify subsets of dorsal root ganglion neurons projecting to the superficial dorsal horn of rat spinal cord
Authors: Dodd J , Jessell TM
Published: March 2018

Cell surface carbohydrates are thought to play important roles in the development and differentiation of mammalian cells. In previous studies we have found that one population of dorsal root ganglion (DRG) neurons is specified by the expression of complex globoseries oligosaccharides (Dodd, J., D. Solter, and T. M. Jessell (1984) Nature 311: 469–472; Jessell, T. M., and J. Dodd (1985) Philos. Trans. R. Soc. Lond. (Biol.) 308: 271–281). We now report that monoclonal antibodies (MAbs) directed against backbone structures of lactoseries oligosaccharides define antigens present in the cytoplasm of a second, anatomically and functionally distinct subset of DRG neurons. Lactoseries carbohydrate structures identified by MAb A5 are restricted to small- and intermediate-diameter DRG neurons with central projections in the superficial dorsal horn of the rat spinal cord. The distribution of labeled terminals suggests that many of the DRG neurons that express lactoseries carbohydrates are likely to convey nociceptive information. More complex galactose- and fucose-substituted lactoseries structures recognized by MAbs LD2, KH10, TC6, TD10, LA4, and anti-Lewis a are segregated on subsets of DRG neurons that differ in their expression of substance P, somatostatin, and fluoride-resistant acid phosphatase and in their laminar termination in the superficial dorsal horn. The majority of lactoseries carbohydrate antigens identified in the cytoplasm of DRG neurons are also expressed on the surface of subsets of DRG neurons in culture. These studies establish that structurally defined carbohydrate differentiation antigens specify the majority of primary sensory neurons with cutaneous receptive fields. Moreover, lactoseries carbohydrate structures similar or identical to those expressed on neonatal DRG neurons in culture have been implicated in cell-cell interactions at early stages of preimplantation embryonic development. Our observations suggest strategies for testing the hypothesis that carbohydrates present on the surface of subsets of DRG neurons play a role in cell interactions that contribute to the laminar organization of sensory afferents in the developing spinal cord.
Density of somatic innervation on mammalian autonomic ganglion cells is inversely related to dendritic complexity and preganglionic convergence
Authors: Forehand CJ
Published: March 2018

I have studied superior cervical ganglion cells in mouse, hamster, rat, guinea pig, and rabbit by electron microscopy to determine how the distribution of synapses on these neurons is affected by the systematic differences in dendritic morphology and preganglionic convergence that are evident in the superior cervical ganglia of these species (Purves, D., and J. W. Lichtman (1985) Science 228: 298–302). The density of dendritic innervation is approximately the same in these animals regardless of target cell geometry (and always greater than the density of synapses on the cell soma); however, more complex ganglion cells, which are innervated by commensurately more axons, receive progressively fewer cell body synapses than geometrically simpler ganglion cells. Evidently the somatic membrane becomes a less favorable site for synapse formation as dendritic complexity and the number of inputs increase. This paradoxical decrease in the density of somatic innervation as preganglionic convergence increases may reflect competitive interactions between the axons innervating individual ganglion cells.
Identification of protein phosphatase 1 in synaptic junctions: dephosphorylation of endogenous calmodulin-dependent kinase II and synapse-enriched phosphoproteins
Authors: Shields SM , Ingebritsen TS , Kelly PT
Published: March 2018

A calcium/calmodulin-dependent protein kinase termed CaM-kinase II is a major component of synaptic junctions from forebrain and constitutes approximately 12% of total synaptic junction protein. CaM-kinase II phosphorylates at least seven polypeptides that are enriched in synaptic junctions, of which two represent the 50- and 60-kilodalton subunits of the protein kinase. In this report the nature of endogenous protein phosphatases which dephosphorylate each of the seven synaptic junction phosphoproteins was examined. Assays of synaptic junctions and other subcellular fractions from rat forebrain for type-1 and type-2 protein phosphatases revealed that protein phosphatase 1 (PrP-1) was specifically enriched in synaptic junctions with respect to cytosolic fractions. The activity of type-2 protein phosphatases was very low in synaptic junctions. Homogeneous PrP-1 from rabbit skeletal muscle was found to dephosphorylate each of the seven phosphoproteins in synaptic junctions. Inhibitors-1 and -2 were found to inhibit endogenous protein phosphatase activity by 70 to 80%. Since inhibitors-1 and -2 are specific inhibitors of PrP-1, these results indicate that this enzyme accounts for the majority of endogenous protein phosphatase activity in synaptic junctions. Approximately 15% of the protein phosphatase activity in synaptic junctions was type 2A, whereas PrP-2B and PrP-2C accounted for little, if any, of the activity toward endogenous or exogenous phosphoproteins. These results indicate that PrP-1 may be important in controlling the state of phosphorylation of synaptic junction proteins.
Characterization of proopiomelanocortin mRNA detected by in situ hybridization
Authors: Kelsey JE , Watson SJ , Burke S , Akil H , Roberts JL
Published: March 2018

In situ hybridization is a method for detecting specific nucleotide sequences by using a labeled complementary nucleic acid probe. We have characterized in situ hybridization in rat pituitary using a cDNA probe directed against a portion of proopiomelanocortin (POMC) mRNA to show its specificity in tissue sections. This characterization includes the size of the target mRNA from tissue processed for in situ hybridization, the dissociation pattern of the cDNA:mRNA hybrid, and quantitation of changes in POMC mRNA levels in the rat pituitary intermediate lobe detected both by in situ hybridization and “dot blot” techniques.
Selective staining of large projection neurons by monoclonal antibody to a glycoprotein of PC12 cells
Authors: Sajovic P , Moraru E , Greene LA , Shelanski ML
Published: March 2018

A monoclonal antibody has been produced against glycoproteins prepared from PC12 cells. This antibody stains PC12 cells in a rimlike fashion, whether they are fixed or living. When neuronally differentiated PC12 cells are used, neurites as well as somata stain. In the presence of complement, the antibody is cytotoxic to PC12 cells. These lines of evidence suggest that at least some of the binding is to an exposed component of the plasma membrane in these cells. Biochemical experiments directed at identifying the antigen(s) indicate specific recognition of glycoproteins of apparent molecular weights of approximately 160 and 95 kDa by SDS-PAGE. The antibody appears to be directed against a determinant on the protein moiety. The larger species is likely to be the same as a glycoprotein previously described (Lee et al., 1981), which has been found in PC12 cells, but not in brain. The monoclonal antibody we have produced, however, selectively stains a subset of neurons in brain. Specifically, it binds to Purkinje cells in cerebellar cortex, pyramidal cells in cerebral cortex and hippocampus, ganglion cells in retina, and some neurons, generally large, in most brain structures examined. No glia or nonneural tissues stain. We suggest that the neurons recognized by this antibody may be the projection cells of each structure. However, in contrast to PC12 cells, the antigen(s) bound in this case appears to be predominantly internal. This interpretation is supported by the appearance of stained cells in tissue; by the failure of the antibody to stain live dissociated neurons from brain; and by its failure to lyse sympathetic neurons in the presence of complement. Western immunoblots show that there is glycoprotein present in brain that is recognized by the antibody, and that it is enriched in a crude microsomal fraction prepared from that tissue. This material migrates on SDS gels as two bands of 130 and 95 kDa.
Analysis of local and wide-field movements in the superior temporal visual areas of the macaque monkey
Authors: Tanaka K , Hikosaka K , Saito H , Yukie M , Fukada Y , Iwai E
Published: March 2018

The middle temporal (MT) and medial superior temporal (MST) areas of the macaque cortex have many cells that respond to straight movements in the frontoparallel plane with directional selectivity (D cells). We examined their responses to movements of a bar, of a wide dot pattern, and to combined movements of the two in anesthetized and immobilized animals. D cells in MT showed a wide variety in the strength of the inhibitory field surrounding the excitatory center field. Responses of SI+-type cells to a bar moving across the excitatory field were suppressed when a wide dot pattern moved over the surround field in the same direction and at the same speed as the bar. Inhibition was selective to the direction and speed of the surround movement, and the effective area for inhibition occupied a wide area, which expanded in all radial directions. Responses of SI- -type cells to a center bar movement were changed little by a conjoint movement over the surround field. Consequently, SI- -type cells responded to wide-field movement as well as to stimuli confined within the excitatory field. Although D cells in MST commonly had large excitatory fields, a proportion of them (Figure type) responded to bar movement much more strongly than to wide- field movement. Their responses to a bar movement were suppressed direction-selectively by a conjoint movement of a wide dot-pattern background. The effective area for inhibition coexisted with the excitatory field in these cells. MST cells of the Nonselective type responded comparably well to the two stimuli, and those of the Field type responded much more strongly to wide-field movement than to bar movement. It is thus suggested that MT cells of the SI+ type and MST cells of the Figure type can detect a difference between movements of an object and its wide background, whereas MST cells of the Field type can detect a conjoint movement of a wide field, neglecting the movements of a single object.