bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of potassium current kinetics in bag cell neurons of Aplysia by an activator of adenylate cyclase
Authors: Strong JA
Published: March 2018

The bag cell neurons of Aplysia are neurosecretory cells which control egg-laying behavior. In their resting state, the cells have a high resting potential and show no spontaneous activity. In response to brief stimulation of a neural input, the cells depolarize and fire repetitively for up to 60 min. This afterdischarge is thought to be controlled by elevations of intracellular adenosine 3′:5′-monophosphate (cAMP). A voltage clamp study of bag cells in primary culture was undertaken in order to characterize the effects of cAMP on the cells' electrical properties. The transient outward potassium current (A- current) was studied before and after the application of forskolin (an activator of adenylate cyclase) and RO20–1724 (a phosphodiesterase inhibitor). These drugs reduced the amplitude of the A-current, primarily by speeding the inactivation process. The time constants for inactivation were speeded at all potentials, but the largest effects were seen at the more positive potentials (-40 to -15 mV), where the time constants were reduced 5-fold. Neither the activation process nor the steady-state parameters of inactivation were altered by the drugs. It is suggested that these changes in the A-current could explain the ability of the bag cells to fire repetitively during the afterdischarge.
Regeneration of sensory-motor synapses in the spinal cord of the bullfrog
Authors: Sah DW , Frank E
Published: March 2018

Sensory fibers innervating muscles in the arm of the bullfrog form specific patterns of monosynaptic connections with motoneurons in the spinal cord. We show here that these normal patterns are re-established after interruption of the second dorsal root (DR2) in tadpoles and postmetamorphic frogs. DR2 was either cut or crushed, and 2 to 8 months later the extent and specificity of regeneration were assessed anatomically and physiologically. Horseradish peroxidase labeling of DR2 showed that sensory afferents had regenerated back into the spinal cord to form local arborizations, as in the normal adult. However, few long-tract fibers in the dorsal columns regenerated. Intracellular recording from different classes of motoneurons at the level of DR2 revealed that triceps muscle sensory afferents had regenerated to form functionally appropriate synapses. As in the normal adult, stimulation of the triceps nerves elicited larger monosynaptic EPSPs in triceps motoneurons than in non-triceps motoneurons. Thus, in the central nervous system of the bullfrog, specific monosynaptic connections are re-formed within the region of local regeneration.
Neuronal responses of the rabbit cerebellum during acquisition and performance of a classically conditioned nictitating membrane-eyelid response
Authors: McCormick DA , Thompson RF
Published: March 2018

Neuronal activity was recorded from regions of the cerebellar cortex and dentate-interpositus nuclei during learning and/or performance of a classically conditioned nictitating membrane (NM-a third eyelid)/eyeblink response in the rabbit. It was found that neurons located within restricted portions of the ansiform lobule and anterior lobe cortical regions and of the dentate-interpositus nuclei respond in relation to the performance of the learned eyeblink response. Furthermore, chronic recordings from the dentate-interpositus nuclei revealed that these responses develop in close relation to the learning of the conditioned eyeblink response. Stimulation of the dentate- interpositus nuclei through the recording electrodes in some cases yielded eyelid closure and NM extension in both trained and untrained animals. Lesion of the axons of the dentate-interpositus nuclei (superior cerebellar peduncle), a manipulation which is known to abolish the learned eyeblink response, abolished the stimulation effect. We have previously reported that lesions of the dentate- interpositus nuclei cause abolition of the learned eyeblink response. In the present study, we report that lesions of the regions of cerebellar cortex projecting to the dentate-interpositus nuclei do not permanently abolish the conditioned response, although the amplitude- time course of the learned response could be affected. These results, together with results of other studies, demonstrate that the medial dentate and/or lateral interpositus nuclei are active during learning and performance of the conditioned eyeblink response, are capable of producing this learned response, and are essential for the learning and retention of the conditioned eyeblink response. Therefore, the medial dentate and/or lateral interpositus nuclei are a part of the essential neuronal circuit involved in the learning and production of the classically conditioned eyeblink response in the rabbit.
Voltage clamp analysis of sodium channels in normal and scorpion toxin- resistant neuroblastoma cells
Authors: Gonoi T , Hille B , Catterall WA
Published: March 2018

Sodium currents mediated by voltage-sensitive sodium channels in normal and scorpion toxin-resistant neuroblastoma cells were measured using a giga-ohm seal recording method in the whole cell patch configuration. The voltage and time dependence of sodium currents were similar in normal and mutant cell lines. Half-maximal activation occurred for test depolarizations in the range of -7 to -11 mV. Half-maximal inactivation occurred for pre-pulses in the range of -62 to -69 mV. Scorpion toxin from Leiurus quinquestriatus (100 to 200 nM) increased the time constant for sodium channel inactivation 6- to 9-fold, increased the peak sodium current 2.0 +/- 0.5-fold, shifted the voltage dependence of sodium channel activation 7 to 11 mV to more negative potentials, and made the voltage dependence of inactivation less steep. These effects were observed for both normal and scorpion toxin-resistant neuroblastoma cells. However, the effect of Leiurus toxin on the rate of inactivation was half-maximal at 1.7 nM for the parental cell line N18, in contrast to 5.4 or 39 nM for the scorpion toxin-resistant clone LV30 and 24 or 51 nM for LV10. These results show that scorpion toxin resistance results from a specific change in channel properties that does not impair normal function but causes an increase in the apparent KD for Leiurus toxin action on sodium channels.
Localization in mammalian brain of G-substrate, a specific substrate for guanosine 3',5'-cyclic monophosphate-dependent protein kinase
Authors: Detre JA , Nairn AC , Aswad DW , Greengard P
Published: March 2018

The regional and cellular distribution of G-substrate, a 23,000-dalton protein substrate specific for guanosine 3′,5′-cyclic monophosphate- dependent protein kinase, has been examined in mammalian brain using immunoprecipitation, radioimmunoassay, and peptide-mapping techniques. In rabbit brain, G-substrate was found to be highly concentrated in the cerebellum. The concentration of G-substrate in cerebellar cytosol was 27.2 pmol/mg. The concentrations of G-substrate in cortex, hippocampus, and caudate were only 1 to 2% of that found in cerebellum. Studies of neurological mutant mice lacking either Purkinje cells (PCD and nervous) or granule cells (weaver) suggested that, within the cerebellum, G-substrate is localized almost exclusively in Purkinje cells. A phosphoprotein present in noncerebellar brain regions, which co-migrated with G-substrate on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was shown by peptide mapping to consist predominantly of phosphatase inhibitor-1. Phosphatase inhibitor-1, a potent inhibitor of protein phosphatase-1, is known to share several physicochemical properties with G-substrate. In contrast to the results obtained with G-substrate, the concentration of phosphatase inhibitor-1 was significantly lower in cerebellum than in other major brain regions. These and other data suggest that G-substrate may be a Purkinje cell-specific protein phosphatase inhibitor.
Is cerebellar granule cell migration regulated by an internal clock?
Authors: Trenkner E , Smith D , Segil N
Published: March 2018

We have studied the time course of migratory behavior of cerebellar granule cells in the microwell tissue culture system. [3H]Thymidine served as a marker for particular granule cell generations. When cultured 4 hr after [3H]thymidine injection for 6 days in microwell cultures, labeled granule cells were seen to migrate along fiber bundles expanding between reaggregates called “cables” for 3 to 4 days. After 5 and 6 days in vitro the percentage of labeled non-migrating cells found in clusters in reaggregates and on cables increased considerably. Whereas unlabeled cells continued to migrate. Comparable results were obtained when granule cells developed in vivo for various times after label and their developmental state was determined in vitro. Cells from cerebellar populations labeled 1 to 4 days before culture maintained their ability to migrate in vitro, even after granule cells had entered the internal granule cell layer. In contrast, the percentage of migrating cells labeled 5 and 6 days before culture was reduced significantly. The results suggest that the time span of granule cell migration is predetermined intrinsically rather than by external signals.
Effects of dopamine antagonists on receptive fields of brisk cells and directionally selective cells in the rabbit retina
Authors: Jensen RJ , Daw NW
Published: March 2018

The effects of dopamine antagonists on the extracellularly recorded activity of ON- and OFF-center brisk ganglion cells and ON-OFF directionally selective ganglion cells in the rabbit retina were investigated. Haloperidol, fluphenazine, and cis-flupenthixol, infused in the arterial system supplying the eye, produced similar effects. In general, these drugs reduced the antagonistic surround responses of brisk ganglion cells, reduced the sustained excitation of the center response of ON-center brisk-sustained cells, reduced the leading edge response of ON-OFF directionally selective cells to moving light stimuli along with any sustained excitation to stationary light stimuli, and affected the spontaneous activity of the cells. These drug effects appear to be due to a blockade of D-1 (adenylate cyclase- linked) receptors and not to D-2 receptors. Neither S-sulpiride nor metoclopramide, two specific D-2 antagonists, had much effect. The findings are the first to describe the functional effects of dopamine antagonists on single cells in the mammalian retina and on ganglion cell activity in the vertebrate retina.
Novel organization of microtubules in cultured central nervous system neurons: formation of hairpin loops at ends of maturing neurites
Authors: Tsui HT , Lankford KL , Ris H , Klein WL
Published: March 2018

Using the high voltage electron microscope, we have examined cultured embryonic neurons in order to understand better the organization of microtubules in developing neurites. We found that, in embryonic chick retina neurons, microtubules were abundant in the ends of neurites and showed an unusual pattern of organization. Most striking was the presence of microtubule loops; after entering the flattened region of a growth cone, microtubules frequently made tight 180 degrees turns. Occasionally these looping microtubules re-entered the neurite and returned in the direction of the cell body. Positive identification of the loop structures as microtubules was made by specific immunocytochemical labeling. Quantitative analysis showed that more than half of the retina neurons that were dissociated on embryonic day 8 and kept in culture for 4 to 6 days (E8C4 and E8C6) contained at least one microtubule that made a 180 degrees turn at flat regions along or at the tips of neurites. The area within the loops typically contained larger membranous organelles, whereas only small vesicles were seen outside the loops. Fine filaments were seen to interconnect the loops at various places, suggesting the possibility that they played a role in maintaining the shape of microtubule loops. Examination of other neurons showed that tight microtubule loops were prominent in chick spinal cord neurons, but they were rarely seen in neurons of the sympathetic ganglia or dorsal root ganglia or in NG108- 15 cloned cells. Developmentally, no loops were observed in E8C1 retina neurons, but retina neurons dissociated from older embryos (12 days) did show loops after 1 day in culture; these data suggest that microtubule loops may be abundant around embryonic day 12 to 13 in the chick retina. The possible significance of this unusual microtubule organization to the control of neurite growth and bidirectional transport is discussed.
Calcitonin gene-related peptide immunoreactivity in the spinal cord of man and of eight other species
Authors: Gibson SJ , Polak JM , Bloom SR , Sabate IM , Mulderry PM , Ghatei MA , McGregor GP , Morrison JF , Kelly JS , Evans RM
Published: March 2018

Calcitonin gene-related peptide (CGRP) immunoreactivity was found throughout the entire spinal cord of man, marmoset, horse, pig, cat, guinea pig, mouse, rat, and frog. CGRP-immunoreactive fibers were most concentrated in the dorsal horn. In the ventral horn of some species large immunoreactive cells, tentatively characterized as motoneurons, were present. Pretreatment of rats with colchicine enhanced staining of these large cells but did not reveal CGRP-immunoreactive cell bodies in the dorsal horn. In the dorsal root ganglia, CGRP immunoreactivity was observed in most of the small and some of the intermediate sized cells. Substance P immunoreactivity, where present, was co-localized with CGRP to a proportion of the small cells. In the cat the ratio of substance P- immunoreactive to CGRP-immunoreactive ganglion cells was 1:2.7 (p less than 0.001). The concentration of CGRP-immunoreactive material in tissue extracts was determined by radioimmunoassay. In the dorsal horn of the rat spinal cord the levels of peptide were found to range from 225.7 +/- 30.0 pmol/gm of wet weight in the cervical region to 340.6 +/- 74.6 pmol/gm in the sacral spinal cord. In the rat ventral spinal cord, levels of 15.7 +/- 2.7 to 35.1 +/- 10.6 pmol/gm were found. The concentration in dorsal root ganglia of the lumbar region was 225.4 +/- 46.9 pmol/gm. Gel permeation chromatography of this extractable CGRP- like immunoreactivity revealed three distinct immunoreactive peaks, one eluting at the position of synthetic CGRP and the others, of smaller size, eluting later. In cats and rats, rhizotomy induced a marked loss of CGRP-immunoreactive fibers from the dorsal horn of the spinal cord. In the cat, unilateral lumbosacral dorsal rhizotomy resulted in a significant (p less than 0.05) reduction of extractable CGRP from the ipsilateral lumbar dorsal horn (5.6 +/- 1.2 pmol/gm of wet weight) compared to the contralateral side (105.0 +/- 36.0 pmol/gm of wet weight). We conclude that the major origin of CGRP in the dorsal spinal cord is extrinsic, from afferent fibers which are probably derived from cells in the dorsal root ganglia. The selective distribution of CGRP throughout sensory, motor, and autonomic areas of the spinal cord suggests many putative roles for this novel peptide.
Characterization of the cholinergic stimulation of phosphoinositide hydrolysis in rat brain slices
Authors: Gonzales RA , Crews FT
Published: March 2018

The stimulation of the formation of inositol phosphates by various cholinergic agonists and antagonists was studied in rat brain cortical slices. Incubation of the slices with [3H]inositol led to the incorporation of radioactivity into inositol lipids. The accumulation of inositol phosphates was then followed in the presence of 8 mM lithium which blocks the hydrolysis of inositol phosphate. The release of inositol phosphate was linear up to 15 min when stimulated by 1 mM carbachol. Acetylcholine, muscarine, and methacholine also stimulated the release of inositol phosphates with about the same efficacy as carbachol. Oxotremorine, arecoline, pilocarpine, and bethanechol were not as effective as carbachol at stimulating the accumulation of inositol phosphates. Indicative of partial agonist activity, oxotremorine and pilocarpine inhibited the maximal response induced by carbachol. Muscarinic antagonists atropine, scopolamine, and pirenzepine blocked the stimulation by acetylcholine in contrast to nicotinic antagonists, which had no effect. The brain regional response to carbachol-stimulated inositol phosphate release varied widely with large responses observed in the striatum, cerebral cortex, and hippocampus. Smaller responses were seen in the brainstem, hypothalamus, and cerebellum. Although carbachol stimulated inositol phosphate release in cortical slices in the absence of added calcium, EGTA completely blocked the response. These results suggest that the previously characterized stimulation of the incorporation of 32Pi into phosphatidylinositol by cholinergic agonists in synaptosomes (Fisher, S. K., P. D. Klinger, and B. W. Agranoff (1983) J. Biol. Chem. 258: 7358–7363) is due to the initial hydrolysis of inositol lipids.(ABSTRACT TRUNCATED AT 250 WORDS)
Identification of excitatory and inhibitory motoneurons in the nematode Ascaris by electrophysiological techniques
Authors: Walrond JP , Kass IS , Stretton AO , Donmoyer JE
Published: March 2018

A physiological preparation in which it is possible to record responses in muscle to stimulation of single motoneurons of the nematode Ascaris lumbricoides is described. With this preparation we have determined the physiological sign (E or I; excitatory or inhibitory) of the neuromuscular synapses of 21 identified motoneurons--12 are excitatory and 9 inhibitory. Ascaris motoneurons had previously been classified by morphological criteria into seven classes (Stretton, A. O. W., R. M. Fishpool, E. Southgate, J. E. Donmoyer, J. P. Walrond, J. E. R. Moses, and I. S. Kass (1978) Proc. Natl. Acad. Sci. U. S. A. 75: 3493–3497). Physiological studies were performed on members of five of these classes. Three classes of neurons (DE1, DE2, and DE3) are excitatory to dorsal muscle cells. Two classes (DI and VI) are inhibitory neurons which innervate the dorsal and ventral muscle cells, respectively. The motoneurons in Caenorhabditis elegans (White, J. E., E. Southgate, J. N. Thomson, and S. Brenner (1976) Philos. Trans. R. Soc. Lond. (Biol.) 275: 327–348) can be divided into seven morphological classes which are very similar to those in Ascaris. Based upon the structure-function correlation in Ascaris, we have predicted which motoneurons are excitatory and which are inhibitory in C. elegans.
Postsynaptic block of frog neuromuscular transmission by conotoxin GI
Authors: McManus OB , Musick JR
Published: March 2018

Conotoxin GI, a peptide neurotoxin contained in the venom of the marine snail Conus geographus, was applied to the cutaneous pectoris muscle of the frog, and the effects on the postsynaptic response to acetylcholine were examined. Conotoxin GI reversibly blocked nerve-evoked muscle contractions at concentrations greater than or equal to 3 to 4 microM. Micromolar concentrations of conotoxin GI significantly reduced the amplitude of miniature endplate potentials and membrane depolarizations produced by ionophoretic application of acetylcholine, suggesting that the toxin reduced the postsynaptic sensitivity to acetylcholine. The reduction in the sensitivity of the muscle to acetylcholine was not due to changes in muscle fiber resting membrane potential or input resistance. Conotoxin GI reduced the amplitudes but did not affect the rates of decay of focal, extracellularly recorded endplate currents or miniature endplate currents, suggesting that the toxin did not affect the lifetime of ion channels opened by acetylcholine. Miniature endplate currents decay five to six times more slowly than normal when acetylcholinesterase is blocked with neostigmine methyl sulfate due to repeated binding of acetylcholine to receptors as it diffuses from the synaptic cleft. Conotoxin GI reduced the amplitude and increased the rate of decay of miniature endplate currents recorded in the presence of neostigmine methyl sulfate, suggesting that the toxin reduced the binding of acetylcholine to endplate receptors. These results are consistent with the hypothesis that conotoxin GI blocks neuromuscular transmission at the frog endplate by reducing the binding of acetylcholine to receptors.
Characterization of an extended glutamate receptor of the on bipolar neuron in the vertebrate retina
Authors: Slaughter MM , Miller RF
Published: March 2018

The synaptic receptors of ON bipolar neurons are selectively activated by 2-amino-4-phosphonobutyrate, a glutamate analogue. This agent uniquely distinguishes these receptors from other types of excitatory amino acid receptors found in the retina. Various glutamate and aspartate analogues were used to assess the structure-activity characteristics of this receptor. The results suggest that it represents one class of glutamate receptor which can be distinguished by its preferential activation by acidic amino acid analogues that match the extended conformation of glutamate.
Maturation of visual callosal connections in visually deprived kittens: a challenging critical period
Authors: Innocenti GM , Frost DO , Illes J
Published: March 2018

The number of callosally projecting neurons (callosal neurons) which can be labeled in cortical areas 17 and 18 by horseradish peroxidase (HRP), injected in the contralateral visual cortex, is reduced to about 50% of normal in cats reared with their eyelids bilaterally sutured. In the same animals the density of HRP anterogradely transported to areas 17 and 18 is also decreased. The apparent loss of callosal neurons is limited to layers III and IV (subzone a), whereas layer VI (subzone c) is unaffected. The effect is obtained after 3 months or more but not after 1 month of deprivation. Two months of visual experience following deprivation do not restitute a normal number of callosal neurons. However, 10 days of normal visual experience preceding the deprivation are sufficient to prevent the effects of the latter. Animals deprived of vision after a short period of normal visual experience and animals allowed normal vision after 1 month of visual deprivation have a more widespread distribution of callosal neurons than do normal animals; in this way they are similar to previously described cats reared with convergent or divergent strabismus, monocular enucleation, or monocular eyelid suture. The results suggest that: vision is actively responsible for both the maintenance and the elimination of fractions of the juvenile callosal connections; the elimination which normally takes place during the second postnatal month requires normal binocular vision; and activity-dependent competition between callosal and other axons can explain the role of vision.
The effect of fibroblast growth factor on PC12 cells
Authors: Togari A , Dickens G , Kuzuya H , Guroff G
Published: March 2018

PC12 cells, which differentiate morphologically and biochemically into sympathetic neuron-like cells when treated with nerve growth factor, also respond to fibroblast growth factor. Some of the changes induced by fibroblast growth factor are similar to those seen after nerve growth factor treatment. Specifically, pituitary fibroblast growth factor causes the formation of processes initially comparable to those produced by nerve growth factor. However, in contrast to the outgrowth induced by nerve growth factor, which continues for several days, the outgrowth of processes induced by fibroblast growth factor ceases after about 3 days, even though fresh fibroblast growth factor is added. After about 6 days the processes induced by fibroblast growth factor have virtually disappeared. In this regard the processes induced by fibroblast growth factor are very similar to those induced by dibutyryl cyclic adenosine 3′:5′-monophosphate (dBcAMP). The addition of nerve growth factor and fibroblast growth factor together appears to produce a synergistic effect on process formation, as does the simultaneous addition of nerve growth factor and dBcAMP. Cells pretreated (or primed) with nerve growth factor are able to regenerate processes much more rapidly in the presence of nerve growth factor than cells which have not been pretreated. When fibroblast growth factor is added to cells primed with nerve growth factor, more rapid regeneration of processes also occurs. The regeneration of neurites in response to either factor is blocked by the addition of an inhibitor of methylation. The process formation induced by fibroblast growth factor is preceded, as is the outgrowth in response to nerve growth factor treatment, by an induction of ornithine decarboxylase, a decrease in the phosphorylation of a specific cytoplasmic protein, and an increase in the phosphorylation of a specific non-histone nuclear protein. The effects of fibroblast growth factor and of nerve growth factor on ornithine decarboxylase are additive. Fibroblast growth factor does not cause an increase in the activity of acetylcholinesterase; nerve growth factor does. Fibroblast growth factor does not appear to be acting through the nerve growth factor receptor. The binding of iodinated nerve growth factor to PC12 cells is specific and is not inhibited by the presence of fibroblast growth factor. In addition, anti-nerve growth factor serum does not interfere with the action of fibroblast growth factor.(ABSTRACT TRUNCATED AT 400 WORDS)
Directional asymmetries of optokinetic nystagmus: developmental changes and relation to the accessory optic system and to the vestibular system
Authors: Wallman J , Velez J
Published: March 2018

To investigate the relation of the directional organization of the accessory optic system (AOS) to that of its principal behavioral output, optokinetic nystagmus (OKN), we measured the eye velocity during OKN in response to 14 directions of stimulus motion, including horizontal, vertical, cyclorotational (rotations about the optic axis), and intermediate directions in both neonatal and older chickens. We found substantial and consistent OKN asymmetries between opposite directions of stimulus motion when the stimuli were viewed monocularly; the asymmetries were largest to combinations of cyclorotational and vertical stimulus motion and to horizontal stimulus motion. The highest gain of OKN in the older animals was in response to two directions of stimulus motion: horizontal temporal-to-nasal and a combination of excyclorotation and downward. In addition, OKN to upward moving stimuli was consistently better than to downward stimuli. The association of high OKN gain in the older animals with the pattern of visual motion produced by head movements exciting the contralateral anterior semicircular canal suggests a possible vestibular organization of the optokinetic system. The response pattern of the newly hatched chickens differed in three ways from that of the older animals: in the non- horizontal stimulus directions the best direction was to upward and excyclorotational stimulus motion; the horizontal asymmetry was somewhat less strong; and the OKN gain to high velocity horizontal stimulus motion was lower. The change in directional pattern of OKN over the first weeks of life appears related to a corresponding change in anatomy of the AOS.
Nerve growth factor-treated, neurite-bearing PC12 cells continue to synthesize DNA
Authors: Ignatius MJ , Chandler CR , Shooter EM
Published: March 2018

Cultures of rat pheochromocytoma (PC12) cells treated with beta-nerve growth factor (NGF) for up to 15 days continue to synthesize DNA. The present study compares the extent of maintained DNA synthesis in cells with and without processes and asks whether the observed DNA synthesis in differentiated PC12 cells reflects either the continued division of the cells or the formation of polyploid cells, or both. PC12 cells were grown on tissue coverslips for various lengths of time with or without 50 ng/ml of beta-NGF and then assayed for DNA synthesis by [3H]thymidine labeling and autoradiography. In 8-day-old control cultures (no NGF), 30% of the cells had labeled nuclei after a 2-hr [3H]thymidine pulse. In contrast, in cultures treated for 8 days with NGF, only 7% of the cells were labeled (i.e., still synthesizing DNA). The fractions of process-bearing and non-process-bearing cells with labeled nuclei were identical. Even after 14 days in NGF, 7% of the cells with neurites were still synthesizing DNA during any 2-hr period. With continuous [3H]thymidine labeling in the presence of NGF from 8 to 13 days, nearly 70% of the cells with neurites were labeled. The presence of neurites induced by NGF does not preclude continued (albeit reduced) DNA synthesis in these PC12 cells. To determine the fate of this newly synthesized DNA, nuclei extracted from NGF-treated PC12 cells were analyzed for the cellular distribution of DNA by combined propidium iodine staining and flow microfluorimetry. NGF treatment resulted in a 3-fold increase in the number of G2+M/4N cells along with the appearance of 8N cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Developmental neural kinship groups in the leech
Authors: Kramer AP , Weisblat DA
Published: March 2018

We have traced the developmental origins of various CNS neurons and glial cells of a leech to 10 clonally related groups of cells, the bilaterally paired M, N, O, P, and Q kinship groups. Each kinship group is descended from one of 10 identifiable blastomeres of the early embryo, the teloblasts. Of the approximately 200 neurons in each side of a segmental ganglion, 130 to 160 are in the ipsilateral N, 20 to 50 in the O, 8 to 12 in the P, 6 to 9 in the Q, and 3 to 6 in the M kinship group. A given identified neuron or glial cell was invariably found to belong to a particular kinship group, indicating that in leech development neuronal lineage is highly stereotyped. But cells of related function and morphology do not necessarily belong to the same neuronal kinship group: of the mechanosensory neurons, the T and N neurons belong to the N, the Pv neuron belongs to the P and the PD neuron belongs to the O kinship group. Similarly, glial cells arise from all four ectodermal teloblasts. Conversely, neurons within a kinship group are not obviously related in structure or function: the N kinship group includes sensory, motor, and effector neurons and interneurons: the O and P kinship groups each include sensory neurons and interneurons; both the P and Q groups contain representatives of three distinct morphological classes of interneurons. Consequently, in early development, the determinants of neuronal identity in the leech CNS are not segregated in any obvious thematic way in the cleavages that give rise to the five bilateral pairs of teloblasts. Rather, the neural kinship groups may be merely the evolutionary vestige of a primordial distributed nervous system, each quadrant of which was derived from one teloblast.
Knife cuts of entorhinal cortex: effects on development of amygdaloid kindling and seizure-induced decrease of muscarinic cholinergic receptors
Authors: Savage DD , Rigsbee LC , McNamara JO
Published: March 2018

This report examines the effect of transection of the entorhinal hippocampal projection on amygdaloid kindling. We found that: bilateral knife cuts of entorhinal cortex but not of dorsal neocortex antagonize the development of amygdaloid kindling; and bilateral knife cuts of entorhinal cortex eliminate the seizure-induced decrease in number of muscarinic receptors of dentate granule cells. We suggest the following interpretations of these data: the hippocampal formation circuitry facilitates the development of amygdaloid kindling; and the decline of muscarinic receptors after kindled seizures is due to excessive activation of granule cells by axons from entorhinal cortex, a noncholinergic afferent.
A panel of monoclonal antibodies to the rat olfactory epithelium
Authors: Hempstead JL , Morgan JI
Published: March 2018

BALB/c mice were immunized with dissected olfactory mucosa from young adult Sprague-Dawley-derived, CD, rats and antibody-secreting hybridomas were produced. Supernatants from hybridoma cultures were screened by immunocytochemical methods for their ability to react with specific cell populations in frozen sections of rat olfactory epithelium. Approximately 60 clones were identified that showed various degrees of specific staining. These have been classified on the basis of their particular staining specificities. One group of monoclonal antibodies, designated LUM, reacts with the luminal surface of the epithelium. Closer examination reveals these antibodies to react variously with the apical brush border of sustentacular cells, respiratory cilia, and the luminal membrane of respiratory cells. Another group of monoclonal antibodies reacts primarily with sustentacular cells, as is indicated by the SUS prefix. Some antibodies in this group also react with the membranes of respiratory cells and the cells comprising the acini of Bowman's glands. A larger group of antibodies reacts with olfactory neurons and/or their axons, as denoted by the NEU prefix. This group can be further subdivided by the criteria of whether both the olfactory nerve and vomeronasal nerve react with the same monoclonal antibody. A fourth group of monoclonal antibodies, designated GLA, reacts with Bowman's glands and in some instances with secretory cells present in the respiratory mucosa. Two clones, BCL, stain at the level of the basal cell layer just above the lamina propria. A number of other antibodies react with cells and structures of the epithelium that have not been previously described. One of this group, NIS-1, stains globular structures present in the mucosa of the neuroepithelium.
Phase and amplitude computations in the midbrain of an electric fish: intracellular studies of neurons participating in the jamming avoidance response of Eigenmannia
Authors: Heiligenberg W , Rose G
Published: March 2018

Electric fish monitor modulations in sensory feedback from their own electric organ discharges (EODs) to locate moving objects and to detect interfering EODs of their neighbors. The gymnotoid genus Eigenmannia minimizes detrimental effects of jamming by EODs of its neighbors by shifting its own EOD frequency away from a neighbor's EOD frequency that is too close to its own. Since the animal lowers its own frequency if its neighbor's frequency is higher and raises its frequency if its neighbor's frequency is lower, this jamming avoidance response (JAR) requires that the animal determine the sign of the difference frequency, Df, between the interfering EODs. Eigenmannia obtains this information by evaluating modulations in the amplitude and phase which its nearly sinusoidal EOD signal experiences due to the interference with the neighbor's EODs. The necessary logical operations are executed in the dorsal torus semicircularis, an analogue of the inferior colliculus of higher vertebrates, and are similar to operations underlying directional hearing. By intracellular labeling of physiologically identified cells we have identified the anatomy and functional characteristics of neurons involved in the processing of amplitude and phase information. The JAR is controlled by hierarchical and parallel processing of information in several laminae of somatotopically ordered neurons. Phase differences between signals received by electroreceptors in different parts of the body surface are computed in lamina 6. Information about differential phase is then relayed to multipolar cells in the deeper laminae 8, b and c, which also receive information about modulations in local signal amplitude. These cells are excited by a rise or fall of amplitude as well as by a lead or lag of phase. According to their responses to either of these two variables, these neurons can be divided into four classes. These classes encode all information necessary for the control of the JAR and project to the optic tectum. Dynamic properties and sensory specificities of the JAR are not found in individual, properly tuned neurons but rather emerge statistically from the joint effects of a large population of imprecisely tuned neurons. This system is characterized by a distributed pattern of organization and by the absence of a small number of key neurons whose malfunction would jeopardize the behavioral response. The complexity of this neural machinery appears unnecessary for the logically simple task of the JAR, and it suggests that this behavior was acquired later in evolution by being derived from more general motor responses to moving objects.(ABSTRACT TRUNCATED AT 400 WORDS)
Activity-dependent shrinkage of extracellular space in rat optic nerve: a developmental study
Authors: Ransom BR , Yamate CL , Connors BW
Published: March 2018

Activity-dependent shrinkage of extracellular space (ECS) is described in a simple model of the mammalian central nervous system, the rat optic nerve. In response to neural activation, the ECS of the mature nerve rapidly and reversibly decreases by as much as 20%. Activity- dependent ECS shrinkage is not present in neonatal nerves but develops over the first 2 weeks of life, roughly coincident with the appearance of glial cells in this structure. These and other observations suggest that activity-dependent ECS shrinkage results from fluid and electrolyte movements into glial cells.
Input and output changes of an identified neural pathway are correlated with associative learning in Hermissenda
Authors: Goh Y , Lederhendler I , Alkon DL
Published: March 2018

The effect of associative training on an identified putative motoneuron (MN1) in an identified visual input-output neural pathway was studied in Hermissenda crassicornis. The increased impulse frequency of the MN1 cell in response to a light step (MN1-LR) was found to be smaller up to 54 hr after associative training with paired light and rotation stimuli. No change was found in animals which received these training stimuli randomly. The MN1 activity in darkness, namely, baseline impulse frequency, spike amplitude, input resistance, and resting potential, did not change after training. The MN1-LR was positively correlated on retention days with the behavioral latency of the animal to enter the illuminated area of a light intensity gradient. However, the input resistance of the type B photoreceptor was inversely correlated with this behavioral latency as well as with MN1-LR. These findings suggest that the reduction of MN1-LR may be caused by the biophysical changes which have been found in the type B photoreceptor membrane. Furthermore, these findings support several other studies which indicate that specific biophysical changes in the type B photoreceptor membrane play a causal role in the observed behavioral modifications after associative training in Hermissenda.
Thyrotropin-releasing hormone (TRH) receptors. Localization by light microscopic autoradiography in rat brain using [3H][3-Me-His2]TRH as the radioligand
Authors: Mantyh PW , Hunt SP
Published: March 2018

Thyrotropin releasing hormone (TRH) is a putative neurotransmitter in both the central and peripheral nervous system. In the present report, we have used autoradiography coupled with densitometric analysis of tritium-sensitive film to investigate the distribution of [3H][3-Me- His2]TRH [( 3H]MeTRH)-binding sizes in the rat brain. Previous pharmacological reports have established that many of these [3H]MeTRH- binding sites have a structure-activity profile consistent with being a physiological TRH receptor. A high level of TRH receptors were observed in the accessory olfactory bulb, lateral nucleus of the amygdala, dentate gyrus, and entorhinal cortex. Moderate levels of TRH receptors were observed in the rhinal cortex, hypothalamus, superior colliculus, several brainstem motor nuclei, and lamina I of the spinal trigeminal nucleus pars candalis, while low concentrations of receptors are present in the cerebral cortex, striatum and ventral horn of the spinal cord. Very low levels of receptors were observed in the globus pallidus and in most nuclei of the dorsal thalamus. Comparisons of the distribution of TRH receptors to TRH-immunoreactive content indicates that, while in some areas of the brain there is a rough correlation between levels of TRH peptide and its receptor, in most brain areas there is little obvious correlation between the two. While such a discrepancy has been observed for other peptides and their receptors, the extensive distribution of TRH receptors in the central nervous system does provide an explanation for the variety of behavioral effects observed when TRH is infused into the central nervous system.
Proprioceptive influences on auditory and visual spatial localization
Authors: Lackner JR , Shenker B
Published: March 2018

We evaluated the influence of proprioceptive information about arm position on the perceptual localization of auditory and visual targets attached to the hand. Our approach was to distort the perceived position of the restrained arm by means of mechanical vibration of the biceps brachii muscle; such vibration elicits compelling apparent extension of the stationary forearm (Goodwin, G. M., D. I. McCloskey, and P. B. C. Matthews (1972) Science 175: 1382–1384, Brain 95: 705– 748), and subjects report changes in the apparent directions of the auditory and visual targets attached to their hand. These changes are in the same direction and plane as apparent arm motion and their onsets are coincident with or lag slightly behind the experienced displacement of the arm. While visual motion is being experienced, a subject's eyes remain steadily fixating the target light. The pattern of findings demonstrates that proprioceptive information about limb position can influence the central representation of gaze and auditory localization can be similarly influenced. The biasing of auditory localization indicates that identical patterns of arrival time and intensity cues at the two ears can give rise to the perception of sounds in widely disparate spatial positions in relation to the head and body, depending on the proprioceptive representation of the direction of the sound source.
Differential ontogeny of multiple opioid receptors (mu, delta, and kappa)
Authors: Spain JW , Roth BL , Coscia CJ
Published: March 2018

We investigated the postnatal ontogeny of opioid receptors in rat brain under assay conditions which, when combined with computerized analysis, effectively reflect the developmental profile of high affinity binding to mu, delta, and kappa subpopulations. Concentrations of mu sites were assessed with the selective ligand 3H-[D-ala2,mePhe4,gly-ol5]enkephalin (DAGO). The other two sites were analyzed in binding assays with less selective radioligands but in the presence of specific unlabeled ligands which suppress cross-reactivity. We utilized 3H-[D-ala2,D- leu5]enkephalin (DADL) in the presence of 10 nM DAGO to label delta sites and 3H-ethylketocyclazocine (EKC) in the presence of 100 nM DADL + 100 nM [D-ala2,mePhe4,Met(0)ol5]enkephalin to detect kappa receptors. After birth, the density (femtomoles per milligram of wet weight) of mu sites declined for several days and then rose sharply over the next 2 weeks, increasing 2-fold by adulthood. Delta (delta) sites appeared in the second week postnatal and increased more than 8-fold in the next 2 weeks. Levels of kappa receptors were relatively low at birth and increased slowly (2-fold, overall). Computerized analyses of binding data revealed that DAGO and DADL were binding to single populations of sites throughout the postnatal period. DAGO and EKC affinities did not fluctuate in this period, whereas DADL affinities were low for the first week and then rose to adult levels. In summary, mu, kappa, and delta receptors exhibit differential postnatal developmental profiles. The former two are present at birth, whereas the latter appears in the second week. The postnatal increase for all three sites appear to be preceded by the previously demonstrated emergence of opioid peptides.
Morphology and serotonergic innervation of physiologically identified cells of the guinea pig's myenteric plexus
Authors: Erde SM , Sherman D , Gershon MD
Published: March 2018

Ganglion cells of the myenteric plexus of the guinea pig were physiologically classified as to cell type using intracellular microelectrodes containing horseradish peroxidase (HRP). Interganglionic fiber tracts were then stimulated in an attempt to elicit slow excitatory postsynaptic potentials (EPSPs) in the impaled cells. The presence or absence of a slow EPSP was noted, following which the cells were injected with HRP through the recording micropipette and finally were incubated with tritiated 5- hydroxytryptamine ([3H]-5-HT; 0.5 microM) and desmethylimipramine (10 nM). The preparations were examined by light and electron microscopy (EM) for which the physiologically identified, HRP-injected neurons were demonstrated histochemically and serotonergic nerve terminals were simultaneously demonstrated radioautographically. Forty-seven cells were physiologically identified, injected with HRP, and studied by light microscopy. Of these, 22 were also fully analyzed by electron microscopy. The sample included 13 type I/S cells (6 analyzed by electron microscopic radioautography), 16 type II/AH cells (10 analyzed by electron microscopic radioautography), and 18 nonspiking (NS) cells (6 analyzed by electron microscopic radioautography). Slow EPSPs were only observed in type II/AH cells. All five of the fully analyzed subset of type II/AH cells that manifested a slow EPSP were contacted by serotonergic terminals. These terminals were found on 7 of 10 type II/AH cells, 2 of 6 type I/S cells, and 0 of 6 NS cells. Serotonergic terminals, therefore, contacted type II/AH cells (p less than 0.05) and especially those that showed a slow EPSP (p less than 0.005) more frequently than other types of ganglion cells. Morphologically, cells with short, stubby dendrites were reproducibly found to be type I/S cells, and glia could be recognized by their astrocytic appearance; however, cell shape did not otherwise correlate with physiological cell type. These data are compatible with and provide support for the hypothesis that 5-HT is one of the mediators of slow EPSPs in the myenteric plexus.
Development of the rat superior cervical ganglion: ingrowth of preganglionic axons
Authors: Rubin E
Published: March 2018

The growth of sympathetic preganglionic axons has been studied in the fetal rat. Preganglionic axons first emerge from the spinal cord and enter the paravertebral chain of ganglia between days 12 and 13 of gestation (E12 to E13). By E14, hundreds of preganglionic neurons have sent axons into the sympathetic chain. Even at this age, the arrangement of the preganglionic axons conforms to the adult organization in a number of ways. As in maturity, these axons leave the spinal cord only through the ventral root of the segment in which their cell bodies reside. Furthermore, axons grow into the superior cervical ganglion only from the same set of spinal segments as supply this ganglion in maturity, and in correct segmental proportions, although there is a slight rostral-to-caudal lag along the spinal cord in the full establishment of the projection. The development of appropriate projections in this system owes little to the growth of axons along stereotyped pathways. Rather, preganglionic organization apparently reflects a more general instruction that governs the relative number of axons from each spinal segment which course rostrally or caudally within the sympathetic chain. The appropriate distribution of preganglionic axons early in development suggests that a fiber's segmental level of origin biases the axon to grow in a particular direction.