bluuebunny/crossref_metadata_2025 huggingface dataset:
The activation of inositol phospholipid metabolism as a signal- transducing system for excitatory amino acids in primary cultures of cerebellar granule cells
Authors: Nicoletti F , Wroblewski JT , Novelli A , Alho H , Guidotti A , Costa E
Published: March 2018

L-Glutamic, L-aspartic acids and a number of their structural analogs, including quisqualic, kainic, ibotenic, quinolinic, and N-methyl-D- aspartic (NMDA) acids, increase inositol phospholipid hydrolysis when added to primary cultures of cerebellar granule cells, as is reflected by an enhanced formation of 3H-inositolmonophosphate (3H-IP1) in the presence of Li+. L-Glutamic acid also enhances the formation of the initial products of inositol phospholipid hydrolysis, 3H-inositol di- (3H-IP2) and triphosphate (3H-IP3). In the absence of extracellular Ca2+, L-glutamic acid fails to enhance 3H-IP1 formation, but still increases 3H-IP2 and 3H-IP3 formation. The stimulation of 3H-IP1 formation elicited by L-glutamic acid is reduced by DL-2-amino-5- phosphonovaleric acid (APV) and gamma-glutamylglycine and, to a lesser extent, by 2,3-cis-piperidindicarboxylic acid (PDA). The stimulation of 3H-IP1 formation by kainic acid is antagonized by PDA and gamma- glutamylglycine, but it is almost unaffected by APV. The increase in 3H- IP1 formation elicited by quisqualic acid is not reduced by any of the dicarboxylic amino acid receptor antagonists that we have tested. We conclude that different subtypes of excitatory amino acid recognition sites are associated with inositol phospholipid metabolism in primary cultures of cerebellar granule cells.
Adenosine-containing neurons in the brain localized by immunocytochemistry
Authors: Braas KM , Newby AC , Wilson VS , Snyder SH
Published: March 2018

Specific sensitive rabbit antisera directed against the adenosine derivative laevulinic acid (O2′,3′-adenosine acetal), which are capable of detecting as little as 1 pmol of adenosine by radioimmunoassay and which require more than 1000- to 40,000-fold greater concentrations of adenine nucleotides to displace adenosine binding to antisera, have been developed. These antisera were employed to localize adenosine immunoreactivity throughout the rat CNS using the peroxidase- antiperoxidase (PAP) complex and avidin-biotin-peroxidase complex (ABC) immunocytochemical techniques. Intense staining for adenosine immunoreactivity was localized to the cytoplasm of perikarya and fibers in neuronal cell groups of discrete rat brain regions. Areas containing highest levels of immunoreactivity included the pyramidal cells of the hippocampus, the granule cells of the dentate gyrus, subnuclei of the thalamus, amygdala, and hypothalamus, the primary olfactory cortex, and many motor and sensory nuclei of the brain stem and spinal cord. High levels also occurred in certain layers of the cerebral cortex, the caudate-putamen, the septal nuclei, and the Purkinje cell layer of the cerebellum. Varying the extent of tissue hypoxia altered only the levels of endogenous immunoreactive adenosine without changing the pattern of distribution of the immunoreactivity. Staining was abolished by immunoabsorption and by pretreatment of tissue sections with adenosine deaminase. The localization of adenosine to discrete neuronal groups in the brain supports the possibility of a neurotransmitter or neuromodulatory role for adenosine.
A partially purified preparation of isolated chemosensory cilia from the olfactory epithelium of the bullfrog, Rana catesbeiana
Authors: Anholt RR , Aebi U , Snyder SH
Published: March 2018

Cilia at the tips of dendritic processes of olfactory receptor cells are the sites of initial recognition and transduction events in olfactory reception. We have detached cilia from the olfactory epithelium of the bullfrog, Rana catesbeiana, via a calcium shock and partially purified them in high yield (226 +/- 19 micrograms protein/frog, n = 14) by sucrose gradient centrifugation. The cilia appear to undergo osmotic lysis during the isolation procedure, forming isolated axonemal structures and ciliary plasma membrane vesicles with diameters of 100–500 nm and an internal volume of 2.3 +/- 0.5 microliter/mg protein. PAGE in SDS reveals approximately 30 protein bands, among which cytoskeletal components, such as tubulin and actin, are readily identifiable by immunoblotting. Approximately 15 glycoprotein bands reactive with concanavalin A are discernible with major glycopeptides at apparent molecular weights of 56–65, 95, and 116 kDa. In contrast to olfactory cilia, respiratory cilia, isolated from the palate of the frog, do not contain the prominent glycopeptides observed for olfactory cilia. The 56–65 kDa glycopeptide region reacts with antiserum against chick kidney, Na+/K+-ATPase, and contains the beta subunit of this enzyme. In addition, we have identified the alpha and beta subunits of a guanine nucleotide-binding protein (G-protein) in the olfactory cilia preparation. This preparation of isolated olfactory cilia from Rana catesbeiana represents a readily accessible model system for studies of initial events in chemosensory recognition and signal transduction in the olfactory system.
Catecholamine, serotonin, and substance P-like peptide containing intrinsic neurons in the mudpuppy parasympathetic cardiac ganglion
Authors: Neel DS , Parsons RL
Published: March 2018

The mudpuppy cardiac ganglion contains 2 neuron types: large parasympathetic postganglionic projection neurons and smaller intrinsic neurons originally described by McMahan and Purves (1976) as intensely fluorescent (SIF) cells. The function of these SIF cells, present in the mudpuppy cardiac ganglion, is unknown. Further, direct application of catecholamines, which are thought to be contained in SIF cells, to the parasympathetic postganglionic cells has no effect (Hartzell et al., 1977). As SIF cells in other ganglion preparations recently have been shown to contain putative transmitter substances in addition to catecholamines, immunocytochemical experiments were conducted to test for the presence of additional transmitter substances in the SIF cells within the cardiac ganglion. Whole-mount septal preparations were dissected from Necturus maculosus and processed for indirect immunocytochemistry. The results indicated that many of these intrinsic neurons contained 5-HT or a substance P-like peptide, or both. Many small intrinsic neurons which contain either substance P or 5-HT were also positive for aqueous-aldehyde-induced fluorescence, indicating the presence of a catecholamine. Finally, some of these cells appeared to contain all 3: a catecholamine, 5-HT, and a substance P-like peptide.
Eye-movement-dependent loss in vision and its time course during vergence
Authors: Manning KA
Published: March 2018

The attenuation of vision that has long been known to accompany saccadic eye movement has a significant component that is not attributable to visual masking or image smear, and this suppression of vision is now associated with nonsaccadic movement. The purpose of the present experiment was to determine the time course of visual suppression during a vergence eye movement. Suppression was evaluated psychophysically in human observers by measuring their loss of sensitivity to a brief, full-field decrement of light during 6 degrees- 9 degrees convergence. Vergence-related suppression was similar in total duration and amplitude to saccadic and blink-related suppression. Since these other forms of oculomotor activity are vastly different in speed and total duration, it is unlikely that suppression results directly from the activity itself. Instead, these results support the hypothesis that a common, more centrally originating, suppression of vision occurs during eye movements, including saccades, eyeblinks, and vergence. Thus, while vision during eye movements can often be reduced through masking and smearing effects, the movement-dependent visual suppression measured in these experiments is a more generally occurring event.
Visual recognition in monkeys following rhinal cortical ablations combined with either amygdalectomy or hippocampectomy
Authors: Murray EA , Mishkin M
Published: March 2018

Performance on a visual recognition task was assessed in cynomolgus monkeys with ablations of rhinal (i.e., ento-, pro-, and perirhinal) cortex in combination with either amygdalectomy or hippocampectomy, as well as in unoperated controls. Removal of the hippocampal formation plus rhinal cortex resulted in a mild recognition deficit, whereas removal of the amygdaloid complex plus rhinal cortex resulted in a severe deficit. Comparison of the results with those of an earlier study (Mishkin, 1978) indicates that adding a rhinal cortical removal to hippocampectomy yields little, if any, additional impairment in recognition. By contrast, adding a rhinal cortical removal to an amygdalectomy has a profound effect; indeed, the recognition impairment in monkeys with amygdaloid plus rhinal removals was at least as severe as that seen in monkeys with combined amygdaloid and hippocampal removals. Taken together, these results support the conclusion that combined damage to the amygdaloid and hippocampal systems is necessary to produce a severe recognition deficit. In addition, they suggest that the effect of ablating the rhinal cortex is equivalent to that of removing the entire hippocampal formation, presumably because the rhinal cortical ablation disconnects the hippocampus from its neocortical input.
Egg-laying hormone genes of Aplysia: evolution of the ELH gene family
Authors: Nambu JR , Scheller RH
Published: March 2018

Evolution of the egg-laying hormone (ELH) gene family was examined in the genus Aplysia using genomic Southern blotting, gene cloning, and immunocytochemical techniques to identify and characterize homologous sequences. Most of the species examined have fewer than the 4–5 ELH- related genes present in the A. californica genome (Mahon et al., 1985; Scheller et al., 1983). In A. parvula there are 2 ELH genes, and unlike A. californica, no sequences were found to encode the A or B peptides. The 2 A. parvula ELH genes share at least 90% DNA sequence homology, while the homology between the A. parvula and A. californica ELH genes is 71%. The structural organization of the A. parvula ELH precursor is quite similar to the ELH precursor of A. californica, with all but one of the potential proteolytic cleavage sites conserved. The overall amino acid homology between the A. parvula and A. californica ELH precursors is 66%; however, the alpha and beta bag cell peptides, as well as ELH, are more highly conserved, suggesting that these peptides have important physiological and behavioral roles within both Aplysia species. Immunocytochemical studies indicate that the A. parvula ELH genes are expressed in 2 bag-cell-like clusters of about 40 neurons each in the abdominal ganglion. There does not appear to be an atrial gland in A. parvula; however, ELH-immunoreactive peripheral neurons and their processes are observed along the perimeter of the large hermaphroditic duct.
Ultrastructure of gonadotropin-releasing hormone neuronal structures derived from normal fetal preoptic area and transplanted into hypogonadal mutant (hpg) mice
Authors: Silverman AJ , Zimmerman EA , Kokoris GJ , Gibson MJ
Published: March 2018

The hpg mutant mouse lacks the neurohormone gonadotropin-releasing hormone (GnRH) and hence has a reproductive deficit. This deficit can be corrected by placement of normal fetal preoptic area into the third ventricle (see Krieger et al., 1985). We have now used ultrastructural immunocytochemistry to investigate the morphology of GnRH neurons in such intraventricular grafts, the routes that their axons take as they exit into the host, and the neurosecretory terminations that they make in the host median eminence. The GnRH cells in the transplant were similar in morphology to that reported for such cells in the preoptic area of other rodents. There was a large central nucleus, frequently indented and containing 1 or 2 nucleoli. The thin rim of cytoplasm was filled with rough endoplasmic reticulum, Golgi stacks, and mitochondria. Both dendritic and axonal profiles were identified, and a modest synaptic input to the former was found. Between the host and the implant a complex multilayered ependymal zone developed, and it was through this region that GnRH axons exited into the host arcuate nucleus and median eminence, usually surrounded by ependymal or glial elements. Within the median eminence, GnRH terminals were in close association with fenestrated blood vessels forming a normal neurosecretory terminus.
Pattern of intracranial and extracranial projections of trigeminal ganglion cells
Authors: O'Connor TP , van der Kooy D
Published: March 2018

The trigeminal sensory innervation of the major cerebral vessels is thought to carry the nociceptive information during a migraine headache, and this pain is usually referred to the forehead area. Using retrograde tracing techniques, we have described the distribution of sensory trigeminal cells that innervate the middle cerebral artery (MCA) and the forehead. Nearest-neighbor analysis of the ophthalmic division of the trigeminal ganglion revealed that cells innervating the forehead tend to be clumped around individual cells that innervate the MCA. An average of less than 1 cell per animal was found to project divergent collaterals to both areas. The close association of ganglion cell bodies innervating the cerebral vasculature and those innervating forehead areas may underlie the convergence of their central processes onto common brain-stem trigeminal nucleus cells, and thus the referral of headache pain. In contrast to the lack of ganglion cells with axonal collaterals to the cerebral vasculature and forehead, a significant population of cells that innervate the MCA also have collateral projections to other cerebral arterial branches (branches of the middle meningeal artery), as well as the surrounding dura. Thus, the innervation targets of individual trigeminal cells are very widespread intracranially (including arteries and dura), but separate cells in the ophthalmic division innervate extracranial targets.
Differential down-regulation of D1-stimulated adenylate cyclase activity in rat forebrain after in vivo amphetamine treatments
Authors: Roberts-Lewis JM , Roseboom PH , Iwaniec LM , Gnegy ME
Published: March 2018

Amphetamine has complex behavioral actions in the rat that depend upon the release of dopamine in striatal and mesolimbic brain regions. To explore a possible role of the dopamine-sensitive cAMP second-messenger system in mediating these effects, we examined the effects of in vivo amphetamine treatments on the D1 receptor-coupled adenylate cyclase system in membranes from striatal and mesolimbic rat brain regions. The results show that amphetamine produces a regional, dose- and time- dependent down-regulation of adenylate cyclase activity. Intermediate and high doses of amphetamine (2.5 and 7.5 mg/kg, respectively), but not a low dose (1.0 mg/kg), resulted in a decrease in the apparent Vmax and/or an increase in the apparent Ka for the selective D1 partial agonist, SKF38393, in striatal membranes 30 min after amphetamine treatment. Treatment of rats with 7.5 mg/kg amphetamine for 30 and 60 min, but not 10 min, similarly resulted in a down-regulation of D1- mediated adenylate cyclase activity in striatal membranes. In contrast, in mesolimbic tissues, no amphetamine treatment at any time resulted in an alteration of SKF38393-stimulated adenylate cyclase activity relative to saline controls. The results of behavioral analyses also showed that animals exhibiting intense stereotypies had significantly lower striatal apparent Vmax values than did those animals engaged in moderate or no behavioral activity at the time of decapitation. These findings demonstrate that amphetamine treatments result in a down- regulation of striatal, but not mesolimbic, dopamine-sensitive adenylate cyclase activity that parallels the intense, stereotyped behaviors characteristic of dopaminergic activation in the striatum.
Integrative mechanisms controlling directional sensitivity of an identified sensory interneuron
Authors: Jacobs GA , Miller JP , Murphey RK
Published: March 2018

Several identified interneurons in the cricket cercal afferent system display directional sensitivity to wind stimuli: the spike frequency of these cells depends on the wind direction with respect to the animal's body. Factors determining the directional sensitivity of one of these identified interneurons (interneuron 10-3) were studied in detail. This cell has 3 dendritic branches that arborize in 3 distinct regions of the terminal abdominal ganglion. Using 2 independent methods, it was demonstrated that the dendrites have different receptive fields to wind stimuli. First, small patches of filiform hairs, whose afferents projected to individual dendrites, were isolated and selectively stimulated. In each case the response of the cell matched the receptive field of the afferents in the patch. Second, a laser beam directed through the stereo dissecting microscope was used to photoinactivate small portions of the cell in situ during intracellular recording. By isolating or ablating individual dendrites, the contributions of each of the 3 dendrites to the overall receptive field were assessed. Although the receptive field of the whole cell could be predicted by a summation of the receptive fields of all 3 dendrites, the precise directional sensitivity of the cell could not be predicted by a simple linear summation of the receptive fields of each dendrite. Two factors were found to account for this nonlinearity of summation. The first factor was polysynaptic inhibition from other interneurons within the terminal abdominal ganglion. Wind directions that activate inhibition in interneuron 10-3 were identified, and the specific classes of filiform afferents that activate the inhibitory pathway were determined. The net effect of the inhibition was to "sharpen" the directional sensitivity of 1–3 by selectively decreasing the cell's response to specific excitatory inputs. The second factor that contributed to directional sensitivity was the complex electroanatomy of the interneuron. The probable location of the spike-initiating zone (SIZ) was determined by using the laser photoinactivation technique. The relative efficacies of synaptic inputs onto the 3 different branches were then interpreted with respect to their different electrotonic distances from the SIZ. On the basis of the data obtained in this report, we present a qualitative model for the basis of directional sensitivity in this cell.
Distribution of neuronal receptors for nerve growth factor in the rat
Authors: Richardson PM , Issa VM , Riopelle RJ
Published: March 2018

To survey the distribution of neuronal receptors for NGF, sections of the rat brain, spinal cord, and peripheral ganglia were incubated in vitro with radioiodinated NGF and examined by autoradiography. NGF binds selectively with high affinity to most sympathetic neurons and many primary sensory neurons together with their intraspinal or intramedullary axons. In autoradiographs of the brain, labeled neuronal perikarya are seen in the basal forebrain, the caudate-putamen, the medulla oblongata, the ventral cochlear nucleus, and the dorsal nucleus of the lateral lemniscus. The distribution of neurons binding NGF resembles the distribution of cholinergic neurons in the forebrain, but these 2 systems overlap very little in the brain stem. In extracts of the brain or spinal cord enriched for plasma membranes, avid binding sites are regionally manifest with properties similar to those of fetal peripheral neurons. The localization of neurons expressing the high- affinity receptor for NGF defies simple correlation with neurotransmitter function or embryogenesis.
The role of calcium in the rapid adaptation of an insect mechanoreceptor
Authors: French AS
Published: March 2018

The femoral tactile spine of the cockroach is a rapidly adapting mechanoreceptor in which the response to a step displacement is a burst of action potentials lasting about 1 sec. This adaptation seems to occur during the encoding of action potentials from receptor current, since there is no evidence of adaptation in the receptor potential, and the adaptation can be demonstrated by direct electrical stimulation of the single sensory neuron in the spine. We have recently presented evidence for a calcium-activated potassium conductance in the tactile spine receptor neuron, although it was not directly linked to adaptation. Since this conductance could be involved in the rapid adaptation of the tactile spine neuron, we sought an association between adaptation and the entry of calcium ions into the cell. Adaptation in the tactile spine neuron was examined by direct electrical stimulation using a randomly fluctuating current followed by frequency-response analysis. The dynamic behavior was studied as a function of the concentration of calcium ions in the bathing solution, the presence of calcium channel blocking agents, or the divalent cation ionophore antibiotic A23187. No evidence could be found that entry of calcium ions into the cell has a major role in the sensory adaptation.
Activity of an identified histaminergic neuron, and its possible role in arousal of feeding behavior in semi-intact Aplysia
Authors: Weiss KR , Chiel HJ , Koch U , Kupfermann I
Published: March 2018

The possible functions of histaminergic neuron C2 were studied in an isolated head preparation from which it was possible to obtain intracellular recordings while the buccal mass exhibited feeding-like responses. Application of food to the lips of the isolated head preparation elicited rhythmic buccal movements that appeared to be ingestion responses, since they moved seaweed into the buccal cavity and towards the esophagus, and their frequency and regularity was similar to the ingestion responses studied in a group of intact animals. The ingestion responses of the buccal mass consisted of 2 main phases of movement of the radula from a middle rest position: forward and return to rest, and backward and return to rest. The relative magnitudes and timing of these 2 phases were variable. Intracellular recordings from C2 in the isolated head revealed that C2 is silent when the buccal mass is quiescent, but that it can be excited into spike activity, either by mechanical stimulation of the perioral zone or by chemostimulation that results in rhythmic movement. C2 fires a burst of spikes in phase with each protraction-retraction cycle, and, if the movements continue, C2 fires even when the eliciting stimulus has been removed. Activity of the cell was usually preceded by fast depolarizing responses that appeared to be blocked axon spikes. The evidence suggests that C2 is part of a positive feedback loop that may help maintain the persistence of arousal of feeding behavior beyond the time that food stimuli are removed.
Dual peroxidase and colloidal gold-labeling study of angiotensin converting enzyme and angiotensin-like immunoreactivity in the rat subfornical organ
Authors: Pickel VM , Chan J , Ganten D
Published: March 2018

The cellular relationships between angiotensin converting enzyme (ACE) (EC 3.4.14.1) and angiotensin-like immunoreactivity (AGLI) were examined in the subfornical organ (SFO). Brains from adult rats were fixed by vascular perfusion with 3.75% acrolein and 2% paraformaldehyde. The region containing the SFO was then sectioned on a vibrating microtome. Partially permeabilized sections were immunocytochemically labeled using the peroxidase-antiperoxidase (PAP) or combined PAP and immunogold methods. Goat antiserum to ACE was localized to both non-neuronal and neuronal cells within the SFO. Intense peroxidase immunoreactivity for ACE was associated with the ventricular and basal surface of ependymal cells, the luminal surface of the vascular endothelium, portions of glial membranes exposed to extracellular spaces, and membranous organelles within neuronal processes. Two antisera raised in rabbits against angiotensin II showed peroxidase immunoreactivity within the extracellular spaces and throughout the cytoplasm of numerous axon terminals and a few perikarya and dendrites in the SFO. Axon terminals and dendrites also showed aggregates of AGLI in smooth membranes and vesicles near the plasmalemma. Gold labeling for AGLI was evident in only 6% of the axon terminals and in a smaller number of dendrites containing peroxidase immunoreactivity for ACE. The low incidence of terminals containing both markers appeared to at least partially reflect limited penetration of the 10 nm gold particles. These results provide the first ultrastructural evidence that ACE is associated with the plasmalemma and membranous organelles strategically located for interaction with precursors of angiotensin II or other peptides within the cerebrospinal fluid, extracellular spaces and neurons of the SFO.
Actions of opioids on primate spinothalamic tract neurons
Authors: Willcockson WS , Kim J , Shin HK , Chung JM , Willis WD
Published: March 2018

The effects of iontophoretically applied opiates were tested on 24 spinothalamic tract cells in 12 anesthetized monkeys. The drugs used were chosen because of their agonist actions on different classes of opiate receptors (mu, morphine; kappa, dynorphin; delta, methionine enkephalinamide; sigma, N-allylnormetazocine or SKF 10047 and phencyclidine). The actions of the opiate drugs were generally inhibitory, although excitatory or mixed effects were sometimes seen, especially with morphine and dynorphin. Drug effects could change, depending on the position of the iontophoretic electrode array or on the current employed. Naloxone sometimes antagonized the action of the opiate drugs used, but naloxone did not seem to be a drug suited for iontophoretic application. A number of explanations are discussed to explain the variable actions of the opiate drugs.
Nucleus basalis involvement in conditioned neuronal responses in the rat frontal cortex
Authors: Rigdon GC , Pirch JH
Published: March 2018

Rat frontal cortex neurons exhibit alterations in firing in response to a 2 sec tone cue followed by rewarding medial forebrain bundle (MFB) stimulation. Nucleus basalis neurons supply up to 75% of the cortical cholinergic innervation. The nucleus basalis and ACh have been implicated as playing a role in cognitive function. Three experiments were designed to test the hypothesis that the nucleus basalis cholinergic system is involved in the generation of conditioned neuronal responses in the rat frontal cortex. Local microinjection of the cholinergic antagonist, atropine, into the frontal cortex suppressed the conditioned responses of 22 of 25 cortical single units. Unilateral kainic acid lesioning of the nucleus basalis resulted in a significant decrease in the proportion of units exhibiting conditioned responses in the cortex ipsilateral to the lesion (25%) compared to the proportion of responding units from the cortex of untreated animals (70%). When the firing rates of units encountered in the region of the nucleus basalis were monitored during presentation of the cue-MFB paradigm, 28 of 38 unit recordings exhibited significant increases or decreases in firing rate. Therefore, the results of the experiments indicate that the nucleus basalis cholinergic neurons are involved in the generation of conditioned neuronal responses in the rat frontal cortex.
Changes in tonicity of perfusion medium cause prolonged opening of calcium channels of the rat chromaffin cells to evoke explosive secretion of catecholamines
Authors: Wakade AR , Malhotra RK , Sharma TR , Wakade TD
Published: March 2018

Secretion of catecholamines (CA) from the isolated rat adrenal gland during and after perfusion with hypertonic Krebs bicarbonate solution was studied. Perfusion with hypertonic solution made by adding either 156 mM sodium chloride, choline chloride, arginine hydrochloride, sodium thiocyanate, or 312 mM sucrose had no effect on the spontaneous secretion of CA. The secretion evoked by splanchnic nerve stimulation (10 Hz for 30 sec) and nicotine (2 micrograms) remained unaffected during perfusion with hypertonic Krebs solution (156 mM excess NaCl). After perfusion of the adrenal gland with hypertonic Krebs solution for 1 hr, if the medium was switched to normal Krebs solution the secretion of CA increased from about 15 to 450 ng; it remained elevated for over 1 hr and eventually returned to the control level after 150 min. Secretion of CA obtained in normal Krebs solution after perfusion of the adrenal gland with hypertonic medium was not affected by atropine plus hexamethonium, splanchnectomy, or tetrodotoxin. After perfusion of the adrenal gland with Ca-free hypertonic (275 mM NaCl) Krebs solution for 1 hr, if the medium was changed to normal Krebs solution the secretion of CA increased from 10 to about 4000 ng in the first 10 min. The enhanced secretion was associated with an almost 70% reduction in the CA content of the adrenal medulla. A massive secretion of CA obtained after switchover from hypertonic to normotonic solution was not associated with an increase in lactate dehydrogenase content in the perfusate, nor was there any reduction in the lactate dehydrogenase content of the adrenal medulla. Immediately after the switchover from hypertonic to normotonic medium, the accumulation of Ca45 increased 6- fold over the control accumulation. The increase in Ca45 accumulation was detected as late as 120 min after the switchover, and was accompanied by an increase in the secretion of CA. The most likely explanation for these findings is that Ca channels, once opened after the switchover, inactivate very slowly and allow Ca ions to flow inside the chromaffin cells. The accumulation of tetraphenylphosphonium (C14- TPP), a marker for the membrane potential, was 86 pg/mg in the adrenal medulla perfused with normal Krebs solution, and decreased to 32 pg/mg in the presence of 55 mM K-Krebs solution. After perfusion with hypertonic medium, the accumulation of C14-TPP increased to about 190 pg/mg. Reperfusion with normal Krebs solution decreased the accumulation to about 105 pg/mg. The increase in C14-TPP accumulation observed in hypertonic medium was prevented by inclusion of 30 mM K in the medium.(ABSTRACT TRUNCATED AT 400 WORDS)
Increased presynaptic ATP levels coupled to synaptic activity at the crayfish neuromuscular junction
Authors: Lindgren CA , Smith DO
Published: March 2018

Levels of ATP and related adenylates were measured in the terminal region of efferent nerves in the crayfish opener muscle using the luciferin-luciferase method. Following 1 min of stimulation at 50 Hz, the average (+/- SE) ATP content rose from 13.4 (+/- 1.5) to 19.0 (+/- 2.1) nmol/mg dry weight. The amounts of ADP, AMP, and the phosphagen phosphoarginine did not change significantly. Thus, the increased ATP was not derived from any of these potential sources. The increase was found to depend on synaptic activation, however, for its magnitude was directly related to the concentration of extracellular Ca2+, and it was blocked when CoCl2, verapamil, ruthenium red, or gamma-methylglutamate and picrotoxin were added to the bath. Addition of ATP to the bath solution also increased nerve ATP levels. Based upon measurements of sucrose distribution, only 50% of this increase was in the extracellular water space. The remainder of the ATP had either entered the nerve, become adsorbed extracellularly, or both. Addition of 2- deoxy-D-glucose and gamma-32P-ATP to the bath resulted in the formation of 32P-2-deoxy-D-glucose-6-P by the nerve. This suggests that a fraction of the extracellular ATP does enter the neuron chemically intact. To determine whether exogenous ATP is the source of the increased ATP measured in the nerve following stimulation, the bath was assayed for ATP. Stimulation did cause ATP levels to increase significantly; however, the maximum concentration was 3 orders of magnitude lower than that required to increase ATP levels in resting nerve.(ABSTRACT TRUNCATED AT 250 WORDS)
Dual-component synaptic potentials in the lamprey mediated by excitatory amino acid receptors
Authors: Dale N , Grillner S
Published: March 2018

The synaptic mechanisms underlying amino acid-mediated excitation in the lamprey spinal cord have been investigated. Fine stimulating electrodes were used to stimulate single axons in the spinal cord and evoke unitary EPSPs in lamprey motoneurons and one type of premotor interneuron, the CC interneuron. Three types of EPSP, distinguished by their time course and sensitivity to amino acid antagonists, were seen. Fast EPSPs had a fast rise time (mean, 6.5 msec) and a short half-decay time (mean, 22.5 msec). Slow EPSPs lasted at least 200 msec, had a slow rise time (mean, 28 msec), and a long half-decay time (mean, 109 msec). The third type of unitary potential, called “mixed” EPSP, also lasted at least 200 msec, had a fast rise time (mean, 12 msec), and a long half-decay time (mean, 105 msec). Lamprey neurons were found to possess 3 types of excitatory amino acid receptor: N-methyl-D-aspartate (NMDA), kainate, and quisqualate receptors. 2-Amino-5-phosphonovaleric acid (APV) or Mg2+ blocked the depolarizations caused by N-methyl-D,L- aspartate (NMA) but not those of kainate or quisqualate. Cis-2, 3- piperidine dicarboxylic acid (PDA) blocked the depolarizations caused by NMA and kainate but not those of quisqualate. Fast EPSPs were unaffected by the bath application of APV or Mg2+ but were greatly reduced by PDA, suggesting that these EPSPs were mediated by non-NMDA, possibly kainate receptors. Both APV and Mg2+ blocked the slow EPSPs, suggesting that they were mediated by NMDA receptors.
Selective innervation of transplanted limb muscles by regenerating motor axons in the axolotl
Authors: Wigston DJ
Published: March 2018

The segmental pattern of motor innervation of hindlimb muscles in the axolotl was studied before and after reinnervation. To ascertain the specificity of reinnervation, the four spinal nerves innervating the hindlimb were severed and allowed to regenerate. The segmental origin of axons reinnervating particular muscles was then determined by intracellular recording from muscle fibers. Muscles were reinnervated in a specific manner: From the outset, the axons reinnervating each muscle originated largely from segmentally appropriate spinal nerves in the proper proportions, suggesting that a reliable mechanism of selective synapse regeneration exists even in mature axolotls. To examine the selectivity of reinnervation, individual muscles were transplanted to novel positions within the limb and the specificity of their reinnervation determined. Even after being moved to new positions, muscles were reinnervated for the most part by axons of appropriate segmental origin. Therefore, cues must exist on or within limb muscles that regenerating motor axons recognize and use to discriminate between different muscles during synapse formation. These results suggest that one of the mechanisms that promote the reestablishment of correct connections during reinnervation of axolotl limbs may be the selective formation of synapses with appropriate target cells.
The contribution of GABA-mediated inhibitory mechanisms to visual response properties of neurons in the kitten's striate cortex
Authors: Wolf W , Hicks TP , Albus K
Published: March 2018

The effect of the microiontophoretic administration of the GABA antagonist bicuculline methiodide (BMI) on the responses of striate cortical neurons to light stimulation was investigated in kittens ranging in age between 11 and 28 d. The orientation sensitivity of the majority of the 88 neurons tested for this parameter decreased (40%) or was eliminated (18%) following the administration of BMI. Changes were seen in all layers and in all neuronal types, and the proportions of neurons that changed their orientation specificity were about the same during the second, third, and fourth postnatal weeks. Twenty-eight percent of the neurons were not affected in their orientation sensitivity by BMI. These neurons were recorded at all postnatal ages; they were located preferentially in layers IV and VI; and they had unimodal, bimodal, or ON-OFF mixed receptive fields. The remaining 14% of the neurons were initially unresponsive or responded in an erratic way to visual stimulation. These neurons became responsive and even exhibited orientation-specific responses during administration of BMI. The majority (56%) of direction-specific neurons became direction- nonspecific after the administration of BMI. Seventeen percent preserved some direction specificity, whereas 27% did not show any change at all. The effects of BMI on direction sensitivity were seen at all postnatal ages and on all neuronal types throughout layers III-VI. The majority of neurons unaffected by BMI in their direction sensitivity resided in layer VI. In those cases where orientation sensitivity was reduced, direction sensitivity (if present) was usually diminished as well. However, some neurons were found in which only 1 of the 2 parameters was significantly changed by BMI. The spatial structure of the receptive field, as revealed by stationary stimulation, was changed significantly by BMI in about half the neurons tested. A straightforward correlation between the alteration of orientation and/or direction sensitivity and changes in receptive-field structure was not found. The results demonstrate that, in the immature striate cortex, receptive-field properties of many neurons are determined by inhibitory processes mediated by GABA, which may also dictate the actual visual responsiveness of the neurons. The dissociations in the effects of BMI on orientation sensitivity, direction sensitivity, and receptive-field substructure indicate that the synaptic organization responsible for the various functional parameters is unlikely to be the same.
Expression of the jimpy gene in the spinal cords of heterozygous female mice. I. An early myelin deficit followed by compensation
Authors: Bartlett WP , Skoff RP
Published: March 2018

The jimpy mutation results in severe hypomyelination throughout the CNS of hemizygous male mice. In the female carrier of the jimpy gene, partial hypomyelination is predicted as a consequence of genetic mosaicism resulting from random X-chromosome inactivation. The spinal cord of the female carrier was studied morphologically to determine if hypomyelination is present, the manner in which a possible myelin deficit is expressed, and the extent, if any, of compensation. The spinal cords of 14- to 15-d-old heterozygotes were found to be hypomyelinated. A deficit of 31% in the amount of myelin as compared to controls was detected in these young carriers by point-counting stereology. By the end of the first month the deficit was 12%, and after the fifth month complete recovery had occurred. These results demonstrate that the neuroglial cells are capable of compensating totally for the jimpy defect over a several month period. The reduction in the amount of myelin at 2 weeks postnatally is due to the ensheathment of fewer axons than normal and the formation of myelin sheaths that are thinner than normal. It is not due to a significant reduction in amount of axoplasm and a corresponding decrease in amount of myelin. This finding indicates that overall brain development is not retarded but that expression of the jimpy gene selectively affects the glial cells. Our morphologic studies also suggest that the neuron is not the target of the jimpy mutation. One line of evidence for this statement is that virtually all the axons are partially ensheathed, a condition that should not occur if 50% of the neurons are defective in the mosaic. The coexistence of both normal and defective cells within the same cell population and the apparent sparing of the neuron makes the female carrier of the jimpy gene an excellent model for studying mechanisms of compensation and plasticity of neuroglial cells.
Oligodendroglial cell death in jimpy mice: an explanation for the myelin deficit
Authors: Knapp PE , Skoff RP , Redstone DW
Published: March 2018

Neuroglial cell death was investigated in 3 white matter tracts of jimpy and normal mice. In normal animals, glial death during development ranged from 0.5 to 2.7% of the total glial population. The number of dying glial cells was significantly higher in jimpy animals at times corresponding with oligodendroglial proliferation and the onset of myelination in each tract. At certain ages, over 10% of the glial population were pyknotic at the light-microscopic level. Dying glial cells that were identified ultrastructurally presented the characteristics of oligodendrocytes. Premature death of oligodendrocytes presents a simple explanation for the gross deficits of myelin in jimpy animals. The shortened life span of the jimpy oligodendrocyte may preclude the elaboration of a normal myelin sheath. The jimpy model may prove to be a valuable tool in delineating a role for normal neuroglial cell death during the development of the nervous system.
Protein complexity of central nervous system cell lines
Authors: Schubert D , Brass B , Dumas JP
Published: March 2018

The total extracellular proteins and the most abundant 960 intracellular proteins of clonal CNS nerve and glial cell lines were examined by quantitative 2-dimensional acrylamide gel electrophoresis. While less than 0.2% of the intracellular proteins differ among the 5 nerve and 4 glial cell lines studied, over 65% of the extracellular proteins vary in distribution between the 2 major classes of CNS cells. These data indicate that the phenotypic complexity of nerve and glia populations is similar and that most of the protein complexity is in extracellular molecules.
Interspecies selective motoneuron projection patterns in chick-quail chimeras
Authors: Tanaka H , Landmesser LT
Published: March 2018

During normal development chick motoneurons have been shown to project selectively to appropriate muscles by responding to a series of cues, both specific and nonspecific, within the limb. We tested the ability of motoneurons from another avian species, the Japanese quail, to respond to these cues by transplanting chick limb buds onto quail embryos and quail limb buds onto chick embryos between stages 17 1/2 and 19. Feulgen staining, which distinguishes chick from quail cells on the basis of nuclear chromatin, revealed that all limb tissue, including muscle, was of donor origin, indicating that the migration of somite-derived muscle precursor cells had been completed by the time of transplantation. Normal quail motoneuron pools for most muscles were located in the same relative positions as homologous chick pools. In chick-quail chimeras we found that the motoneuron pools of one species selectively innervated the homologous muscles in the limb of opposite species with considerable precision. This was determined by defining the segmental innervation pattern of the muscles electrophysiologically and by retrogradely labeling motoneuron pools with HRP. Selective innervation was confirmed by using the functional activation patterns of the motoneuron pools as an additional means of identifying motoneurons. We conclude that any limb-derived cues required by motoneurons to project to their appropriate muscles must be similar in chick and quail and that the growth cones of both species must have similar detector systems for responding to these cues. Only 7 spinal segments were found to innervate the quail limb (versus 8 for the chick), resulting in an anterior shift in the spinal segments innervating several posterior quail muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
Forward and backward classical conditioning of the flexion reflex in the spinal cat
Authors: Durkovic RG , Damianopoulos EN
Published: March 2018

Effects of forward and backward conditioned-unconditioned stimulus (CS- US) intervals on classical conditioning of the flexion reflex were examined in a cat spinal preparation. Interstimulus intervals (ISIs) ranging from +3.0 to -3.0 sec were employed in 9 experimental groups and the results compared with those of an explicitly unpaired control group. Forward conditioning produced an asymmetrical, inverted U-shaped gradient relating magnitude of conditioning to ISI for both acquisition and extinction. The optimum ISI was 1.0 sec. Backward ISIs also produced excitatory conditioning, with optimal conditioning at -0.25 sec. Unlike forward conditioning, backward conditioning produced little sign of retention during extinction trials. The results, which parallel in several ways those of ISI effects in studies of intact animals, support the hypothesis that backward and forward conditioning may be fundamentally different phenomena, under the control of different neural processes.
Connectional basis for frequency representation in the nuclei of the lateral lemniscus of the bat Eptesicus fuscus
Authors: Covey E , Casseday JH
Published: March 2018

To study the role of the lateral lemniscus as a link in the ascending auditory pathway, injections of neuronal tracers were placed in the anteroventral cochlear nucleus (AVCN) and in the inferior colliculus of the bat Eptesicus fuscus. To correlate the anatomical results with tonotopic organization, the characteristic frequency of cells at each injection site was determined electrophysiologically. Pathways from AVCN diverge to 3 major targets in the lateral lemniscus, the intermediate nucleus and 2 divisions of the ventral nucleus (VNLL). Projections from these 3 nuclei then converge at the inferior colliculus. One cell group is particularly notable for its cytoarchitectural appearance. It is referred to here as the columnar area of VNLL because its cells are organized as a tightly packed matrix of columns and rows. The connections of the columnar area are organized in sheets that are precisely related to the tonotopic organization of both AVCN and the inferior colliculus. Sheets of cells in the dorsal part of the columnar area receive projections from low-frequency parts of AVCN and project to low-frequency parts of the inferior colliculus. These sheets of connections occupy successively more ventral locations as the tonotopic focus of the injection site increases in frequency. The entire range of frequencies audible to the bat is systematically represented along the dorsal-ventral dimension of the columnar area. Because each column is only 20–30 cells in height, frequency representation must be compressed in this dimension. Within the columnar area there is an overrepresentation of frequencies between 25 and 50 kHz, which corresponds roughly to the range of the FM echo- location call in Eptesicus. The connections of the other nuclei of the lateral lemniscus are not as precisely related to the tonotopic organization of the system as are those of the columnar area.
The appearance of an L1-like molecule in the chick primary visual pathway
Authors: Lemmon V , McLoon SC
Published: March 2018

A monoclonal antibody, 8D9, has been obtained that binds to axons in the chick nervous system. Biochemical and immunological experiments indicate that the 8D9 antigen is related to the mouse L1 cell-adhesion molecule. The results of immunohistochemical experiments using monoclonal antibody 8D9 to study the development of the chick visual system are consistent with the 8D9 antigen functioning in axon fasciculation.