bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurite outgrowth in molluscan organ and cell cultures: the role of conditioning factor(s)
Authors: Wong RG , Hadley RD , Kater SB , Hauser GC
Published: March 2018

Isolated neurons from adult central ganglia of the snail Helisoma were cultured in vitro in modified Liebowitz L-15 medium. Such neurons displayed electrical excitability comparable to that in acutely dissected ganglia. Isolated neurons remained spherical in defined medium throughout culture durations up to 2 weeks. This static morphology was contrasted by the significant neuritic outgrowth which occurred from neurons maintained in medium with co-cultured intact Helisoma brains or in brain conditioned medium. A morphological sequence of growth cone formation and neurite extension occurred only in the presence of a conditioning factor(s) with a mode of action which included tight binding of the conditioning factor to the substratum. Under these conditions, the two primary neuronal phenotypes, electrical excitability and complex neuronal architecture, could be affected independently in adult molluscan neurons cultured in vitro.
Depolarization-induced synaptic plasticity at cholinergic synapses in tissue culture
Authors: Fishman MC , Nelson PG
Published: March 2018

Many synaptic connections are rejected during development, and the remainder are stabilized. Whether neuronal activity is important in this remodeling remains unknown. Cholinergic synapses are formed in tissue culture between the hybrid NG108–15 (neuroblastoma X glioma) cell and skeletal myotubes. We have investigated changes in these synapses brought about by chronic depolarization. Most myotubes are innervated under control conditions and recording from a myotube while stimulating a neighboring hybrid cell demonstrates that most hybrid- myotube pairs in anatomical proximity also are connected synaptically. Multiple innervation of one myotube by several hybrid cells is common. After 24 to 72 hr of cell depolarization with low concentrations of veratridine, myotubes continue to evidence synaptic activity, but the chance of evoking activity, in a given myotube by stimulation of a neighboring hybrid cell, is diminished to 30% of control values; only 5% of myotubes can be demonstrated to still have multiple innervation. However, the efficacy of synapses that persists after veratridine exposure is comparable to control. By 24 hr after removal of veratridine, synapse number returns to control levels. Tetrodotoxin prevents these effects. We suggest that components responsible for the well known development change from polyneuronal to mononeuronal innervation may be present and accessible to manipulation in this relatively well defined tissue culture system.
Relation between cell size and response characteristics of vestibulospinal neurons to labyrinth and neck inputs
Authors: Boyle R , Pompeiano O
Published: March 2018

(1) The activity of 136 Deiters' neurons projecting to lumbosacral segments of the spinal cord has been recorded in decerebrate, partially cerebellectomized cats, and their response characteristics to sinusoidal stimulation of labyrinth and neck receptors have been related to cell size inferred from the conduction velocity of the corresponding axons. (2) Vestibulospinal neurons with faster conduction velocity and, by inference, having thicker axons and larger cell bodies differed from those neurons having lower axonal conduction velocity by displaying (i) a relatively irregular interspike interval distribution; (ii) a lower resting discharge rate; (iii) a periodically modulated response to the labyrinth input elicited by sinusoidal tilt around the animal's longitudinal axis (0.026 Hz, 10 degrees) characterized by an increase in firing rate during side-down roll tilt; (iv) an increase in gain (impulses per sec per degree) and phase lag relative to the displacement of the labyrinth response to increasing angular acceleration; (v) a greater gain in labyrinth than neck input, the latter elicited by sinusoidal neck rotation (0.026 Hz, 5 or 10 degrees); and (vi) due to the imbalance of the gains of the separate labyrinth and neck responses and their predictable vectorial summation, a response to both inputs elicited by head rotation resembling that obtained by labyrinth stimulation alone. (3) These findings are discussed in terms of the reciprocal distribution of synaptic contacts of vestibular and neck afferents on vestibulospinal neurons as a function of cell size. The evidence indicates that, in addition to intrinsic neuronal properties related to cell size, the quantitative and qualitative organization of synaptic inputs represents the critical factor controlling the responsiveness of vestibulospinal neurons.
Stretch-induced contraction of intrafusal muscle in cat muscle spindle
Authors: Poppele RE , Quick DC
Published: March 2018

Measurements of tension, stiffness, and sarcomere length of intrafusal muscle during ramp stretch of isolated muscle spindles have revealed a stretch-induced contraction of the bag1 fiber. This behavior can account for the very high sensitivity of primary endings to stretch as well as the enhanced sensitivity evoked by dynamic fusimotor stimulation.
Notexin preferentially inhibits the release of newly synthesized acetylcholine from rat brain synaptosomal fractions
Authors: Gundersen CB , Jenden DJ
Published: March 2018

An investigation was made of the effects of the snake venom neurotoxin, notexin, on acetylcholine turnover in rat brain P2 fractions using a gas chromatographic mass spectrometric assay for acetylcholine and choline. In contrast to earlier reports, we found a stimulation of the uptake and acetylation of labeled choline by toxin-treated P2 fractions. More significantly, notexin inhibited the release of this newly synthesized transmitter. These effects were found to be dependent on the dose of the toxin and the time of exposure of the P2 fraction to notexin. Longer exposure to notexin or experiments involving resuspension of notexin-treated P2 fractions appeared to result in considerable lysis of the transmitter-containing particles. Thus, notexin may alter acetylcholine compartmentation in the nerve ending and thereby affect acetylcholine synthesis.
The influence of gonadectomy, androgen exposure, or a gonadal graft in the neonatal rat on the volume of the sexually dimorphic nucleus of the preoptic area
Authors: Jacobson CD , Csernus VJ , Shryne JE , Gorski RA
Published: March 2018

Although the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of the adult rat has been shown to be modified by the hormone environment early in postnatal life, the present study was performed to clarify several fundamental questions related to this process. This study was designed to evaluate the ability of exogenous testosterone propionate (TP), or a gonadal graft, to influence SDN-POA volume in rats which were gonadectomized as neonates. Orchidectomy on day 1 resulted in an approximately 50% decrease in adult SDN-POA volume; however, the influence of the testes on their resulting SDN-POA volume was replaced affectively by the administration of 100 micrograms or 1 mg of TP on postnatal day 2 or by a testicular (but not ovarian) graft on the day of castration. In the female, ovariectomy on postnatal day 1 failed to alter SDN-POA volume relative to that of sham-operated females. Exogenous TP, but neither testicular nor ovarian grafts, resulted in a larger SDN-POA volume when observed in the adult female. Thus, the development of the SDN-POA of the neonatal male is significantly influenced by the hormonal activity of the testes at this time period. While the SDN-POA of the neonatal female is potentially responsive to androgen, the role played by the ovaries in the development of the SDN-POA remains unclear. In addition, the different response of the developing male and female SDN-POA to a testicular graft suggests that the hormonal sensitivity of this nucleus may differ in the two sexes.
Dopamine metabolism following irreversible inactivation of aromatic amino acid decarboxylase in retina
Authors: Parkinson D , Baughman R , Masland RH , Rando RR
Published: March 2018

The effects of an intravitreal injection of alpha-fluoromethyldopa, an irreversible mechanism-based inactivator of aromatic-L-amino acid decarboxylase, on the retinal dopamine content of light-adapted chicks and rabbits have been examined. A single administration of 10 nmol of alpha-fluoromethyldopa totally inactivates aromatic L-amino acid decarboxylase within 2 hr in vivo in rabbits. By 4 to 6 hr, the level of dihydroxyphenylalanine increased 7-fold and the levels of dopamine and dihydroxyphenylacetic acid fell by 90%. With an injection of 50 nmol, similar results were observed in chicks. The levels of dihyroxyphenylacetic acid began to fall soon after injection when significant (30 to 40%) amounts of dopamine were still present. These results are discussed in relation to the use of tissue dihydroxyphenylacetic acid levels to indicate the level of dopaminergic neuronal activity or dopamine synthesis. Recovery by the retinae of both species was shown by the return of aromatic L-amino acid decarboxylase activity and the resynthesis of dopamine.
Evidence for a neurotransmitter role for 5-hydroxytryptamine in chick retina
Authors: Parkinson D , Rando RR
Published: March 2018

Evidence to support a neurotransmitter role for 5-hydroxytryptamine in chick retain is presented. Putative 5-hydroxytryptophan and 5- hydroxytryptamine extracted from chick retina have been characterized chromatographically and electrochemically and have been found to behave like the authentic compounds. Retinal tryptophan hydroxylase activity could not be demonstrated in vitro, but chick retina was able to synthesize 5-[3H]hydroxytryptamine from [3H]tryptophan in vivo. Retinal 5-hydroxytryptamine levels were reduced by local injection of alpha- fluoromethyldopa, an inhibitor of aromatic L-amino acid decarboxylase, or reserpine, indicating that his amine is both synthesized and stored in this tissue. The retinae of light-adapted chicks have higher levels of 5-hydroxytryptamine and its major metabolite, 5-hydroxyindoleacetic acid, than dark-adapted animals. The turnover of 5-hydroxytryptamine appears to be greater in the light after inhibition of synthesis. Conversely, the rate of synthesis of 5-hydroxytryptamine appears to be greater in the dark. The possible interaction of dopaminergic neurons and the 5-hydroxytryptamine-containing cells and the effect of alpha- fluoromethyldopa on this relationship are discussed. The data lend support to the notion that 5-hydroxytryptamine in chick retina may have a neurotransmitter function.
Characterization of abnormalities in the visual system of the mutant mouse pearl
Authors: Balkema GW , Pinto LH , Drager UC , Vanable JW
Published: March 2018

Mice of the mutant strain pearl (pe/pe) differ from the wild strain by a single gene mutation, which leads to a lightening of the coat color. We tested this strain to see if this mutant gene also expressed itself in one or more visual abnormalities. Pearl mice were found to lack totally the optokinetic nystagmus reflex that was present in every normal mouse that we examined. This lack of optokinetic nystagmus was not due to oculomotor defects, since postrotatory nystagmus was normal. As described for other pigmentation mutants, we found that pearl mutants had a reduced ipsilateral projection to the lateral geniculate nucleus, superior colliculus, and visual cortex. We recorded from single cells in the superior colliculus and found response properties and light sensitivities to be normal over the luminance range at which optokinetic nystagmus was tested. However, at very dim backgrounds (scotopic levels), the incremental sensitivities of these cells in pearl mice were about 100 times lower than those of normal mice. This reduction in sensitivity was restricted to scotopic backgrounds and was not due to abnormalities in either the time course of dark adaptation or the receptive field sizes of single cells. In recordings of the electroretinographic response, both the waveforms and the normalized magnitudes of the A and B waves of pearl were indistinguishable from those of normal mice, which seems to indicate that the cause of pearl's sensitivity defect is located central to the main electrical events in the photoreceptors. The normality of many aspects of the visual system of pearl mice contrasts sharply with the complete absence of optokinetic nystagmus, with the reduced ipsilateral projection, and with the reduced dark sensitivity of the cells in the superior colliculus.
Loss of muscarinic receptors and of stimulated phospholipid labeling in ibotenate-treated hippocampus
Authors: Fisher SK , Frey KA , Agranoff BW
Published: March 2018

The stimulation of phospholipid labeling by muscarinic agonists has been examined in nerve ending preparations from lesioned hippocampus in order to investigate the synaptic locus of the effect. Unilateral injections of the neurotoxin, ibotenic acid, into the hippocampus resulted in an extensive loss of nerve cells from both the dentate gyrus and hippocampus on the lesioned side and a parallel loss of muscarinic receptors as revealed by [3H]quinuclidinyl benzilate autoradiography. Homogenates and nerve ending fractions prepared from the lesioned side of the hippocampus possessed a reduced specific activity (expressed per milligram of protein) of glutamic acid decarboxylase as well as a reduced number of muscarinic receptors compared with the control side. By contrast, choline acetyltransferase activity was either unchanged or slightly increased on the lesioned side. Although there was a reduced yield (25%) of nerve endings from the lesioned side, the specific activity of 32Pi incorporation into phospholipids in the absence of added carbachol was comparable to that of the control side. There was, however, a marked reduction in the carbachol stimulation of phosphatidic acid and phosphatidylinositol labeling in nerve ending fractions obtained from he lesioned hippocampus. These results indicate that the muscarinic receptors present in nerve ending fractions from hippocampus and implicated in stimulated phospholipid turnover are derived from cholinoceptive intrinsic neurons.
Correlative firing patterns of serotonergic neurons in rat dorsal raphe nucleus
Authors: Wang RY , Aghajanian GK
Published: March 2018

In this study, local neuronal interactions in the midbrain dorsal raphe nucleus (DRN) were analyzed by the use of autocorrelation and cross- correlation histograms. The autocorrelograms of serotonin (5- hydroxytryptamine; 5-HT)-containing cells showed an initial trough and subsequent periodicity which corresponded to their regular rhythmic firing pattern. Cross-correlograms revealed that all adjacent 5-HT neurons recorded from single micropipettes displayed complicated patterns of functional interactions. The interactions could be grouped into the following categories: (1) synchronization (interspike intervals less than 10 msec), (2) synchronization and direct inhibition, (3) synchronization and mutual inhibition. In contrast, cross-correlograms generated from adjacent neuronal pairs consisting of one 5-HT cell and one non-5-HT neuron or from non-adjacent 5-HT neuronal pairs usually failed to show functional interactions. The results of the present study are consistent with previous findings of a powerful auto-and mutual regulatory system for 5-HT neurons in the DRN.
Immunostaining of neurofibrillary tangles in Alzheimer's senile dementia with a neurofilament antiserum
Authors: Dahl D , Selkoe DJ , Pero RT , Bignami A
Published: March 2018

Using anti-chicken brain neurofilament antisera, Alzheimer's neurofibrillary tangles from two patients with senile dementia were stained by immunofluorescence and by the peroxidase-antiperoxidase procedure in cryostat sections of hippocampus and frontal cortex. In sections of cerebellum obtained from the same patients, the distribution of immunostaining was the same as that observed in experimental animals: Purkinje cell baskets and nerve fibers in the inner half of the molecular layer were demonstrated selectively. The immunostaining of the tangles was abolished when the antisera were absorbed by their own antigen, by bovine brain filament preparations, or by the fraction of bovine brain filament preparations nonabsorbed on anti-glial fibrillary acidic (GFA) protein immunoaffinity columns. Absorption with a bovine microtubule preparation isolated by two cycles of the assembly-disassembly procedure did not abolish the staining. Immunostaining experiments conducted on bovine brain filament preparations resolved on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the antisera staining the tangles reacted with the 200,000-, 150,000-, and 70,000-dalton neurofilament polypeptides. Antisera raised to the 150,000- dalton bovine neurofilament polypeptide isolated by sodium dodecyl sulfate- polyacrylamide gel electrophoresis stained the tangle much less intensely, although Purkinje cell baskets in the cerebellum appeared well stained. No staining of neurofibrillary tangles was observed with antisera to other classes of 10-nm filament proteins (GFA protein, vimentin, and desmin).
Inverse relationship between transmitter release and terminal length in synapses on frog muscle fibers of uniform input resistance
Authors: Nudell BM , Grinnell AD
Published: March 2018

Transmitter release at frog neuromuscular junctions is known to be related positively to nerve terminal length. However, the correlation is inexact, with a wide scatter of data. We have analyzed the endplate potentials (EPPs) of identified frog cutaneous pectoris muscle fibers, correlating release with terminal size and fiber input resistance (Rin). Transmitter release was assayed by quantal analysis of endplate activity in low Ca2+ Ringer solution and by measurement of the EPPs evoked in normal Ringer solution and curare. For fibers of approximately the same Rin, there is an inverse relationship between the level of transmitter release per unit length and total terminal length. Terminals with high levels of release per unit length tend to be shorter than do those which release relatively less transmitter per unit length. Furthermore, if the analysis is restricted similarly to fibers with nearly identical Rin, the total transmitter release of the largest endplates is usually less than that of the shorter terminals in the sample. These findings do not contradict the overall trend of greater release and longer terminals on larger muscle fibers (with lower Rin). Instead, they help explain the variability in measurement of release versus terminal length. The relationship that we find is consistent with the hypothesis that, in the cutaneous pectoris, terminals are induced to grow until an adequate safety factor for transmission is achieved.
Pseudopodial interdigitations between abutted nerve terminals: diffusion traps which occur in several nuclei of the rat limbic system
Authors: Boyne AF , Tarrant SB
Published: March 2018

Stimulation of the Torpedine ray electric organ can cause the loss of synaptic vesicles and the growth of pseudopodia from the nerve terminals (Boyne, A. F., and S. McLeod (1979) Neuroscience 4: 615–624). The latter embed themselves in corresponding indentations in abutted terminals. The geometry of these pseudopodial indentations (PSIs) can vary: (i) in length, (ii) in the extent of constriction of the base, and (iii) through a compound interaction between different pseudopodia extending in opposite directions. Examination of six rat brain nuclei in the limbic system has shown that their neuropil can be categorized according to the prevalence of either (i) nerve terminals indented by nerve terminal outgrowths (i.e. PSIs) or (ii) nerve terminals indented by dendritic outgrowths: these have been previously termed spinules. Clusters of simple PSIs were seen in the central nucleus of the amygdala, while base-constricted and compound forms were found in the globus pallidus and substantia nigra. Dendritic spinules were prevalent in the nucleus accumbens and the molecular layer of the hippocampus. In the CA4 hilar region of the hippocampus, large nerve terminals containing PSIs were found. The caudate neuropil appeared to be of mixed character in that the small terminals often had spinules but occasionally showed PSIs. Spinules have been recognized for many years and the possibility of their plasticity has been raised previously (Tarrant, S. B, and A. Routtenberg (1977) Tissue Cell 9: 461–473). The present report appears to be first detailed description of an alternative form of invasion which is known to be plastic in the elasmobranch electric organ. It is suggested that the extracellular space between the partners of a PSI could act as variable diffusion traps. If the involved boutons carry action potentials, then nonsynaptic release and accumulation of substances such as potassium, amino acids, and nucleotides may be expected during stimulation. Consequent direct or receptor-mediated effects on the membrane potential could influence transmission through adjacent synapses.
Vasopressin augments depolarization-induced release and synthesis of serotonin in hippocampal slices
Authors: Auerbach S , Lipton P
Published: March 2018

Vasopressin may be a neurotransmitter and in vivo experiments suggest that it acts on monoamine metabolism. The rat hippocampal slice contains serotonergic nerve terminals but not cell bodies; we studied the effect of vasopressin on the synthesis and release of serotonin from these nerve terminals during depolarization. Incubation of slices in a buffer containing 60 mM K+ (high K buffer) for 10 min stimulated the release of serotonin into bathing medium and resulted in a Ca2+- dependent depletion of tissue serotonin from about 4.2 to about 2.8 ng/mg of protein. Vasopressin (10(-7) M) inhibited this depletion by about 70% so that serotonin levels fell only to 3.8 ng/mg of protein. The peptide also augmented the high K+-induced release of serotonin into the bathing medium by about 60%. The synthesis of serotonin was measured by determining its accumulation during a period when its catabolism was inhibited by pargyline. Vasopressin augmented the synthesis of serotonin in slices incubated in high K buffer by about 60%. There are serotonergic nerve endings in both the dentate gyrus and CA1 regions of the hippocampus. The effect of vasopressin on tissue serotonin was confined to the dentate gyrus regions. The data show that vasopressin acts on a specific group of hippocampal nerve endings to increase serotonin synthesis. The resulting increase in tissue serotonin may be the factor leading to the observed increase in serotonin release.
Peripheral neural mechanisms of cutaneous hyperalgesia following mild injury by heat
Authors: LaMotte RH , Thalhammer JG , Torebjork HE , Robinson CJ
Published: March 2018

Pain thresholds in humans were determined for heat stimulations of the skin before and after a mild injury induced by a single conditioning stimulus (CS) of 50 degrees C and 100 sec duration. The same stimuli were delivered to the receptive fields of C fiber and A fiber mechanoheat-sensitive nociceptors (CMH and AMH nociceptors, respectively) and of low threshold warm and cold receptors in the anesthetized monkey and to the receptive fields of CMH nociceptors recorded percutaneously from the peroneal nerve of awake humans. Pain thresholds in normal skin were matched only by the response thresholds of CMH and not AMH nociceptors. Immediately following heat injury, some pain thresholds and CMH response thresholds were elevated, but by 5 to 10 min after the CS, pain and CMH thresholds were lowered to 2 to 6 degrees C below normal (hyperalgesia and nociceptor sensitization). No other type of cutaneous receptor studied exhibited changes in threshold similar to those observed for pain and for CMH nociceptors. The magnitude of hyperalgesia in humans and the magnitude of sensitization of CMH nociceptors in monkeys following heat injury were greater for hairy than for glabrous skin. The time course of the development of hyperalgesia was not altered by ischemia or conduction block in A fibers. The results support the conclusion that altered activity in CMH nociceptors is a major peripheral determinant of cutaneous hyperalgesia following a mild heat injury to the skin.
Axonal transport of muscarinic cholinergic receptors in rat vagus nerve: high and low affinity agonist receptors move in opposite directions and differ in nucleotide sensitivity
Authors: Zarbin MA , Wamsley JK , Kuhar MJ
Published: March 2018

The presence and transport of muscarinic cholinergic binding sites have been detected in the rat vagus nerve. These binding sites accumulate both proximal and distal to ligatures in a time-dependent manner. The results of double ligature and colchicine experiments are compatible with the notion that the anterogradely transported binding sites move by fast transport. Most of the sites accumulating proximal to ligatures bind the agonist carbachol with high affinity, while most of the sites accumulating distally bind carbachol with a low affinity. Also, the receptors transported in the anterograde direction are affected by a guanine nucleotide analogue (GppNHp), while those transported in the retrograde direction are less, or not, affected. The bulk of the sites along the unligated nerve trunk bind carbachol with a low affinity and are less sensitive to GppNHp modulation than the anterogradely transported sites. These results suggest that some receptors in the vagus may undergo axonal transport in association with regulatory proteins and that receptor molecules undergo changes in their binding and regulatory properties during their life cycle. These data also support the notion that the high and low affinity agonist form of the muscarinic receptor represent different modulated forms of a single receptor molecule.
The distribution of the cells of origin of callosal projections in cat visual cortex
Authors: Segraves MA , Rosenquist AC
Published: March 2018

The distribution of neurons projecting through the corpus callosum (callosal neurons) was examined in retinotopically defined areas of cat visual cortex. As many callosal neurons as possible were labeled in a single animal by surgically dividing the posterior two-thirds of the corpus callosum and exposing the cut ends of callosal axons to horseradish peroxidase. The distribution of callosal neurons within a visual field representation was related to standard electrophysiological maps as well as to recording sites marked by electrolytic lesions. Callosal neurons were found in every retinotopically defined cortical area. The portion of the visual field representation that contained callosal neurons increased progressively from the area 17/18 border to area 19, to areas 20 and 21, and to the lateral suprasylvian visual areas. In area 17, the portion of the visual field representation containing callosal neurons extended from the vertical meridian out to a maximum of 10 degrees azimuth. In the posteromedial lateral suprasylvian visual area, callosal neurons were present in a region extending from the vertical meridian representation out to a representation of 60 degrees azimuth. Most callosal neurons were medium to large pyramids at the border of layers III and IV. A few layer IV stellates were among the callosal neurons of areas 17 and 18. In area 19 and even more so in the lateral suprasylvian visual areas, callosal neurons included pyramidal and fusiform-shaped cells in layers V and VI. The laminar distributions of callosal neurons in areas 20 and 21 were similar to those of area 19 and the lateral suprasylvian visual areas. The widespread distribution of callosal neurons in areas 20 and 21 and in the lateral suprasylvian visual areas suggests that the regions of peripheral visual field representation in cat cortex, as well as the representations of the vertical meridian, have access to the opposite cerebral hemisphere. This finding is significant in light of demonstrations of the importance of some of these cortical areas in the interhemispheric transfer of visual learning.
Extracts of electric lobe and electric organ from Torpedo californica increase the total number as well as the number of aggregates of chick myotube acetylcholine receptors
Authors: Connolly JA , St. John PA , Fischbach GD
Published: March 2018

Saline extracts prepared from the electric lobe, the electromotor nerves, and the electric organ (the electromotor system) of Torpedo californica increase the number of ACh receptors on uninnervated chick myotubes in culture, while extracts from T. californica liver or skeletal muscle do not. The extracts also increase the ACh sensitivity of treated myotubes, indicating that newly synthesized receptors are functional. The active substance(s) is heat sensitive but not trypsin sensitive. Gel filtration on Bio-Gel P-150 shows that the activity is associated with a peak of low (less than 5,000-dalton) molecular weight activity. Labeling studies with rhodamine-conjugated alpha-bungarotoxin show that, in addition to their effect on receptor number, these extracts also cause aggregation of prelabeled ACh receptors on the myotube surface.
Complete distribution patterns of neurons with characteristic antigens in the leech central nervous system
Authors: Zipser B
Published: March 2018

Monoclonal antibodies were used to map the distribution of neurons in the leech which contain a particular antigen. This technique reveals the genetically determined variation in cell body distribution along the nerve cord. In addition, antibodies also reveal developmental deviations, such as the occurrence of supernumerary cell bodies. Three antibodies that bind either to single types or small sets of different neurons are used to construct complete distribution patterns of antigenically related cells. Three other antibodies are used to create cell body distribution maps of antigenically homologous primary mechanosensory cells responding to noxious or pressure stimulation which form a subset of the cells stained by the antibody. Furthermore, antibodies against the pressure cells helped in the location of two different specific antigens for the same identified nerve cell.
Single cholinergic receptor channel currents in cultured human muscle
Authors: Jackson MB , Lecar H , Askanas V , Engel WK
Published: March 2018

Single cholinergic channel currents were recorded in adult human muscle tissue culture. The agonists suberyldicholine and carbamylcholine produce channels with the same conductance as channels produced by acetylcholine but with different closing kinetics. The antagonist tubocurarine, alone or mixed with suberyldicholine, activates channels which close very rapidly. For agonist-activated channels, the distribution of open state lifetimes shows deviations from the usual single exponential form. An excess of short duration openings indicates the presence of an additional faster kinetic process. The lifetime distribution data can be interpreted in terms of varying proportions of slow and fast components which are present in a ratio determined by curve-fitting the appropriate two-exponential function to observed open time distributions. This ratio shows great variability in muscle from older cultures, but the fast and slow time constants are relatively constant. The observation of double exponential open time distributions indicates that the mechanism of channel closing is more complicated than earlier evidence indicated.
Branching structure of motoneuron stem dendrites: a study of neck muscle motoneurons intracellularly stained with horseradish peroxidase in the cat
Authors: Rose PK
Published: March 2018

The branching structure of the stem dendrites of five motoneurons innervating the dorsal neck muscles, biventer cervicis and complexus, was examined in the adult cat using intracellular staining techniques. The dendritic tree of each motoneuron was reconstructed completely and then dissected into several parts, each corresponding to the branches. Twenty-five of the 49 stem dendrites examined had branches which confined to a small region of the territory occupied by the complete dendritic tree. These dendrites were distributed to one of three zones, a ventral zone deep in the ventral horn, a lateral zone dorsolateral to the motor nucleus, and a medial zone dorsomedial to the motor nucleus. The remaining stem dendrites projected to two or more of these zones and occasionally occupied a region almost as large as the territory occupied by the complete dendritic tree. The frequency of each type of stem dendrite, defined according to the number and location of the zones to which they projected, was remarkably consistent from motoneuron to motoneuron. The maximum order of branching reached by stem dendrites of biventer cervicis and complexus motoneurons was variable. Stem dendrites whose maximum order of branching was four or less usually had one major stalk from which emerged simple, unbranched, side processes. The branching structure was not related, in a simple manner, to the dendritic distribution pattern. These results indicate that the distribution and branching structure of motoneuron stem dendrites are organized in a complex, but precise, fashion which could play an important role in the integrative properties of the motoneuron.
A tonic gamma-aminobutyric acid-mediated inhibition of cholinergic amacrine cells in rabbit retina
Authors: Massey SC , Redburn DA
Published: March 2018

Using the in vivo rabbit eyecup, we have studied the light-evoked release of acetylcholine (ACh) which is presumed to indicate the activity of cholinergic amacrine cells. Gamma-Aminobutyric acid (GABA) inhibited the light-evoked release of ACh (IC50 congruent to 1 mM), but the GABA antagonists bicuculline (5 micro M) and picrotoxin (20 micro M) potentiated the light-evoked release and markedly increased the resting release of ACh. This bicuculline/picrotoxin-evoked release was calcium dependent and the effects of bicuculline, but not picrotoxin, were blocked by muscimol, a potent GABA agonist. Muscimol also inhibited the light-evoked release of ACh (IC50 less than 1 micro M) and was at least 1000 times more potent than GABA. Nipecotic acid (1 mM), a GABA transport blocker, also inhibited the light-evoked release of ACh, but the effect was slow in onset and recovery was prompt. We conclude that the cholinergic amacrine cells of rabbit retina are inhibited by GABA. The relatively weak action of GABA, compared to muscimol, may be due to the presence of avid GABA transport systems. We ascribe the excitatory effects of bicuculline and picrotoxin to the antagonism of endogenous GABA, suggesting that the cholinergic cells are influenced by a tonic release of GABA. This is consistent with the effects of nipecotic acid. Although we are unable to specify the synaptic arrangements involved, we suggest that the most likely interaction is directly between GABA amacrine cells and the cholinergic amacrine cells and/or their presumed bipolar cell inputs.
Organized behavioral responses to lateral hypothalamic electrical stimulation in infant rats
Authors: Moran TH , Schwartz GJ , Blass EM
Published: March 2018

Brief trains of electrical stimulation (500 msec) were administered to 3-, 6-, 10-, and 15-day-old rat pups through electrodes directed at the medical forebrain bundle (MFB) at the level of the lateral hypothalamus. Stimulation was given at three different frequencies: once per 30 sec, once per 20 sec, and once per 10 sec. Pups 10 days of age and younger became behaviorally activated by stimulation and reliably emitted a series of behavioral responses including mouthing, licking, pawing, gaping, probing, and stretch and lordosis responses. Behavior increased with increasing frequency of stimulation and became more organized with age. Sequences of organized behavior patterns are elicited by MFB stimulation which in their culmination take on the characteristics of motivational responses. Fifteen-day-old pups did not respond to these stimulation parameters. These findings indicate that the components of motivational systems are present and can be elicited at an early age. As development progresses, responses become more organized until stimulation parameters effective in rats 3 to 10 days of age become ineffective in activating behavior in day 15 pups.
Pathfinding by neuronal growth cones in grasshopper embryos. II. Selective fasciculation onto specific axonal pathways
Authors: Raper JA , Bastiani M , Goodman CS
Published: March 2018

In the previous paper (Raper, J.A., M. Bastiani, and C.S. Goodman (1983) J. Neurosci. 3:20–30) we showed that the growth cones of two sibling neurons, the G and C cells, follow the same route in the developing grasshopper neuropil until they reach a stereotypic choice point. Here their growth cones diverge from each other as G turns and extends anteriorly and C turns and extends posteriorly. In this paper we show that the G and C growth cones fasciculate and extend in opposite directions upon a specific bundle of four axons. This occurs even though many other axons are within filopodial reach of the G and C growth cones. We identified the four neurons (the A1, A2, P1, and P2 cells) whose axons form the bundle that G and C extend upon by filling individual axons with Lucifer Yellow and viewing the filled cells in living embryos and by filling individual neurons with HRP and reconstructing the axon bundle from electron micrographs. The G neuron extends anteriorly in the bundle containing these four axons; the C neuron extends posteriorly in the same bundle only after several other axons have joined in. These results suggest that the growth cones of the G and C neurons are determined to recognize and extend upon labeled axons, leading us to propose the “labeled pathways” hypothesis.
Regional distribution of calcium- and cyclic adenosine 3':5'- monophosphate-regulated protein phosphorylation systems in mammalian brain. I. Particulate systems
Authors: Walaas SI , Nairn AC , Greengard P
Published: March 2018

The regional distribution of phosphoproteins whose phosphorylation is regulated either by cyclic AMP or by calcium in combination with calmodulin or phospholipid has been investigated in particulate preparations from rat CNS. About 30 distinct phosphoproteins were observed. These phosphoproteins exhibited widely different patterns of regional distribution. Based upon distribution patterns, we have divided these phosphoproteins into three categories: category A, phosphoproteins found in all parts of the CNS in approximately equal amounts; category B, phosphoproteins which are widely distributed within the CNS but show large regional variations; and category C, phosphoproteins which show a highly restricted regional distribution. We have tentatively interpreted the results on particulate phosphoproteins in the following way: some are present in all or nearly all brain cells, others are present only in certain classes of brain cells, and still others have an even more limited distribution, being present in only a single type of brain cell. The regional distribution of particulate protein kinase activity was also examined. Calcium/calmodulin-dependent protein kinase activity had a marked regional distribution, whereas cyclic AMP-dependent protein kinase activity was more evenly distributed. Calcium/phospholipid-dependent protein kinase activity was barely detectable under the experimental conditions used. This investigation thus demonstrates striking differences in the regional distribution of particulate protein phosphorylation systems in mammalian brain. These regional differences may reflect highly specific functional roles for certain of these protein phosphorylation systems. Similar conclusions concerning cytosolic protein phosphorylation systems are described in the accompanying paper.
Glutamate decarboxylase immunoreactivity and gamma-[3H] aminobutyric acid accumulation within the same neurons in dissociated cell cultures of cerebral cortex
Authors: Neale EA , Oertel WH , Bowers LM , Weise VK
Published: March 2018

In order to evaluate the reliability of high affinity [3H]GABA accumulation as a marker for GABAergic neurons, murine cerebral cortical neurons were studied in dissociated cell culture. Cultures which had been incubated in [3H]GABA were stained immunohistochemically for the GABA-synthesizing enzyme, glutamate decarboxylase, fixed with paraformaldehyde, and subsequently processed for radioautography. In mature cultures, there was an 84 to 94% correlation between the presence of the enzyme and [3H]GABA uptake within the same cortical neurons. These data provide direct evidence that those neurons which synthesize GABA are the same neurons which are labeled by high affinity [3H]GABA uptake.
The plastic response to monocular deprivation persists in kitten visual cortex after chronic depletion of norepinephrine
Authors: Bear MF , Daniels JD
Published: March 2018

In order to clarify the role of norepinephrine (NE) in visual cortical plasticity, we monocularly deprived kittens that had received systemic injections of the neurotoxin 6-hydroxydopamine (6-OHDA) shortly after birth. We found, using high pressure liquid chromatography, that this means of drug treatment produces a permanent and substantial reduction in the level of cortical NE as compared with littermate controls. Nonetheless, single unit recording in area 17 of these kittens revealed no difference in the cortical response to monocular deprivation: both drug-treated and control kittens displayed large ocular dominance shifts to the open eye. Because local depletion of NE by intracortical 6-OHDA in kittens can prevent the expected ocular dominance shift after short-term monocular deprivation, we propose that neocortex has the capacity to compensate for chronic depletion of NE in a way which allows for the possibility of plastic changes.
Selective labeling of spiral ganglion and granule cells with D- aspartate in the auditory system of cat and guinea pig
Authors: Oliver DL , Potashner SJ , Jones DR , Morest DK
Published: March 2018

The present study sought to locate putative glutamatergic or aspartatergic pathways in the auditory system of cats and guinea pigs. We injected 0.06 to 3 mM D-[3H] aspartate (D-Asp) in the cochlear nucleus before preparation for light microscopic autoradiography. At short survival times (15 and 40 min) there was heavy labeling of astrocytic somata. Labeling patterns typical of cochlear nerve endings decorated neurons in the cochlear nucleus, e.g., cell bodies and dendritic trunks of octopus cells. Labeling patterns consistent with retrograde axonal transport by the parallel fibers of granule cells appeared in the molecular layer of the dorsal cochlear nucleus and in the external granular layer. Retrograde labeling of the cochlear nerve root fibers also occurred. Consistent with these results are companion biochemical findings on the rapidly dissected cochlear nuclei of guinea pigs. The dorsal, anteroventral, and posteroventral cochlear nuclei, each, evinced uptake of D-Asp. Subsequently, electrical stimulation of each nucleus released a portion of the accumulated amino acid. Most of this release probably came from synaptic endings. Another group of experiments compared autoradiographic localization of 0.06 to 3 mM D- Asp to that of horseradish peroxidase (HRP) 6 hr to 2 d after injections in the cochlear nucleus. Astroglial cell bodies were no longer labeled by D-Asp, but spiral ganglion cell bodies in the cochlea and granule cell bodies in the cochlear nucleus were. Perikarya of the periolivary and ventral cochlear nuclei projecting to the dorsal cochlear nucleus were labeled by HRP and not by D-Asp. Thus, comparisons with the HRP findings indicate that D-Asp labeling resulted from a selective retrograde transport. There was no evidence for a selective anterograde axonal transport. The present observations support the hypothesis that cochlear nerve fibers and granule cells may use L-glutamate and/or L-aspartate as a transmitter in the cochlear nucleus.
Ca++/calmodulin-regulated protein phosphorylation in the Aplysia nervous system
Authors: Novak-Hofer I , Levitan IB
Published: March 2018

Protein substrates for an endogenous CA++/calmodulin-dependent protein kinase were characterized in the Aplysia nervous system. Ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-washed membrane fractions from Aplysia ganglia contain an endogenous Ca++/calmodulin-dependent protein kinase which phosphorylates a number of membrane proteins. Such washed membrane preparations exhibit little or no adenosine 3′:5′-cyclic phosphate (cAMP)-dependent protein kinase activity but do contain substrates for exogenously added catalytic subunit of cAMP-dependent protein kinase. Low concentrations of catalytic subunit rapidly stimulate the phosphorylation of a protein of Mr 70,000 and of a 52,000-dalton doublet, indicating that these proteins are major substrates for this enzyme. Phosphopeptide patterns obtained after limited proteolysis suggest that the 70,000-dalton protein and the 52,000-dalton doublet are similar in structure and that their phosphorylation is stimulated both by Ca++/calmodulin and by catalytic subunit. The 52,000-dalton doublet consists of two closely spaced bands: the phosphorylation of the upper band is stimulated by catalytic subunit, whereas the phosphorylation of the lower band is stimulated by the endogenous Ca++/calmodulin-dependent protein kinase. The results suggest that in Aplysia membranes a number of proteins can be phosphorylated by both Ca++/calmodulin-dependent protein kinase and catalytic subunit of cAMP-dependent protein kinase. This convergence of biochemical effects of Ca++ and cAMP may play a role in some of their physiological actions in molluscan neurons.
Coupling among identified cells in mammalian nervous system cultures
Authors: Kettenmann H , Orkand RK , Schachner M
Published: March 2018

Cell coupling can be demonstrated among groups of oligodendrocytes, astrocytes, and fibroblasts or fibroblast-like cells, but not for dorsal root ganglion neurons, Schwann cells, or macrophages in mouse or rat cell cultures. Neurons were identified by their ability to generate action potentials. Non-neuronal cells were recognized immunologically by their ability to react with a variety of rhodamine-labeled cell type- specific antibodies. Intracellular injection of the gap junction permeable fluorescent dye Lucifer Yellow and ionic current were used to establish the presence of coupling among these identified cells. Coupling under the culture conditions used in this study does not represent a random membrane interaction between closely apposed cells but rather a form of communication among restricted populations.