bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulus generalization in the tactile system of octopus
Authors: Wells M. J. , Young J. Z.
Published: January 2005

After training octopuses to discriminate between spheres with markedly different numbers of grooves, unrewarded transfer tests with spheres other than those used in training showed a greater number of takes of the previously positive sphere than any other, the previously negative sphere being taken least. However, when the spheres used for training were nearly similar the maximum tendency to take in transfer tests was displaced from the sphere used in positive training in a direction away from the negative one. Conversely, the minimum showed a post‐discrimination gradient in a direction away from the positive. These gradients must be due either to some form of interaction between systems that classify for different degrees of roughness or to the fact that the systems are imperfectly tuned so that each is influenced by a range of frequencies. In either case it is likely that the center contains a linear array of units responding to specific patterns of nerve impulses. This center must lie in the posterior buccal lobe and may be subdivided into eight subsets for the individual arms.

The transfer tests showed that octopuses can detect fine differences in numbers of grooves. A sphere of 3 cm diameter with 6 grooves (10% of surface cut away) was treated differently from one with 7 grooves (11.3% cut away).

After removal of the vertical lobes learning was slowed, but the transfer gradients were similar to those in normal animals. This confirms that although these lobes assist in the setting up of representations elsewhere in the brain they do not themselves contain the cells responsible for classifying the stimulus.
Facilitation of cortical cell activity during spreading depression
Authors: Muñoz‐Martínez Emilio J.
Published: January 2005

The steady potential changes which develops together with spreading depression of the cat sensoriomotor cortex were recorded at several cortical depths and related with concomitant modifications in cell firing rates.

In most cases, it was found that the slow negative wave which spreads on the cortical surface does not invade the deep cortical layers. In these cases only a slow positive wave was recorded at the deep layers.

At each layer the cell firing rates modification of PT and non‐identified neurons consisted of an initial acceleration followed by a depression. The deeper the recorded cells, the more prolonged the acceleration and shorter lasting the depression. At layers invaded by the slow negative wave, acceleration occurred during a part or all the temporal course of such wave. At layers not invaded by the slow negative wave, acceleration occurred coinciding with the slow positive wave.

Acceleration of cell firing is believed to result from an adequate “local” active or “remote” passive depolarization of the cortical cells. Depression could result from excessive depolarization of the cortical cells. Depression could result from excessive depolarization of cortical neurons and presynaptic fibers.
Isolated dorsal root ganglion neurons in culture: Cytological maturation and extension of electrically active processes
Authors: Okun Lawrence M.
Published: January 2005

Dissociated chick embryo dorsal root ganglion cells were maintained in vitro for long periods (up to 7 weeks) in cultures essentially free of nonneuronal cells. The cultured neurons attained an advanced stage of cytological maturity and extended long, highly branched processes which formed elaborate networks. Electrical activity was evoked and recorded extracellularly from these processes. Responses obtained from the processes of young (19–20 hr), fully isolated cells indicate that the ability to propagate action potentials is present very early in newly extended fibers and can be developed by neurons deprived of contact with any other cells. Complex responses evoked by single stimulus pulses suggest that many processes, especially in older cultures, contained more than a single active fiber.
Aromatic acid decarboxylase and choline acetylase activities in a single identified 5‐HT containing cell of the leech
Authors: Coggeshall Richard E. , Dewhurst Susan A. , Weinreich Daniel , McCaman Richard E.
Published: January 2005

The two largest cells (Retzius cells) in a typical ganglion of the leech nervous system have been shown previously to contain a high concentration of 5‐hydroxytryptamine (5‐HT). The present study demonstrates that the isolated Retzius cell somata contain approximately 40% of the total aromatic acid decarboxylase activity of a single ganglion. A single Retzius cell has approximately 70 times more enzyme activity than adjacent “control” cells. Since this enzyme activity subserves the synthesis of 5‐HT, a metabolic basis is provided for the cell‐specific accumulation of the amine in the Retzius cells. Further indication of the specificity of the above metabolic relationship was obtained from the study of the distribution of choline acetylase, the enzyme responsible for the synthesis of acetylcholine. The specific activity (enzyme activity per unit of protein) of the acetylase in the “control” cells is nearly 8 times greater than that in the Retzius cell.
Neural mechanisms underlying behavior in the locust Schistocerca gregaria I. Physiology of identified motorneurons in the metathoracic ganglion
Authors: Hoyle Graham , Burrows Malcolm
Published: January 2005

A preparation of the desert locust, Schistocera gregaria, has been developed, in which it was possible to work with identified neurons while still allowing some behavior. A total of 26 motorneurons to the hind leg were studied singly, and in various pairs, both by direct stimulation, and by recording during spontaneous activity and various reflex actions. Motorneurons were identified by passing current into their somata and correlating the evoked somata spikes with extracellularly or intracellularly recorded events in the muscles. Tension of the muscle was also recorded and motor axons were stimulated to evoke antidromic spikes in the somata. Both epsp's and ipsp's can be seen clearly in recordings from the somata; spikes appear as electrotonically conducted remnants only. Somata exhibited little or no electrogenesis. It is inferred that impulses are initiated in a zone tentatively identified with the region of emergence of the motor axon from the neuropil. Integration occurs in the neuropilar segment, with the soma serving as a parallel RC element. Data was obtained on the central mechanisms of coordination of synergistic and antagonistic motorneurons and on the modes of excitation of slow and fast neurons to the same muscles.
Mechanisms involved in spreading depression
Authors: Van Harreveld A. , Fifková Eva
Published: January 2005

Application of unlabelled glutamate to the isolated chicken retina caused an increase in the tissue transparency and a release of labelled glutamate with which the retina had previously been charged. The threshold for both responses was about 0.2 mM. Stimulation with KCI and direct current elicited transparency changes at a threshold of 8 mM and 4–6 V, respectively, and a release of the label at higher KCl concentrations (75 mM) and potentials (15 V). The transparency change caused by glutamate stimulation was severely depressed by MgC12 (10–15 mM) in contrast to the changes elicited by KC1 and direct current which were little affected by Mg ions. It was postulated that glutamate causes transparency changes by acting on neuronal elements. KC1 would act on glia and would only in high concentrations affect neurons. It was furthermore suggested that the propagation of spreading depression is dependent both on the release of glutamate from the intracellular compartment and on the depolarization of neuronal elements resulting from this release.
Some physiological and biochemical features of striated muscles reinnervated by preganglionic sympathetic fibers
Authors: Ramirez Beatriz , Luco J. V.
Published: January 2005

Skeletal muscle fibers can be reinnervated by motor cholinergic fibers, that is, functional connection can be achieved. However, functional connection implies not only the capacity of the nerve impulse to elicit a contractile response but also the capability of the reinnervating neurons to evoke particular modifications of the physiological and biological features of the muscles.

In order to search for some of the modifications due to reinnervation by preganglionic sympathetic fibers, muscle contraction time was studied in three different preparations of adult cats: a) cricothyroid muscle reinnervated by preganglionic fibers; b) cricothyroideus reinnervated by its own nerve; and c) the corresponding normal neuromuscular preparation. The activities of malic dehydrogenase, of aldolase and pyruvic kinase were studied in these three preparations as well as in the denervated cricothyroid muscles.

Reinnervation by preganglionic fibers prolonged the twich contraction time, whereas, self‐reinnervation did not alter it. On the other hand, the activities of the three enzymes decreased as a result of denervation. In contrast, the muscle reinnervated with sympathetic preganglionic fibers partially recovered the normal level of malic dehydrogenase and the aldolase activities; but showed no modification in the level of pyruvic kinase activity. Conversely, in the muscle fibers reinnervated by their own nerve, the activity of the three enzymes returned to normal levels. The shortening of contraction time of the preganglionic reinnervated muscle correlates well with the features of the enzymic activities found in these muscles. It can be concluded: a) preganglionic sympathetic axons are able to achieve functional connections with striated muscles and b) considering the trophic effect, preganglionic fibers resemble the motor nerve supplying slow muscles.
Histofluorescence study of chromaffin cells in dissociated cell cultures of chick embryo sympathetic ganglia
Authors: Jacobowitz David M. , Greene Lloyd A.
Published: January 2005

Chromaffin cells were studied by fluorescence microscopy in long‐term cell cultures of dissociated chick embryo sympathetic ganglia. These cells were distinguishable in culture from the sympathetic ganglionic neurons by their small size, relative infrequency of occurrence, intense fluorescence and survival in the absence of nerve growth factor (NGF). By several weeks in culture, with or without NGF in the medium, the chromaffin cells produced extensive ramifications of fluorescent varicose processes. It is suggested that at least part of the intraganglionic system of adrenergic varicose terminals arises from chromaffin cells. This capability with regard to fiber production lends credence to the suggestion that chromaffin cells may play an active role in ganglionic function.
Optimum topographical conditions for reverberating cortical spreading depression in rats
Authors: Shibata M. , Bureš J.
Published: January 2005

Reverberation of cortical spreading depression (RCSD) around circular cortical lesions was studied in anesthetized rats. Reverberation was started by KCl injection into an area recovering from a first CSD wave in a narrow region between the lesion and the sagittal sulcus. Frontal lesions 3.3 mm in diameter yielded less reliable reverberation than lesions 5.2 mm in diameter. With continuing reverberation the spreading rate of CSD gradually decreased. Reverberation stopped when the CSD relocity dropped below 2.2 mm/min. With large lesions (5.2 mm in diameter) RCSD lasted longer with frontal (12.2 ± 2.0 cycles) than with parietal (4.0 ± 0.4) and occipital (4.4 ± 0.9) obstacles. Application of 10± KCl on the cortical area between the lesion and the sagittal sulcus could also elicit RCSD because the CSD waves spreading in the rostral and caudal directions were not generated simultaneously and some of them went round the obstacle without being intercepted by the opposite wave. The experimental data agree with the mathematical model of excitation spreading in simply connected sheets of excitable tissue and indicate regional differences in CSD susceptibility in the rat.
Localization and identification of the receptors by electron micrographic and ablation studies
Authors: Pigon Andrew , Morita Michio , Best Jay Boyd
Published: January 2005

Asexual reproduction (fissioning) in the planarian Dugesia dorotocephala is socially controlled through a cephalic mechanism; isolation releases fissioning, grouping inhibits it; decapitation releases it even in grouped subjects. Experiments were performed to confirm previous indications that direct contact is involved in the sensing of cohorts; the partial release of fissioning in grouped planarians by introduction of a chemically inert lubricant (0.1% purified agar) into the habitat water further confirms the necessity of intimate contact between the sensors and bodily surfaces of the sensed cohorts. Further experiments, correlating electron microscopic observations with the release of fissioning by various selected surgical ablations, reveal the pertinent sensors to be clumps of neural cilia concentrated in the cephalic margins. Comparable structures occur in the chemoreceptors of catfish, lamprey, and honey bee as well as in the olfactory epithelium of mammals.
Effects of thiamine antagonists on nerve conduction. I. Actions of antimetabolites and fern extract on propagated action potentials
Authors: Goldberg Daniel J. , Cooper Jack R.
Published: January 2005

To assess the hypothesis that thiamine is directly involved in the permeability changes at the sodium channel during nerve conduction, the effects of thiamine antagonists on lobster giant axon resting and action potentials were determined. Thiamine antimetabolites, in millimolar concentrations, reversibly decreased the maximum rate of rise and amplitude of the action potential while increasing its duration. In particular, thiamine tert‐butyl disulfide (TTBD) elicited the formation of pronounced shoulders during repolarization, lengthening the action potential by 2–50 times, depending on dose. Antimetabolites also depolarized the resting membrane, but this change was poorly reversible and may indicate a dual mechanism for antimetabolite action. An extract of the fern, Pteris aquilina, reversibly decreased the maximum rate of rise of the action potential and depolarized the resting potential. It also elevated and prolonged the action potential after‐depolarization, sometimes causing repetitive activity. The strength of these actions was correlated with the antithiamine potency of the extract, and was diminished by addition of thiamine to the extract.
Effects of anisomycin on brain protein synthesis and passive avoidance learning in newborn chicks
Authors: Bull R. , Ferrera E. , Orrego F.
Published: January 2005

The effects of anisomycin (ANM) on newborn chicks have been studied with respect to brain protein synthesis, growth, EEG, toxicity, and several passive avoidance learning tasks. It was found that intracerebral ANM (80 nmol) gave a maximum inhibition of brain protein synthesis of 30%, while a combination of subcutaneous (10 μmol; 53 mg/kg) plus intracerebral (80 nmol; 21 μg) ANM, inhibited by 91% in the first 2 hr and by 75% in the subsequent 2 hr period. Cycloheximide (CXM) also in combined injections at the same doses as ANM, inhibited by 97% in the 4 hr that followed injection. However, all the CXM‐injected chicks were dead by 18 hr, while the lethality of ANM did not differ from that of saline. ANM also did not affect EEG measured at 1, 3, 5, or 24 hr following the subcutaneous plus intracerebral injections, nor did ANM affect body or brain growth curves or brain protein accretion.

In the learning experiments, animals were initially trained to peck at water‐coated metal spheres (type A learning) or at water‐imbibed birdseed (types B and C learning) in less than 1 sec, and were exposed to the same lures treated with the aversant methylanthranilate (MeA) one day later on one occasion (types A and B learning) or exposed twice (type C learning) and tested for learning retention one day later. Learning criterion was set as failure to peck at the lure during the first 20 sec of presentation. If ANM was injected 1 hr prior to MeA exposure, large and highly significant memory deficits were found during the retention test, as compared with saline injected controls. No effect of ANM was seen, however, if it was injected one day after learning, indicating that it did not interfere with retrieval mechanisms. ANM also decreased the external manifestations of fear or displeasure that chicks express during retention testing. Such manifestations have a high correlation with pecking suppression (r = 0.88, P < 0.001).
Effects of denervation and colchicine treatment on the chloride conductance of rat skeletal muscle fibers
Authors: Camerino D. , Bryant S. H.
Published: January 2005

Membrane potentials, cable parameters, and component resting conductances were measured in extensor digitorum longus (EDL) muscle fibers from adult rats in vitro at 24°C, after 15 to 18 days of denervation by nerve section, and at seven to ten days following epineural injection of 100 to 450 μg of colchicine in the peroneal nerve. The denervated muscles were paralyzed throughout the experimental period, whereas the colchicine‐treated preparations showed no clinical paralysis except for the first day or two. The EDL from the untreated side served as a control.

Both the denervated and colchicine‐treated fibers were depolarized, showed signs of fibrillation, had tetrodotoxin‐resistant action potentials, and membrane resistance was increased two‐ to sevenfold. In the denervated fibers, mean chloride conductance GCl dropped from a control value of 3196 to 596 μmhos/cm2 while mean potassium conductance GK showed a tendency to rise from 260 to 332 μmhos/cm2. Colchicine‐treated fibers while showing a similar fall in mean GCl from 2993 to 1066 μmhos/cm2, also showed a significant fall in mean GK from 213 to 116 μmhos/cm2.

It was concluded that factors transported by the microtubular system are important for the maintenance of the high resting GCl of mammalian skeletal muscle fibers.
The identification of two inhibitory cells in each segmental ganglion of the leech and studies on the ionic mechanism of the inhibitory junctional potentials produced by these cells
Authors: Sawada Masashi , Wilkinson Joyce M. , McAdoo David J. , Coggeshall Richard E.
Published: January 2005

The present study identifies a pair of inhibitory cells that are located on each anterolateral margin of a leech segmental ganglion. These cells, which we label as cells 119, are electrically interconnected. These cells give rise to inhibitory junctional potentials (ijp's) in contralateral longitudinal body wall muscle cells. The latencies of the ijp's following spikes in cell 119 are variable. The ijp's are caused by transient increases in premeability to the Cl− ion. Previous studies demonstrated that 5‐HT causes a hyperpolarization of body wall muscle cells by increasing the permeability of muscle membrane to the Cl− ion. Accordingly, 5‐HT was searched for in the 119 cell bodies, but autoradiography, fine structure, and gas chromatography‐mass spectrometry gave no indication that 5‐HT was present in these cells. However, the variable latencies of the ijp's may indicate that there is a neuron interposed between cell 119 and the muscle cells. If this is the case, then the interposed neuron should be analyzed for 5‐HT. Further experiments to locate the terminals of cells 119 and the cell bodies of the presumed interposed neurons are thus desirable.
A central inhibitory action of 5‐hydroxytryptamine in the leech
Authors: Sawada Masashi , Coggeshall Richard E.
Published: January 2005

Previous studies indicated that 5‐HT reduced the number of spontaneous excitatory junctional potentials (ejp's) that occurred in leech body wall muscle cells. The present study confirms these findings and shows that the ejp's arise from impulses in motoneuron L. This study further shows that 5‐HT acts by hyperpolarizing and reducing the membrane resistance of neuron L, thus inhibiting the motoneuron and reducing the frequency of spontaneous ejp's on body wall muscle cells. These effects of 5‐HT are not seen when the ganglion is bathed in a high magnesium solution, a finding that suggests that 5‐HT does not act directly on the membrane of motoneuron L. This study demonstrates that 5‐HT can have a central inhibitory effect on body wall muscle contractions. Previous studies provide evidence that 5‐HT may act as a direct neuromuscular inhibitory transmitter and may also take part in peripheral presynaptic inhibition. Thus, if further studies confirm these suggestions, the well‐known inhibitory effect of 5‐HT on leech body wall muscle is a more complex process than was previously thought.
Permeability of the endplate membrane activated by acetylcholine to some organic cations
Authors: Maeno Takashi , Edwards Charles , Anraku Mitsuo
Published: January 2005

The ability of various organic cations to depolarize the ACh‐activated endplate membrane in the absence of Na ions was examined on frog sartorius muscle by measuring the endplate potential on the muscle surface with the moving electrode technique. The ACh‐activated endplate membrane was very permeable to ammonium and its methyl and hydroxy derivatives, and moderately permeable to guanidine derivatives and Tris (hydroxymethyl) aminomethane. The permeability of alkylol derivatives of ammonium diminished progressively with increase in molecular size. The present results suggested that the endplate ionic channels can be represented by a pore of about 6.4 Å in diameter.
Neurophysiological mechanisms involved in photo‐entrainment of the circadian rhythm from the Aplysia eye
Authors: Eskin Arnold
Published: January 2005

An attempt was made to identify the neurophysiological processes involved in entrainment of the circadian rhythm of spontaneous optic nerve potentials from the Aplysia eye by determining whether pharmacological agents or ion substitutions could block phase shifts produced by single light pulses. Knowing which physiological processes are involved in entrainment should help define the morphological pathway traveled by entrainment information.

A secretory step does not appear to be involved in the flow of entrainment information from the environment to the circadian oscillator. A treatment (HiMg LoCa) capable of inhibiting secretion did not interfere with phase shifting by light. Furthermore, treating eyes with putative transmitters or extracts of eyes did not phase shift the free running rhythm. Also, the phase shifting information is not translated into action potentials before reaching the oscillator since TTX–HiMg LoCa solutions did not block the light‐induced phase shift. The photoreceptor potential does seem to be important for light‐induced phase shifts. A correlation was found between the effects of treatments on the ERG and their effects on the light‐induced phase shift. Solutions which decreased the ERG by 90% or more blocked phase shifting whereas solutions which decreased the ERG by less than 74% had no effect on phase shifting by light.

The results from these studies are consistent with two pathways for the flow of phase shifting information to the circadian oscillator. The circadian oscillator may be associated with receptor cells and the entrainment pathway would include a step involving the photoreceptor potential. Alternatively, the circadian oscillator may be associated with secondary cells and receive entrainment information via the photoreceptor potential and passive spread of current through a gap junction. Higher order cells than second‐order ones are probably not involved in the entrainment pathway.
Spreading depression elicited by thermal effects of ultrasonic irradiation of cerebral cortex in rats
Authors: Ueda M. , Bureš J. , Fischer J.
Published: January 2005

Cortical spreading depression (CSD) was elicited by focused ultrasonic irradiation (800 kHz) of exposed cerebral cortex in anesthetized rats. With the acoustic output of 0.65 W at the probe‐tissue contact (3 mm in diameter), CSD was elicited after 28‐sec irradiation in normothermic rats. Reduction of cortical temperature to 31°C increased the threshold irradiation time to 82 sec on the average. Ten‐ to thirty‐sec heating of cerebral cortex with a thermode elicited CSD when surface temperature exceeded 47°C. Histological examination of the cortical areas exposed to threshold irradiation revealed a central coagulation lesion surrounded by edema. It is concluded that the ultrasonic irradiation elicits CSD by dissipated heat. Differences in threshold duration of irradiation in hypothermic and normothermic rats were used to compute the threshold temperature which had to be exceeded in the critical volume of cortex in order to start CSD.
Excitation of the common inhibitory motor neuron: A possible role in the startle reflex of the cockroach, Periplaneta americana
Authors: Fourtner Charles R. , Drewes Charles D.
Published: January 2005

The responses of the widespread common inhibitory motor neuron (CI) to tactile stimulation of the cercus and the abdomen and electrical stimulation of the cercal nerve and the abdominal connectives are investigated. Tactile stimulation produces high frequency (>500 impulses/s) spike discharge in CI with the onset of CI activity preceding the discharge of the excitatory motor neurons. Electrical stimulation of the connectives demonstrates a monosynaptic connection between at least one intermediate sized fiber (conduction velocity = 3.7 m/s) in the abdominal connective and the ipsilateral CIs in the meso‐ and metathoracic ganglia. Electrical stimulation of the cercal nerve suggests a disynaptic path from cercal nerve to CI. Arguments are presented for a cercal afferent‐to‐CI reflex and the possible functional role of early excitation of CI is discussed.
Physiological characteristics and reflex activation of DUM (octopaminergic) neurons of locust metathoracic ganglion
Authors: Hoyle Graham , Dagan Dani
Published: January 2005

Intracellular recordings were made from single or pairs of somata of the dorsal unpaired median (DUM) neurons of the metathoracic ganglion of the locust Schistocerca gregaria and the grasshopper Romalea microptera, during reflex actions, direct electric excitation and orthodromic and antidromic neural stimulation. Some, possibly all, of these neurons are unique, identifiable individuals in regard to their targets, which are specific peripheral muscles. Their physiological properties and the ways they are activated synaptically are, however, similar. Large, overshooting action potentials, comprising three components, occur. The first component in time is small and represents an excitatory synaptic potential for orthodromic stimulation or an axon spike (AS) for antidromic stimulation, electrotonically conducted into the soma. The second component is larger, being an electrotonically conducted integrating segment spike (ISS). The final component is the soma spike (SS). Neither AS nor ISS have a late positive phase, but there is a large, prolonged one for SS. The latter, combined with rapid accommodation, determine a low maximum firing rate for the neurons.

Most nerves entering the ganglion make excitatory inputs onto each DUM neuron, which is readily driven to spike by electric excitation of either connective. There is a great deal of spontaneous excitatory synaptic input to each DUM neuron and a high proportion of it is common. Although there is no detectable electrical coupling between the cells, there is about 30% synchronous firing, apparently due to the common inputs; independent excitation and inhibition also occur. All sensory modalities tested have inputs to the neurons, which tend to fire constantly at a low rate (1 per 3–4 sec). In reflex actions, DUM neurons tend to fire before motor output occurs. It is suggested that the cells will be found to have many functions serving a general role comparable to that achieved by the release of adrenaline in vertebrates.
In vivo responses of paired giant mechanoreceptor neurons in Aplysia abdominal ganglion
Authors: Cobbs J. S. , Pinsker H. M.
Published: January 2005

Two neurons with cell bodies symmetrically located in the abdominal ganglion and giant axons in the left (L1) and right (R1) pleurovisceral connectives of Aplysia californica were examined in vivo and in vitro. Direct stimulation of R1 and L1 in the intact animal does not elicit any observable behavior, suggesting that they are neither motoneurons nor command neurons. These cells respond in vivo to sudden onset mechanical stimulation of widespread regions of the body. R1 and L1 spikes are initiated in at least three different loci: (1) the peripheral axon in the foot, (2) the neuropil of the pleural and/or pedal ganglion, and (3) the neuropil of the abdominal ganglion. Furthermore, R1 and L1 probably have two different mechanisms for spike initiation: (1) sensory (foot), and (2) synaptic (abominal and/or head ganglia). The different loci for spike initiation account for the bidirectional conduction of R1 and L1 spikes. As sensory (mechanoreceptor) neurons, R1 and L1 have peripheral axons in the ipsilateral posterior pedal nerve, show low threshold responses to stimulation of the ipsilateral posterior foot, they are rapidly adapting their responses do not decrease with repetion, and they are not blocked by high Mg++/low Ca++ solutions. As synaptically‐driven neurons, R1 and L1 have widespread bilateral responsiveness, their responses decrease with repetition and their inputs are blocked with high Mg++/low Ca++ solutions. These neurons integrate sensory and synaptic inputs and conduct bidirectionally, however, their output connections must be specified before their behavioral function can be understood.
Changes in synthesis of specific proteins following axotomy: Detection with two‐dimensional gel electrophoresis
Authors: Hall Michael E. , Wilson David L. , Stone George C.
Published: January 2005

Changes in protein synthesis during development and following axotomy were analyzed by two‐dimensional gel electrophoresis. The two major postganglionic nerves emerging from the superior cervical sympathetic ganglia (SCSG) of adult rats were either cut or crushed unilaterally. At intervals ranging from 1 to 112 days after surgery both SCSG were removed and incubated for 1 hr in the presence of 14C‐leucine. Proteins were extracted and subjected to two‐dimensional electrophoretic separation and autoradiography. With this technique, proteins are separated on the basis of isoelectric point and molecular weight. Also, intact SCSG from 1, 2, 7, and 14 day old rats were labeled and analyzed.

It was found that a minority of the separated proteins exhibited some detectable change in relative rate of synthesis following axotomy. Actin exhibited a slight (< 20%) increase in relative synthesis rate while tubulin did not change significantly. There were small but significant differences in the protein patterns following nerve crush, as opposed to nerve cut. Comparison of protein synthesis patterns from developing rat SCSG with those from intact and from axotomized adult SCSG failed to demonstrate any marked similarity between the developmental and the axotomy patterns.
Two mechanisms for spreading depression in the chicken retina
Authors: van Harreveld A.
Published: January 2005

Two mechanisms have been proposed to explain spreading depression (SD): one based on a release of glutamate (Van Harreveld, 1959), and the other on a release of potassium (Grafstein, 1956) from neuronal elements. Both glutamate and KCl cause transparency changes in the retina, comparable to those occurring in this tissue during SD. The glutamate effect is inhibited by MgCl2 (10 mM), in contrast to the transparency change due to KCl which is not affected by Mg++. Also SD is usually inhibited by MgCl2 which suggests that such SDs are based on a glutamate release. Impairment of the tissue metabolism promotes SDs which are insensitive to MgCl2. The resulting failure of the mechanisms that transport K+ and glutamate which leak out of the intracellular compartment back into the cells and fibers, seems to be involved in the generation of Mg++ insensitive SDs. This may facilitate either K‐based SDs or glutamate‐based SDs since the inhibitory effect of Mg++ is counteracted by an enhanced glutamate concentration. Both proposed mechanisms for SD seem to be possible under special circumstances.
Duplication of a spontaneously active neuron in Aplysia: Electrical coupling and effects of a phosphodiesterase inhibitor
Authors: Treistman Steven N.
Published: January 2005

An abdominal ganglion from an Aplysia californica is described, in which cell R15 has anomalously duplicated. The two cells exhibited a high degree of electrical coupling, assuring functional synchrony of output in the cells, which are characterized by a complex firing pattern. Exposure of this ganglion to the phosphodiesterase inhibitor IBMX caused a more altered firing rhythm in one of the cells, as well as an enhanced inhibitory component associated with the coupling potentials between cells, resulting in a loss of synchrony between the two cells.
The calcium‐dependent neuronal release of serotonin and its antagonism by lithium
Authors: Stefano George B. , Catapane Edward J. , Aiello Edward , Hiripi Laszlo
Published: January 2005

The cilio‐excitatory serotonergic innervation of lateral gill cilia of Mytilus edulis was studied in vivo. Peripheral serotonin release was dependent on the external calcium concentration. Serotonin release was inhibited by autodialyzing calcium from the tissue or by increasing the calcium concentration in the medium, as determined by measuring ciliary activity stroboscopically and by biochemical and radioassays of serotonin. Lithium also inhibited serotonin release when added to the external bathing medium. Concomitantly, altering calcium concentrations altered the degree of inhibition of serotonin release caused by lithium. The study demonstrates that the terminal release of the monoamine serotonin is a calcium‐dependent mechanism. The pharmacological effects of lithium in this system appear to be interrelated with the calcium‐dependent releasing mechanism.
The projections of neurosecretory cells in the brain of the North‐American medicinal leech, Macrobdella decora, using intracellular injection of horseradish peroxidase
Authors: Orchard I. , Webb Rodney A.
Published: January 2005

The projections of four anatomically distinct groups of putative neurosecretory cells found within the supra‐oesophageal ganglion of the leech Macrobdella decora were studied by intracellular injection of horseradish peroxidase. All four groups have their own characteristic branching pattern while sharing the common feature of possessing primary branches that project into the dorsal commissure. Numerous secondary processes extend from these primary branches to terminate within the neural lamella, as well as within the neuropile. Electron microscopy of the regions into which these secondary processes project reveals numerous neurosecretory terminals. The data suggests that the midregion of the dorsal commissure constitues a neurohemal complex. These observations strengthen the argument that the four groups of identified cells are indeed neurosecretory.
Neuronal mechanisms for bilateral coordination of salivary gland activity in Helisoma
Authors: Bahls Fred , Kater Stanley B. , Joyner Ronald W.
Published: January 2005

The salivary neuroeffector system of Helisoma consists of the paired salivary glands and buccal ganglia. Previous work demonstrated that neuronal control was required for coordination of activity in the two salivary glands. This neuronal control is provided by a pair of identified buccal ganglion neurons, 4R and 4L. This study examines the organization of this neuronal control and addresses the questions of monosynaptic vs. polysynaptic pathways as well as the bilateral effects of each neuron 4. Action potentials in neuron 4 elicit one‐for‐one EPSPs in a subpopulation of the salivary cells. These EPSPs can, in some cases, be increased by TEA injection into a neuron 4 and are unaffected by the addition of six‐times normal calcium. These data coupled with the constancy of synaptic transmission, as well as morphological evidence, further indicate the monosynaptic nature of the connection between neurons 4 and salivary secretory cells. Three different mechanisms exist to insure that activity in 4R and 4L result in coordinated activation of the salivary glands: (1) Lucifer Yellow injection and direct intracellular recording and stimulation demonstrate that both 4R and 4L can send axons to and innervate both salivary glands; (2) both 4R and 4L receive virtually identical synaptic input from higher‐order buccal ganglion neurons; and (3) 4R and 4L are electrically coupled. Thus, the system is organized with a high degree of redundancy, and bilateral synchrony of glandular activity is assured by mechanisms at various levels of neuronal organization.
Alteration of neuronal activity in response to cyclic nucleotide agents in Aplysia
Authors: Drake Peter F. , Treistman Steven N.
Published: January 2005

Responsiveness of Aplysia neurons to agents that affect cyclic nucleotide levels was not limited to neurons exhibiting a spontaneous bursting activity pattern. Analyses of the I‐V relationship elicited by triangular current ramps within cells exposed to different agents presumably causing elevated cyclic nucleotide levels showed qualitatively similar alterations. These included an increased slope conductance at more negative potentials, possibly related to anomalous rectification, and the induction of a hysteresis in response to a triangular ramp. The paired metacerebral giant cells showed induction of synchronous bursting when exposed to phosphodiesterase inhibitors, and we examined this phenomenon more closely. classical methods to inactivate a presynaptic source did not eliminate the induction of synchronous bursting. Intracellular injection of a phosphodiesterase inhibitor into a metacerebral giant cell caused changes in the current‐voltage relationship similar to those described above for other cells. Subsequent perfusion with the inhibitor caused an enhancement of these effects and the induction of bursting. The alternation of the current‐voltage plot in the metacerebral cells and abdominal ganglion cells is qualitatively similar to that induced in the similarly treated bursting neuron R15, suggesting a similar mechanism of action in both burster and nonburster neurons. The implications of these results for cyclic nucleotide mediation of neuronal events are discussed.
Calcium independence of slow currents underlying spike frequency adaptation
Authors: Donald Partridge L.
Published: January 2005

This study assessed the role of calcium in the activation of the slow potassium current responsible for spike frequency adaptation in molluscan neurons. Inward calcium currents were eliminated by using Co2+, Cd2+, or OCa2+ EGTA in the bathing solution. In each case adaptation was found to persist, as did the slow current believed to be responsible for adaptation. Injection of EGTA into neurons was also found not to block adaptation. This potassium current provides an example of a slow voltage‐dependent potassium process which is independent of calcium influx.
A peptide action in a lobster neuromuscular preparation
Authors: Schwarz Thomas L. , Harris‐Warrick Ronald M. , Glusman Silvio , Kravitz Edward A.
Published: January 2005

The neuropeptide proctolin causes a sustained contraction of the opener muscle of the dactyl of the lobster walking leg. This substance acts directly on the muscle at concentrations as low as 10−10M. The contraction is dependent on extracellular calcium. Neither a significant depolarization nor a detectable change in the input resistance accompanies the response. No presynaptic action of proctolin is indicated; excitatory and inhibitory junctional potential sizes and the frequency of spontaneous miniature excitatory junctional potentials are unaffected.
Dipteran flight motor pattern: Invariabilities and changes during postlarval development
Authors: Kutsch W. , Hug W.
Published: January 2005

For Calliphora the wingbeat frequency and the underlying motoneuronal activity were recorded during adult life. Wingbeat frequency increases during the ten days following last molt. The activity of motoneurons serving four selected flight muscles (nonfibrillar and fibrillar ones) also increases with age. The motoneuronal activity of young and old flies was analyzed statistically (serial and cross‐correlograms, latency and phase histograms). In addition, several wing manipulations were carried out to evaluate the significance of sensory feedback on pattern generation during maturation. These ontogenetic studies suggest a centrally generated motor pattern that (1) is essentially complete with the molt to adulthood, (2) shows a progressive increase in intrinsic activity, and (3) is modulated by sensory feedback from the wing region by the same amount irrespective of age. Similarities in the postlarval development of the flight pattern of neurogenic and myogenic flyers are discussed.
Age‐dependent anatomical changes in an identified neuron in the cns of Aplysia californica
Authors: Papka R. , Peretz B. , Tudor J. , Becker J.
Published: January 2005

Neurons of Aplysia californica are naturally pigmented and the pigment accumulates with age. In the present study the pigment was examined in the same neuron from Aplysia of three postmetamorphic ages: young, sexually mature, and old. The large central neuron, R2, was examined by light and electron microscopy to determine if the pigment possessed properties similar to lipofuscin pigment seen in aging mammalian neurons. We used the same microscopic techniques that demonstrate the presence of lipofuscin in mammalian neurons. Light microscopic studies demonstrated a regional correlation between autofluorescence, staining with Sudan Black, and the naturally occurring pigment in old R2s. Electron microscopic studies revealed the presence of large vacuolated and lamellated membrane‐bound bodies in the peripheral cytoplasm of old R2s, similar to those found in mammalian neurons. The bodies were located in the same region in which autofluorescence and Sudan Black staining were observed. Although the naturally occurring pigment accumulates with age, it acquires characteristics of lipofuscin pigment in the neurons of older sexually mature animals. The presence of these pigment characteristics can be used as an index of aging in Aplysia neurons as they are in mammalian neurons.
Age‐dependent behavioral changes and physiological changes in identified neurons in Aplysia californica
Authors: Rattan Kuldip S. , Peretz Bertram
Published: January 2005

The gill withdrawal reflex (GWR) to direct gill stimulation was studied in sexually mature Aplysia and in those older by at least two months. The GWR threshold in old Aplysia was five‐ to sevenfold higher than that in mature animals. In the habituation paradigm, the GWR amplitude decremented rapidly to zero in old animals whereas in mature animals it persisted for at least ten trials. The GWR could not be dishabituated in old animals. The GWR is an age‐dependent behavior in that parieto‐visceral ganglion suppression of the GWR appears to increase with age. Also the electrophysiological properties of two neurons in the parieto‐visceral ganglion were compared in the two age groups: L7 a neuron which dishabituates the GWR in mature and not in old animals; and R2 which manifests cytological changes with age. In old animals L7′s input resistance was lower, the time constant was increased, and the size of the psp evoked by gill stimulation was smaller than those of mature L7s. Similar membrane changes with age were measured in R2. Soma size of L7 was approximately the same in the two age groups as was that of R2. The physiological parameters of neurons of known function continue to change during postmetamorphic life of Aplysia.
Effect of fatty acids on the membrane fluidity of cultured chick dorsal root ganglion measured by fluorescence photobleaching recovery
Authors: Takenaka Toshifumi , Horie Hidenori , Kawasaki Yukishige
Published: January 2005

The effect of fatty acids on the membrane fluidity in tissue cultured chick embryo dorsal root ganglion was studied by fluorescence recovery method. Lateral motion of the lipid was measured by observing the fluorescent probe, 5‐(octadecylthiocarbamoylamino) fluorescence, F18. The effective lateral diffusion coefficient of the membrane was around 0.30 × 10−8 cm2/sec in control cells, 0.42 × 10−8 cm2/sec in 2‐decenoic acid treated cells, and 0.35 × 10−8 cm2/sec in valeric acid treated cells. From these results it is concluded that effective mobilities of the membrane complex increased about 40% by the external application of 2‐decenoic acid, while valeric acid increased it only 12%. From the physiological results that 2‐decenoic acid inhibits the Na‐channel, it is suggested that this increase in the membrane fluidity might affect the Na‐channel.
Subcellular localization of neutral red staining in Limulus ventral photoreceptors
Authors: Chamberlain Steven C. , Battelle Barbara‐A. , Calman Bruce G.
Published: January 2005

Limulus ventral photoreceptors are vitally stained by neutral red. In other systems such staining has been correlated with the presence of monoamines or neuropeptides. The stained cellular components in ventral photoreceptors are clusters of small ovoids which have been identified as residual bodies. These structures are unlikely candidates for monoamine or neuropeptide synthesis or storage sites, but may be part of the cyclic synthesis and degradation of photosensitive membrane. While vital staining with neutral red is a particularly useful method for identifying certain classes of neurons in vivo, in the case of ventral photoreceptors, the association of the vital staining property with the presence of a particular class of neurotransmitter candidates has proven difficult. Neutral red is useful, however, for visualizing the segmentation of ventral photoreceptors in vivo.
Localization of calcium in nerve fibers
Authors: Chan S. Y. , Ochs S. , Jersild R. A.
Published: January 2005

Using the desheathed nerve preparation, a pyroantimonate precipitation method was used to examine the distribution of electron‐dense particles seen in various organelles of the nerve fibers following exposure of nerve to various levels of Ca2+ in vitro. The presence of Ca2+ in the electron‐dense particles was indicated by their extraction with EGTA and by the use of energy‐dispersive X‐ray microanalysis.

In normal Ringer or in a Ca2+‐free medium, electron‐dense particles were seen associated with the outer membrane of the mitochondria, with the smooth endoplasmic reticulum (SER), along the axolemma and yet others scattered throughout the axoplasm.

When nerves were incubated in media containing higher than normal concentrations of 20–60 mM Ca2+, an increase in the number of such electron‐dense particles was seen in the axoplasm and within the mitochondrial matrix. Nerves loaded with a high concentration of 60mM Ca2+ could be depleted of these particles after transfer to a Ca2+‐free or low Ca2+ Ringer medium.

The sequenstration of Ca2+ in axonal organelles is discussed with respect to Ca2+‐regulatory mechanisms in the axon needed to maintain a low level of Ca2+ which is optimal for the support of axoplasmic transport.