bluuebunny/crossref_metadata_2025 huggingface dataset:
γ‐Aminobutyric acid receptors in brain postsynaptic densities
Authors: Matus Andrew , Pehling Gundula , Wilkinson Diane
Published: January 2005

Rat brain synaptic plasma membranes contain two receptorlike binding sites for the inhibitory transmitter γ‐aminobutyric acid. Postsynaptic junctional structures (postsynaptic densities) isolated from these membranes contain only the higher affinity site enriched more than sixfold compared to the membranes. The results provide the first direct evidence for the association of transmitter receptors with postsynaptic junctional sites in the brain.
Neurite growth promoting factors of embryonic chick—ontogeny, regional distribution, and characteristics
Authors: Riopelle R. J. , Cameron D. A.
Published: January 2005

A single neuronal cell biological assay for NGF has been used to quantitate factors in soluble extract of chick embryo that promote neurite outgrowth. The neurite growth promoting activity is detected as early as day 1.5 of embryonic life. Specific activity increases to maximum over the first four days and then decreases from day 5 to 6 during a growth spurt of the embryo. The tissue distribution of neurite growth promoting activity at eight embryonic days shows higher specific activity in peripheral structures that are richly innervated. Extract from all embryonic stages and from all tissues studied induces neurite outgrowth that is inhibited only partially by antibody to mouse NGF. Furthermore, the kinetics of neurite outgrowth and the neuronal populations responsive to extract differ from that of NGF. These observations indicate heterogeneity of the neurite growth promoting factors in soluble extracts of embryonic chick and demonstrate the presence of these factors before the responsive neurons leave the cell cycle and begin their differentiation processes.
Cerebral [K+]e increase as an index of the differential susceptibility of brain structures to terminal anoxia and electroconvulsive shock
Authors: Bureš J. , Burešová O.
Published: January 2005

The time course of the [K+]e increase elicited by terminal anoxia or by electroconvulsive shock (ECS) was compared in various parts of the rat brain. The [K+]e was measured with ion‐selective microelectrodes stereotaxically introduced into the target area. Respiration arrest induced in anesthetized rats a slow [K+]e increase to about 6–10 mM followed by an abrupt rise to 30–50 mM (doubling time 5–14 sec) in the neocortex, hippocampus, amygdala, caudate nucleus, and thalamus. In the reticular formation, zona incerta, and lateral hypothalamus the second phase of [K+]e increase was much slower (doubling time 30–50 sec) and lacked the autoregenerative character. Trans‐pinnate ECS (50 Hz, 0.5 sec, 80 mA), administered to rats immobilized with gallamine triethiodide, elicited a generalized [K+]e increase of the spreading depression type in neocortex and hippocampus (40 mM) as well as in the caudate nucleus and thalamus (20–30 mM), followed by slow [K+]e decrease (half‐time 40–60 sec). Much lower ECS‐induced [K+]e increase (to 5–6 mM) was observed in the reticular formation, zona incerta, lateral hypothalamus and, surprisingly, in the amygdala. It is concluded that the autoregenerative [K+]e release of spreading depression type develops in structures with high density of membranes reacting to partial depolarization by increased sodium permeability.
Deutocerebrum of the cockroach Blaberus craniifer burm. Quantitative study and automated identification of the glomeruli
Authors: Rospars Jean Pierre , Chambille Irène
Published: January 2005

The glomerular organization of the hemideutocerebrum is analyzed quantitatively, using only spatial position, in four individuals (eight hDTCs) after a visual identification of glomeruli on graphic reconstructions. In order to assess directly the invariance of the neuropil in an insect brain the following is done: (1) The position of each glomerulus is compared to the position A′ it should occupy if the hDTCs were identical. It is shown that in 80 and 71% of the cases, respectively, intra‐ and interindividual comparisons in the studied glomerulus is the nearest to A′. (2) The actual position is equally compared to the theoretical location A″ each glomerulus should occupy if its absolute position could be changed but not its relative position with respect to its neighbors. The calculation of A″ is based on process (3). In 86 and 80% of the cases, respectively, it is found that the actual position is that which is nearest to A″. (3) An automated identification process, based on absolute and relative locations, but completely independent of visual identification, is described. It allows the identification of 77 and 74% of glomeruli, respectively. These matchings are in 96 and 90% of the cases identical to the visual matchings. The location predictability of most glomeruli is discussed to show the existence, nature, and limits of the hemideutocerebral invariance.
Soma spike of neuroendocrine bag cells of aplysia californica
Authors: Acosta‐Urquidi Juan , Dudek F. Edward
Published: January 2005

Soma action potentials of the neuroendocrine bag cells of Aplysia californica were studied with intracellular recording and current injection. Spikes in artificial sea water (ASW) were either graded with increasing depolarizing current pulses, or had a well‐defined threshold. The latter spikes typically had faster rise times with larger overshoots and hyperpolarizing afterpotentials. Repetitive stimulation led to spike potentiation (SP), manifested as an increase in overshoot amplitude and duration of successive spikes in a train. SP was usually detectable at 0.5 Hz, and maximal between 0.8 and 4 Hz. Concomitant accommodation occurred rapidly at ≥5 Hz. The increase in spike duration during SP resulted from a progressive enhancement of an inflection on the repolarizing phase. The inflection was dependent on membrane potential; small depolarizations (5–10 m V) enhanced it; hyperpolarization (<35 m V) reduced it. Solutions with O—Na+ (Tris‐substituted) or O—Ca2+ (1 μM EGTA) revealed mixed Na+/Ca2+ spikes with variable degrees of Na+ versus Ca2+ dominance. Cd2+, Co2+, and Mn2+ reversibly abolished the inflection on the repolarizing phase, indicating that it is Ca2+ mediated; the spike was reduced irreversibly at higher concentrations. SP was generally reduced only if the spike was severely attenuated. It is proposed that SP results primarily from a voltage‐ and time‐dependent potassium inactivation which then unmasks a calcium current. SP may play a role in augmenting the release of egg‐laying hormone.
Multiple‐rate components of axonally transported proteins in the hypothalamo‐neurohypophysial system of the rat
Authors: Fink David J. , Russell James T. , Gainer Harold , Brownstein Michael J. , Baumgold Jesse
Published: January 2005

The transport of labeled proteins from the hypothalamus to the neurohypophysis following 35 S‐methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short‐axon systems. Multiple‐rate components comparable to those found in other neuronal systems were demonstrated. Neurosecretory vesicle‐containing proteins (e.g., neurophysins) were transported at fast rates (≥ 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two‐dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in this system.
Some effects of proctolin on the cardiac ganglion of the maine lobster, Homarus americanus (Milne Edwards)
Authors: Miller Mark W. , Sullivan Robert E.
Published: January 2005

The neuropeptide proctolin has excitatory effects on the isolated lobster cardiac ganglion. Selective application to the anterior cell body region produces a dose‐dependent (10−8–10−5M) prolonged depolarization of large anterior cells as well as marked increases in burst frequency and/or duration. In ganglia which have been silenced with tetrodotoxin, proctolin application to anterior cells elicits long‐lasting depolarizing responses which are accompained by a 10–30% increase of the apparent membrane input resistance. Higher proctolin concentrations produce high‐frequency trains of driver potentials. It is proposed that a proctolinlike peptide may serve a neurohumoral role in the lobster cardiac ganglion and that the anterior motor neurons exhibit endogenous rhythmicity in its presence.
Amine modulation of the neurogenic Limulus heart
Authors: Augustine George J. , Fetterer Raymond , Watson Winsor H.
Published: January 2005

(1) The biogenic amines octopamine (OCT), dopamine (DA), epinephrine (E), and norepinephrine (NE) cause dose‐dependent increases in both the rate and amplitude of contractions of the isolated Limulus heart‐cardiac ganglion. Their relative ability to produce this excitation is OCT > DA ∼ E > NE. (2) The excitatory effects of all these amines are antagonized by the α‐adrenergic blocker phentolamine and the dopaminergic antagonist haloperidol. The β‐adrenergic antagonist dichloroisoproterenol slightly reduces amine excitation, but is also a partial agonist. The β‐adrenergic antagonist propanolol, the α‐blocker phenoxybenzamine, and the serotonin antagonist metergoline are ineffective. (3) In addition to their excitatory effects, DA and, to a lesser extent, NE initially reduce contraction rate and amplitude. (4) The transient inhibition is eliminated selectively by metergoline and is unaffected by the other antagonists. (5) The amines all increase the frequency of cardiac ganglion electrical bursting activity, whether ganglia are isolated or attached to cardiac muscle. Dopamine and NE also transiently inhibit the cardiac ganglion. (6) The amines do not alter myocardial resting tension, contractility, or membrane potential. (7) These amines appear to exert their modulatory effects on Limulus heart by altering the properties of the neurons which comprise its cardiac ganglion.
Formation of novel central and peripheral connections between molluscan central neurons in organ cultured ganglia
Authors: Hadley Robert D. , Wong Richard G. , Kater Stanley B. , Barker David L. , Bulloch Andrew G. M.
Published: January 2005

An in vitro organ culture system for buccal ganglia of the adult snail, Helisoma, is described. The system supports: (1) maintenance of characterstic electrophysiological parameters of identified neurons over seven days of culture; (2) choline metabolism including uptake and synthesis over the same duration; (3) sprouting and growth of neurons in response to axotomy; (4) the formation of novel central electrotonic connections between identified neurons as a result of sprouting and growth. These observations on neuronal growth and the formation of connections are similar to those made with in vivo culture. The use of in vitro culture allows precise manipulations not previously possible. When buccal ganglia are cultured in vitro with the cut distal ends of peripheral nerve trunks held closely apposed, axons of neurons 5R and 5L in the nerve trunks are capable of forming electrotonic connections similar to central connections. The capability of these neurons to form electrotonic connections via their peripheral axons implies that special structures (i. e., central neurites) are not required for the formation of connections; and neither are special environments (i. e., the central neurites) required for these connections.
Differential effects of amino acids on the period of the circadian rhythm from the Aplysia eye
Authors: Eskin Arnold
Published: January 2005

The effect of continuous treatments of single L‐amino acids (0.1mM) on the free running rhythm from the isolated Aplysia eye was examined. A variation in the change in free running period produced by different amino acids was observed. Two well‐known precursors of neurotransmitter (tyrosine, tryptophan) had the largest effects. These amino acids lengthened the period ca. 1.7 h. Another group of amino acids (alanine, threonine, proline) lengthened the period by about 1 h. Smaller effects were produced by aspartic acid and leucine and no effects were caused by lysine, glycine, valine, and serine. Phenylalanine may shorten the period a small amount. Glucose (5mM) lengthens the period a small amount (0.4 h), decreases the effect of tyrosine somewhat, and has no effect on the lengthening of the period produced by tryptophan. Three amino acids not involved in protein synthesis (ornithine, β‐alanine, citrulline) had at most small effects on the free running period. Also, D‐tryptophan lengthened the period by 0.6 h but the effect of D‐tryptophan was considerably smaller than the effect of L‐tryptophan. A few of the amino acids had small short‐term effects on spike rate and longer‐term effects on the amplitudes of the rhythms but these effects did not correlate with the effects of the amino acids on the free running period. Though continuous treatments of certain amino acids lengthened the periods, shorter treatments (tryptophan, 6 h) did not phase‐shift the rhythm. Since eyes maintained in a commonly used culture medium have longer periods than eyes in a simple seawater medium, the amino acids of the culture medium must be responsible, at least in part, for the lengthening effect of the culture medium. The mechanism of action of the amino acids is unknown. The magnitude of the effects did not correlate with physical‐chemical properties of the amino acids nor with whether the amino acids were “essential” or “nonessential.” The effects of the amino acids may be mediated by their effects on neurotransmitter and/or protein synthesis.
Ventriculo–cisternal perfusion of twelve amino acids in the rabbit
Authors: Davson H. , Hollingsworth J. G. , Carey M. B. , Fenstermacher J. D.
Published: January 2005

The clearances of twelve amino acids from the ventricles during ventriculocisternal perfusion in the rabbit have been measured; uptake by the brain was also measured and this permitted the separate computation of loss to brain and loss to blood during the perfusion. Clearance under carrier‐free conditions was greater than when a concentration of 5mM unlabeled amino acid was present in the perfusion fluid. Brain uptake was also usually reduced by the presence of unlabeled amino acid due presumably to suppression of accumulation by brain cells. Reduction of transport across the blood‐brain barrier would tend to increase brain uptake, and there was some evidence for a balance between the two opposing tendencies. Inhibition of clearance of a given labeled amino acid could be brought about by unlabeled amino acids of different molecular species. In general, the amino acids fell into three categories: neutral, acidic, and basic, and there was some overlap between them; of the neutral amino acids the A‐ and L‐classification of Christensen was valid, although once again there was some overlap. If, during ventriculo‐cisternal perfusion of a labeled amino acid, the activity of this labeled amino acid in the blood was raised well above that in the inflowing perfusion fluid, the labeled amino acid continued to be cleared from the perfusion fluid, suggesting uphill transport. On this basis it was suggested that the normally low concentrations of amino acids in the cerebrospinal fluid (CSF), by comparison with those in plasma, were due to an active transport from the CSF to the blood. Substrate‐facilitated transport, whereby the penetration of labeled amino acid into the perfusion fluid from blood could be accelerated by adding unlabeled amino acid to the perfusion fluid, or vice versa, was demonstrated.
Cobalt mapping of the nervous system: How to avoid artifacts
Authors: Hackney C. M. , Altman J. S.
Published: January 2005

Infusion of cobalt ions into cut axons is an established method for tracing neuron projections in the central nervous system. Artifacts, where unintended neurons are stained, however, have been reported, leading to difficulties in interpretation. Experiments in the locust Schistocera gregaria Forskål show that such artifacts can be induced through damage to axons caused by cutting peripheral nerves and by using high cobalt chloride concentrations (0.4M and above). Mixtures of cobalt and nickel chlorides and nickel chloride alone were introduced into different branches of the same nerve and developed with rubeanic acid to give precipitates of different colors in the two sets of axons. Preparations were examined with the light microscope, where mixing of ions would appear as intermediate colors, and by x‐ray probe microanalysis. No evidence for leakage of metal ions from the filled axons or for ion uptake by other axons could be detected, provided that low concentrations of cobalt and nickel chlorides were used and nerve cutting was reduced to a minimum by making preparations in vivo. If extreme conditions are avoided when making the preparation, the risk of producing artifacts is minimized, thus enabling the cobalt method to be used with greater confidence for describing neuronal projections.
Neuronal elements in snail tentacles as revealed by horseradish peroxidase backfilling
Authors: Chase Ronald , Kamil Rifa'at
Published: January 2005

The snail tentacle ganglion is a prominent structure that innervates an epithelial pad sensitive to wind and odors. Its neural composition, and that of the sensory pad, was studied in the terrestrial snail Achatina fulica by applying horseradish peroxidase to the distal end of the cut tentactle nerve. Five types of neurons were labelled by the procedure: receptors, located in the subepithelial region; three kinds of interneurons, located in the ganglion and its digitlike extensions; and a bipolar neuron, located in the dermo‐muscular wall of the tentacle. In contrast to earlier descriptions based on silver stains, the present results demonstrate the presence of neurons of large size (soma diameters up to 46 μm). Also, contrary to earlier interpretations, the results indicate that all five identified cell types send axons directly to the CNS.
Modulation of the Aplysia gill withdrawal reflex by dopamine
Authors: Ruben Peter , Lukowiak Ken
Published: January 2005

The ability of dopamine to modulate gill contractions was tested in Aplysia. When dopamine was perfused through the gill vasculature, gill contractions caused by siphon stimulation (gill withdrawal reflex) and by depolarization of the gill motor neuron L7 were increased in amplitude, as compared with those evoked during seawater perfusion. Habituation of gill movements, brought about by repetitive stimulation of the siphon or of L7, was prevented by dopamine. Despite the absence of reflex habituation, the number of action potentials in central gill motor neurons, evoked by siphon stimulation, showed normal decrement. Dopamine's effects were blocked when the ctenidial nerve was cut or when L7 hyperpolarized. These data suggest that dopamine acts peripherally to increase the efficacy of L7's synpatic transmission onto gill muscle or elements of the gill neural plexus.
Aminergic neurons in the anterior nervous system of the rat acanthocephalan moniliformis dubius
Authors: Eva Budziakowski M. , Mettrick D. F. , Webb Rodney A.
Published: January 2005

The cerebral ganglion and nerve tracts of Moniliformis dubius show intense, specific, green fluorescence that is also associated with the lateral and apical sensory bulbs. Radioenzymatic assays showed that high levels of dopamine were present but only small amounts of the catecholamines norepinephrine and epinephrine were identified. Incubations of the proboscis sac in dilute solutions of dopamine increased fluorescence while incubations in reserpine resulted in loss of fluorescence. Nonfluorogenic amine octopamine was also detected radioenzymatically. Neutral red vitally stained a number of cells in the cerebral ganglion and the nerve tracts extending from the ganglion. Electron microscopy showed that many neurons contained electron‐dense vesicles. The close association of the fluorescing, amine‐containing nerve tracts with the sensory bulbs suggests that they may play a functional role in sensory reception and transmission in M. dubius. This is the first report on the presence of biogenic amines in the Acanthocephala.
Retinal illumination produces synaptic inhibition of a neurosecretory organ in the crayfish, pacifastacus leniusculus (Dana)
Authors: Kirk Mark D. , Prugh John I. , Glantz Raymon M.
Published: January 2005

We have identified a cluster of neurosecretory cells in the crayfish eyestalk that possess dendrites in the second optic neuropil (Medulla) and project axons to the first optic neuropil (Lamina). Illumination of the ipsilateral retina produces a synaptic inhibition of these cells that is mimicked by iontophoresis of gamma‐aminobutyric acid within the medullary neuropil. The neurosecretory nature of the cells, the efferent projection of their axons, and the strong inhibition of their spiking activity upon retinal illumination suggest that they may be involved in the feedback control of dark adaptation and/or circadian changes in visual sensitivity.
Leg position learning by an insect: II. Motor strategies underlying learned leg extension
Authors: Forman Robin R. , Zill Sasha N.
Published: January 2005

The patterns of myographic activity in the flexor and extensor tibiae muscles of the locust which accompany learned tibial extension were examined. Three distinct motor strategies were identified: (1) repeated flexion‐extension movements, each of which resulted in a momentary excursion beyond the required, pre‐set joint angle (demand angle) and in sum met the criterion for learning; (2) changes in basic muscle tonus, which resulted in maintained shifts in tibial position without discernible myographic activity; (3) tonic activity in the single slow excitatory motoneuron of the extensor tibiae (SETi) which produced maintained tibial extension. These strategies were selectively employed depending on the particular range of joint angle required. These strategies were compared and their effectiveness evaluated using a variety of behavioral criteria. Neuronal mechanisms which might underlie each of these strategies are discussed.
The nature of the chick's magnesium‐sensitive retinal spreading depression
Authors: van Harreveld A.
Published: January 2005

Spreading depression (SD) in the chick retina is completely suppressed by 10 mM MgCl2 in the bathing solution (Mg‐sensitive SD). However, after increasing the KCl concentration in the Mg solution to values between 10 and 20 mM the retina can again exhibit SDs (Mg‐insensitive SD). It has been postulated that the Mg‐sensitive SD is a glutamatergic phenomenon. This is supported by the effect of four gl(utamate)‐antagonists—L‐proline, glutamic acid diethyl ester (GDEE), D‐α‐aminoadipate (D‐AA), and 2‐amino‐4‐phosphonobutyrate (APB)—which all suppressed this type of SD. It was suggested that this effect is due to competitive binding of glutamate involved in the Mg‐sensitive SD and the gl‐antagonist to glutamate receptors. The suppression of SD could be reversed by washing the preparation in a physiologic salt solution. The gl‐antagonists in relatively high concentrations had a cytotoxic effect which, when severe, suppressed SD and prevented the recovery of this phenomenon by washing the compound out of the tissue.

The compounds examined had, in addition to their gl‐antagonistic properties, a gl‐agonistic effect, which was postulated to enhance the Na+ permeability of neural membranes resulting in a release of K+ into the extracellular space. In preparations bathed in 10 mM MgCl2 (which suppresses Mg‐sensitive SDs) the four compounds investigated promoted Mg‐insensitive SDs supposedly when the extracellular K+ concentration reached values between 10 and 20 mequiv.
Dorsal unpaired median neurons, and ventral bilaterally paired neurons, project to a visceral muscle in an insect
Authors: Lange Angela B. , Orchard Ian
Published: January 2005

Cobalt backfilling, Lucifer yellow injection and neurophysiological recordings have been used to identify the neurons, in particular dorsal unpaired median neurons, which contribute axons to the oviducal muscles of the locust Locusta migratoria. A total of eight neurons within the VIIth abdominal ganglion have axons passing to the oviducts. Three pairs of bilaterally symmetrical neurons have ventrally located cell bodies. One neuron from each pair projects to the left side of the oviducts and the other the right side of the oviducts. These cells lie ipsilateral to the nerve root through which they exit. The neuropilar branches are intraganglionic and lie mainly in the ipsilateral neuropile, however one of the neurons from each side possesses a giant process, reaching 10 μm in diameter, which passes dorsally to the contralateral side of the ganglion.

The other two neurons are dorsal unpaired median neurons, and have large cell bodies which lie at the posterior end of the ganglion. Lucifer yellow injection into these two dorsal unpaired median neurons reveals a single neurite passing anteriorly from the cell body which bifurcates into two bilaterally symmetrical processes which exit to the oviducts through both the left and right sternal roots. Similar to other identified dorsal unpaired median neurons, the cell bodies stain with neutral red and can support overshooting action potentials. The possibility that these two cells contain octopamine is discussed.
Morphology of two pairs of identified peptidergic neurons in the Buccal ganglia of the mollusc Tritonia diomedea
Authors: Masinovsky Boris , Lloyd Philip E. , Willows A. O. Dennis
Published: January 2005

The morphology of two pairs of identified peptidergic neurons (B11 and B12) located in the buccal ganglia of Tritonia diomedea was described. Both pairs of neurons contained a large quantity of a small cardioactive peptide (SCP) in their somata. One of the pairs (B11), the large dorsal white cells, contained ACh in their somata along with SCP.

Both pairs of cells appeared white in live preparations under epi‐illumination. Each B11 and B12 was a unipolar neuron and sent its major axonal branch through the ipsilateral gastro‐esophageal nerve to the gut. In addition, B12 sent a small branch to the contralateral buccal ganglion.

A characteristic feature of both neuron pairs was their vesicular content. Three types of vesicles were observed in B11. Vesicles with electron‐lucent core (LCV) and electron‐dense core (DCV) were found in the somata. The axon hillock and the beginning of axon contained vesicles with variable electron dense core (VDCV) in addition to LCV and DCV. The ratio of DCV: LCV: VDCV changed from 5:95:0 for the perinuclear cytoplasm to 8:55:37 for the beginning of axon. The average maximum diameters were 97 ± 23 nm for DCV, 103 ± 32 nm for LCV and 106 ± 29 nm for VDCV.

B12 somata contained DCV (average maximum diameter 100 ± 26 nm), LCV (109 ± 23 nm) and elliptical vesicles with eccentric electron‐opaque core (115 ± 20 nm).
Evidence for octopaminergic modulation of an insect visceral muscle
Authors: Orchard Ian , Lange Angela B.
Published: January 2005

Two dorsal unpaired median neurons (DUMOV1 and DUMOV2) lying in the posterior region of the VIIth abdominal ganglion of Locusta migratoria have axons which project to the muscles of the oviducts. This study reports the presence of octopamine within isolated DUMOV cell bodies, as well as in the oviducal nerve and innervated oviducal muscle. Individual cell bodies were pooled and found to contain about 0.34 pmol of octopamine per cell body giving an approximate value of 1.27 mM octopamine. Octopamine is concentrated within the area of oviducal muscle which receives DUMOV axons.

Pharmacological studies reveal that the amplitude of neurally‐evoked contractions of the oviducal muscle is reduced in a dose‐dependent manner by octopamine, with threshold lying between 5 × 10−10 M and 7 × 10−9M. The receptors for this response show a specificity for octopamine and synephrine, with an order of potency being octopamine = synephrine > metanephrine > tyramine > dopamine.

The presence of octopamine throughout this neural pathway, coupled with the demonstration of octopaminergic modulation of muscular contraction, supports the hypothesis that octopamine serves a physiological role in this visceral system.
Donor‐recipient interconnections between giant nerve fibers in transplanted ventral nerve cords of earthworms
Authors: Vining E. P. , Drewes C. D.
Published: January 2005

Twelve segments of ventral nerve cord (VNC) from donor earthworms, Eisenia foetida, were transplanted into recipient worms from which a comparable length of VNC had been removed. Within the first few days after transplantation, bud‐like formations, containing outgrowths of the giant nerve fibers, were evident at the ends of transplanted and recipient VNC. Morphological and electrophysiological evidence indicated that by 4–10 days after transplantation, medial (MGF) and lateral (LGF) giant fibers within the transplanted VNC formed cell‐specific connections with their counterparts in the recipient VNC. Although the diameters of the giant fiber connections in the transplant‐recipient junctions were often larger than normal, spike conduction across the junction was initially slow (approximately 1.0 m/s) but gradually increased over the next 2–3 weeks. Within the transplant, giant fibers were initially normal in appearance, but spike conduction was slow (1–2 m/s). During the next few weeks velocities increased by as much as fourfold and then stabilized for the next several months. However, by 4–5 weeks after transplantation, giant fiber morphology within the transplant was altered significantly, as indicated by the formation of numerous branch‐like extensions along the length of each giant fiber. By 9–10 months there were further morphological changes in the transplant, as indicated by decreased branching of the giant fibers and altered neuropile. Despite these morphological changes, through‐conduction of giant fiber spikes remained reliable.
Innervation of the limb accessory flexor muscle in several decapod crustaceans. I. Anatomy
Authors: Govind C. K. , Wiens T. J.
Published: January 2005

The innervation of the accessory flexor muscle of the limbs of several decapod crustaceans was studied by means of vital staining, with methylene blue and electron microscopy. Three patterns of innervation were found. In the first pattern, the distal (DAFM) and proximal (PAFM) heads of the accessory flexor muscle were supplied by two axons (a thick and a thin) which travel in a private nerve along the length of the merus. This pattern was found in the crab (Cancer) and the lobster (Homarus), and conforms to the classical pattern established in the literature. In the second pattern, the nerve to the DAFM is made up of conjoined branches of the flexor and accessory flexor nerves. Consequently, the DAFM receives at least five axons in the portunid crabs, Carcinus, Callinectes, and Ovalipes, and occasionally six axons in Ovalipes. The PAFM in those portunids receives the usual two axons. In the third pattern, based on preliminary observations on the grapsid crab, Pachygrapsus, “super‐innervation” of the accessory flexor muscle appears to include not only five axons to the DAFM but also at least three to the PAFM. In all species, methylene blue staining of the axon terminations revealed a regular pattern of blebs which are thought to correspond to synaptic terminals as revealed by electron microscopy.
Dietary choline augments associative memory function in Limax maximus
Authors: Sahley C. L. , Barry S. R. , Gelperin A.
Published: January 2005

Previous clinical and experimental work has shown that increased dietary intake of choline elevates blood choline and brain acetylcholine levels. This change in neuronal acetylcholine concentration may augment learning and memory functions. We tested this prediction using the mollusc Limax maximus, an animal which can be readily conditioned to avoid food odors. In our experiments, initial learning of a food avoidance task was not augmented by the high choline diet. However, the duration of memory retention was prolonged. In previous studies, we have shown that intake of the choline enriched diet significantly increases blood choline and amplifies transmission at an identified cholinergic synapse in Limax. Together, these results support the involvement of cholinergic synapses in the memory retention mechanism.
Control of the development of the ipsilateral retinothalamic projection in Xenopus laevis by thyroxine: Results and speculation
Authors: Hoskins Sally G.
Published: January 2005

The ipsilateral retinothalamic projection of the frog Xenopus laevis is formed by the axons of a subset of retinal ganglion cells which are found throughout peripheral and non‐nasodorsal retina. Unlike the crossed retinotectal and retinothalamic projections, which begin to form during early embryonic stages, the ipsilateral projection does not begin to develop until late in tadpole life, at stages when thyroxine first becomes detectable in the circulation. Blocking the production of thyroid hormone in tadpoles prevents the development of the ipsilateral projection, in a reversible manner. Intraocular injection of thyroxine can “rescue” the development of the projection in tadpoles which otherwise remain premetamorphic. In addition, the projection from one eye of a metamorphically‐blocked tadpole can be induced to form by an intraocular injection of thyroxine at a dose which has no detectable effect on retinal development in the other, untreated eye. These results indicate that the development of the ipsilateral retinothalamic projection is dependent upon thyroxine, and strongly suggest that the hormone acts at the level of the eye, rather than at the optic chiasm or thalamic target, to bring about the development of a new pathway. A number of ways in which thyroxine might act in the system are discussed.
A model of pattern generation of cockroach walking reconsidered
Authors: Zill Sasha N.
Published: January 2005

Cockroaches that have been decapitated or that have cut thoracic connectives can show rhythmic bursting in motoneurons to intrinsic leg muscles. These preparations have been studied as models for walking and to evaluate the functions of leg proprioceptors. The present study demonstrates that (1) headless cockroaches walk extremely poorly and slowly with considerable discoordination of motoneuronal activity, (2) these preparations show rhythmic motoneuron bursting that is similar to righting responses (attempts to turn upright) of intact animals when placed on their backs, and (3) bursting is inhibited when a headless animal is turned or turns itself upright. Thus, rhythmic motoneuron activity of these preparations is most probably attempted righting rather than walking. It is concluded that the headless cockroach is useful for understanding the motor mechanisms underlying righting and walking but is not of value in assessing the functions of proprioceptive feedback.
A genetic analysis of glutamaterigic function in Drosophila
Authors: Chase Bruce A. , Kankel Douglas R.
Published: January 2005

Neurotransmitters are essential for communication between neurons and hence are vital in the overall integrative functioning of the nervous system. Previous work on acetylcholine metabolism in the fruit fly, Drosophila melanogaster, has also raised the possibility that transmitter metabolism may play a prominent role in either the achievement or maintenance of the normal structure of the central nervous system in this species. Unfortunately, acetylcholine is rather poorly characterized as a neurotransmitter in Drosophila; consequently, we have begun an analysis of the role of glutamate (probably the best characterized transmitter in this organism) in the formation and/or maintenance of nervous system structure. We present here the results of a series of preliminary analyses. (1) To suggest where glutamatergic function may be localized, an examination of the spatial distribution of high affinity [3H]‐glutamate binding sites are presented. (2) We present the results of an analysis of the spatial and temporal distribution of enzymatic activities thought to be important in the regulation of transmitter‐glutamate pools (i.e., glutamate oxaloacetic transaminase, glutaminase, and glutamate dehydrogenase). (3) To begin to examine whether mutations in any of these functions are capable of affecting glutamaterigic activity, we present the results of an initial genetic analysis of one enzymatic function, glutamate oxaloacetic transaminase (GOT), chosen because of its differential distribution within the adult central nervous system and musculature.
Ontogenetic changes in the pattern of androgen accumulation in song‐control nuclei of male zebra finches
Authors: Bottjer Sarah W.
Published: January 2005

The present study examines the development of androgen accumulation in cells of two brain nuclei that are involved in controlling vocal behavior in zebra finches (Poephila guttata). HVc (caudal nucleus of the ventral hyperstriatum) is involved with vocal production in adult birds, and MAN (magnocellular nucleus of the anterior neostriatum) is involved with the initial ability to learn song. In both of these nuclei there is an increase in the proportion of cells that are labeled by systemic injections of tritiated dihydrotestosterone in juvenile male zebra finches during the time when production of song is becoming stereotyped (25–60 days). Within MAN there is an overall loss of cells during this time, such that the absolute number of androgen target cells in MAN remains at a constant level. However, it does not appear to be the case that unlabeled cells are selectively lost from MAN (see the text). Rather it appears that both labeled and unlabeled cells are lost, and the absolute number of labeled cells is maintained at a constant level via recruitment of additional labeled cells from the unlabeled population (i.e., some MAN cells that are unlabeled in young birds become labeled in older birds). In line with this hypothesis, there is a large increase in the density of labeling in individual MAN cells, indicating that these cells have an enhanced ability to concentrate androgen. In contrast to the situation in MAN, there is an increase in the overall number of cells within HVc during this time; this increase in total cell number combines with the increased proportion of labeled cells such that the absolute number of androgen target cells in HVc increases threefold. The ability of individual HVc cells to accumulate androgen remains constant. The relationship of these changes in the pattern of androgen accumulation to other aspects of neural and behavioral development related to song in zebra finches are discussed.
Synaptic competition and the persistence of polyneuronal innervation at frog neuromuscular junctions
Authors: Werle Michael J. , Herrera Albert A.
Published: January 2005

Mechanisms governing the elimination of polyneuronal innervation were examined by correlating the morphology and physiology of competing nerve terminals at identified dually innervated neuromuscular junctions in sartorius muscles of adult frogs (Rana pipiens). Synaptic efficacy (endplate potential amplitude per unit nerve terminal length) was presumed to reflect the ability of a terminal to compete for synaptic space. The synaptic efficacies of two terminals at the same synaptic site were found to be surprisingly equal, with a median difference of 33%. Much more variation would be expected if dually innervated junctions were randomly innervated by pairs of terminals having the same range of synaptic efficacy as that found at singly innervated junctions in the same muscle. This finding supports the hypothesis that the weaker input is elimianted from dually innervated junctions when there is a large discrepancy in competitive efficacy, and that both inputs may persist if competitive efficacies are relatively equal. We also tested but failed to find support for the hypothesis that spatial proximity between competing terminals intensifies competition for synaptic space during synapse elimination.
A novel serotonin‐immunoreactive neuron in the antennal lobe of the sphinx moth Manduca sexta persists throughout postembryonic life
Authors: Kent Karla S. , Hoskins Sally G. , Hildebrand John G.
Published: January 2005

A single serotonin‐immunoreactive neuron in the antennal lobe (AL) of the brain of the sphinx moth Manduca sexta is present in larval, pupal, and adult stages. This neuron has a neurite that extends to the contralateral AL, where it forms sparse arborizations in each glomerulus. Other neurites from this neuron project into the ipsilateral and contralateral protocerebrum. This cell is morphologically very different from other neurons previously characterized in the adult AL. The neuron maintains the same basic profile in the adult as in the larva, although fine processes such as the arborizations within the AL neuropil appear to be restructured to conform to the larger, more anatomically diffentiated regions of the adult brain.
Regeneration studies on a crayfish neuromuscular system. I. Connectivity changes after intersegmental nerve transplants
Authors: Worden Mary Kate , Hwang Ji‐Chuu , Vélez Samuel J.
Published: January 2005

The superficial flexor muscles of the crayfish are a neuromuscular system of a few muscle cells innervated by six neurons in a precise position‐dependent pattern. The neurons are capable of regenerating their normal connectivity patterns within a short span of time when conditions are favorable. The superficial flexor muscles of the second and third segments, despite their similarities in neuronal and muscle cell size and number, have distinctive connectivity patterns; some homologous neurons form similar patterns but other homologous neurons form patterns that are reversed between segments. We transplanted each segment's nerve into each other's muscle in order to observe regeneration of the nerves into a target area that differed in connectivity patterns from their original muscle. During the first weeks of regeneration all neurons formed a connectivity pattern with more connections medially and declining connections laterally, a pattern determined bythe medial location of the nerve transplant. This pattern is maintained for most of the neurons, but for some there is an eventual reduction in medial connections as maximum synapse formation shifts to the lateral muscle fibers. Three of the eight neurons studied were able to regenerate connectivity patterns that corresponded to their segment of origin and not to their host muscle. This suggests that intersegmental muscle differences are not influencing the formation of these connectivity patterns, so the neurons will follow their inherent synaptogenesis program.
Regeneration studies on a crayfish neuromuscular system. II. Effect of changing the nerve entry point into the muscle field on the gradient of innervation
Authors: Goransson Leslie G. , Hunt William P. , Vélez Samuel J.
Published: January 2005

The superficial flexor muscle of the crayfish is a neuromuscular system in which the neurons form position‐dependent connectivity patterns with the muscle fibers. This system could be formed with the help of a single medial‐to‐lateral gradient during development that embodies positional information. To test this gradient hypothesis we changed the nerve's normal medial entrypoint into the muscle by transplanting it to the middle ofthe muscle sheet. When all the muscle fibers were present in the target area, most of the neurons studied passed through a stage during regeneration in which they showed preference for either medial or lateral synapse formation. Those neurons that in normal animals innervated preferentially the medial fibers showed a medial preference for new contacts; the neuron that normally innervated the lateral fibers showed a lateral preference for new contacts; the neuron that normally innervated everywhere regenerated equallywell into both medial and lateral fibers. Therefore, theseneurons are able to detect information regarding their position within the muscle mass and respond to it by preferential synapse formation. The effect of a positional gradient could not be detected when half of the target field was removed prior to regeneration. In this instance, the neuron that innervated the missing target area now regenerated to almost all the available fibers. It is suggested that the interplay of positional cues with other factors at different points in time could determine the final connectivity patterns formed by these cells.
Fibronectin‐like immunoreactivity in Helisoma buccal ganglia: Evidence that an endogenous fibronectin‐like molecule promotes neurite outgrowth
Authors: Mattson Mark P. , Kater Stanley B.
Published: January 2005

We examined the distribution of fibronectin‐like (FNL) immunoreactivity associated with intact buccal ganglia, cell‐cultured buccal ganglia neurons and nonneuronal cells, and brain‐conditioned medium from the snail Helisoma. In addition, the possible roles of fibronectin in the regulation of neurite outgrowth were studied. Immunofluorescent staining for FNL antigens revealed intense staining in patches and fibrous arrays over the connective tissue sheaths of buccal ganglia and nerve trunks. Within the ganglia, heavy staining was seen surrounding neurons and in track‐like arrangements. In cell cultures, specific staining was associated with nonneuronal cell surfaces and to a lesser degree with the surface of identified neurons. In addition, a noncellular, substrate‐bound component of brain‐conditioned medium displayed FNL immunoreactivity. Since cultured Helisoma neurons require a substrate‐associated, brain‐derived conditioning factor (CF) in order to elaborate neurites with motile growth cones, we tested whether the FNL immunoreactive substance might act as a neuritotropic agent. Fibronectin antiserum suppressed, in a dose‐dependent manner, the CF‐induced sprouting of identified neurons in isolated cell culture. When added at increasing concentrations to neurons already growing in response to CF, fibronectin antiserum exerted a biphasic effect on neurite elongation; outgrowth was accelerated at low, but inhibited at high, antiserum concentrations. In contrast, growth cone structures associated with motility (filopodia and lamellipodia) were progressively reduced by increasing levels of antiserum. A short peptide derived from fibronectin's cell‐binding domain (Arg‐Gly‐Asp‐Ser) also greatly reduced neurite outgrowth. The combined results of this study indicate an abundance of FNL immunoreactive molecules within the CNS of Helisoma, their probable production by nonneuronal cells, and their function as a substrate‐associated component of CF which promotes growth cone filopodial and lamellipodial activity.
Song‐related brain regions in the red‐winged blackbird are affected by sex and season but not repertoire size
Authors: Kirn John R. , Clower Robert P. , Kroodsma Donald E. , Devoogd Timothy J.
Published: January 2005

Previous work in songbirds has delimited a neural system responsible for song production and control. Earlier studies have suggested that functional capacity in the song system may be related to the mass of the system in an animal's brain, and that adult plasticity in this neural system may be related to adult capacity for behavioral modification. We now test these hypotheses in adult red‐winged blackbirds (Agelaius phoeniceus), a species in which song is produced primarily by males, new song types are added to the male's repertoire in adulthood, and there are substantial differences among males in song complexity. We find that the song system in males is much larger than in females. Song system nuclei become smaller in both sexes as the animals experience shorter days. We do not find any association between repertoire size and size of any of the song system structures examined. Thus, although sex differences in song may be related to differences between sexes in the mass of song system structures, individual differences in song do not appear to be directly related to mass within males. Seasonal change in song system structures in male redwings is consistent with there being a relation between adult plasticity in anatomy and in behavior; the large seasonal change in these structures in females suggests large seasonal changes in the function of these nuclei.