bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurotrophic regulation of GABA receptors at a crayfish inhibitory synapse
Authors: Craelius William , Tiberio Angela , Pomerantz Jeffrey 
Published: January 2005

AbstractExperiments were done on the inhibitory synapse of crayfish tonic muscle receptor organs (MROs) to determine whether gamma‐aminobutyric acid (GABA) receptors would be affected by denervation or axotomy. It was found that severing the dorsal nerve containing the MRO sensory and inhibitory neurons usually induced, in 30 days or less, a dramatic transformation in the responses of MROs to ionophoretically applied GABA. In contrast to normal MROs which show only inhibitory responses to GABA, transformed MROs were substantially depolarized and excited by GABA application to numerous points found on the axon, soma, and dendrites. Interspersed among the points of excitation, normal inhibitory points could still be found on the transformed cells. The results suggested that chronic lesions can induce structural changes in GABA receptors, whereby the Cl− ionophore is replaced by a cationic channel. It was possible to compare the effects of postsynaptic axotomy alone with those of postsynaptic plus presynaptic axotomy by testing MROs from animals whose ventral nerve cord was sectioned. These experiments suggested that interruption of the presynaptic neuron is an important factor in the transformation. It was not determined whether complete degeneration of the inhibitory synapse is necessary for the transformation, but the rapidity of the effect, coupled with the probability of long‐term survival of synaptic contacts, suggested that complete degeneration was not necessary. Similarities were found in the GABA responses of transformed MROs and those MROs which normally receive no innervation, which are located in the sixth abdominal segment. These results support the idea that trophic regulation from inhibitory neurons is a factor in stabilizing the association of the Cl− ionophore with GABA receptors.
Modifications of dynamic and static behavior by small‐length perturbations in crayfish stretch receptor organs
Authors: Buño W. , Bustamante J. , Fuentes J. 
Published: January 2005

AbstractTo investigate whether static and dynamic sensitivities of slowly and rapidly adapting stretch receptor organs (SAO and RAO, respectively) of crayfish are different when perturbed compared with those in conventional laboratory experiments, receptors were submitted to ramplike length changes of different velocities separated by long‐duration, constant lengths of different values. They were perturbed at random by fast, small‐amplitude length variations called “jitter.” First‐order afferent discharges were recorded extracellularly. Quantifications involved the separate estimation of static and dynamic response components. In the SAO, jitter (1) augmented the static sensitivity, (2) decreased the dynamic sensitivity, (3) simplified response profiles by decreasing nonlinearities and increasing transduction fidelity in terms of coding length. In the RAO, jitter (1) changed the behavior from phasic to tonic with length sensitivity, (2) decreased the dynamic sensitivity to values close to those of the unperturbed SAO, (3) increased transduction fidelity for stimulus length and decreased nonlinearities. Perturbation effects suggest that differences between SAO and RAO are more quantitative than qualitative. Moreover, they have general implications and are relevant to other mechanoreceptors at other levels in the CNS.
Possible temperature‐dependent blockage of synaptic vesicle recycling induced by a single gene mutation in drosophila
Authors: Kosaka Toshio , Ikeda Kazuo 
Published: January 2005

AbstractThe temperature‐sensitive Drosophila mutant, shibirets1 (shi), has been shown to exhibit a reversible block in synaptic transmission at 30°C. Various synaptic terminals (neuromuscular, sensory, central) of this mutant were observed by electron microscopy. At 19°C, all terminals of shi showed essentially the same structural features as those of wild‐type (Oregon‐R) flies, while at 30°C (5 or 10 min of exposure) shi terminals exhibited various structural changes not seen in the wild type. The major structural change observed in all of the various types of terminals was the accumulation of many pitlike structures on the plasma membrane near presynaptic sites. These structures consisted of a spherical head portion, about 50–100 nm in diameter, and a cylindrical neck portion, about 20 nm long and 20–25 nm in diameter. The neck portion was surrounded by a kind of cytoplasmic dense material, about 10 nm thick, reminiscent of a “collar.” Thus, these pits are referred to as “collared pits.” Similar kinds of pits were observed, although very rarely, in wild‐type flies at 19 and 30°C and in shi flies at 19°C. In addition, various degrees of vesicle depletion, and an increase in membranous structures (infoldings and cisternalike or tubulelike structures) often accompanied pit formation. The possibility that these pits are the result of a blocked step in the endocytotic process, which in turn causes vesicle depletion as exocytosis proceeds, is discussed.
Elicitation and abrupt termination of behaviorally significant catchlike tension in a primitive insect
Authors: Hoyle Graham , Field Laurence H. 
Published: January 2005

AbstractSustained steady contractural or catchlike tension (CT) occurs in the metathoracic extensor tibiae muscle of the primitive insect the weta (Orthoptera: Stenopelmatidae) during its characteristic leg‐extension defense behavior or following leg‐position conditioning. Similar action occurs occasionally in semi‐intact preparations and is abruptly turned off by a single peripheral inhibitory impulse. These phenomena were reproduced routinely by first infusing saline containing 10−8M (or stronger) octopamine into the muscle for 12 min, and then stimulating the slow excitatory motor neuron SETi with a brief burst. Direct stimulation of the dorsal unpaired median neuron, innervating the extensor tibiae (DUMETi) prior to SETi stimulation, also led to CT. Both octopamine and DUMETi markedly enhanced the tension developed in response to a burst of impulses in SETi.
Innervation and motor patterns of the abdominal superficial flexor muscles in larval lobsters
Authors: Kirk Mark D. , Govind C. K. 
Published: January 2005

AbstractThe pattern of innervation and motor program of the abdominal superficial flexor muscle was investigated electrophysiologically in larval lobsters (Homarus americanus). The muscle receives both excitatory and inhibitory innervation in the larval as well as in the embryonic stages. Individual muscle fibers receive a single inhibitory neuron (f5) and a maximum of three excitors. Based on spike heights these axons belong to either the small (f1 or f2) or large (f3, f4) motoneurons. While the small axons preferentially innervate the medial muscle fibers the large axons innervate medial as well as lateral fibers. This larval pattern of innervation resembles the pattern in the adult lobster. The resemblance extends to the firing patterns as well with both large and small excitors firing spontaneously. Furthermore, evoked activity in the larvae produces reciprocal (and occasionally cyclical) bursts of excitor and inhibitor neurons denoting abdominal extension and flexion and resembling the firing patterns in adults. Consequently motor programs employed in steering the pelagic larvae are reminiscent of the programs for maintaining posture in the benthic adult lobsters.
Increased regeneration rate in peripheral nerve axons following double lesions: Enhancement of the conditioning lesion phenomenon
Authors: Bisby M. A. , Pollock B. 
Published: January 2005

AbstractThe rate of regeneration of rat sciatic nerve sensory axons was measured using the pinch‐reflex test method, and confirmed by studying the transport of labelled protein into the regenerating axons. For nerves receiving a single test crush lesion the rate was 4.02 ± 0.03 (SE) mm/day. For nerves with a conditioning lesion made at the knee seven days prior to the test lesion at the hip the rate was 5.73 ± 0.06 mm/day, and for nerves where both conditioning and test lesions were made at the same site (hip or knee) but separated by seven days, the rate was 6.76 ± 0.04 mm/day, a 68% increase over the normal rate, showing that pre‐degeneration of the nerve distal to the site of the test lesion increases the rate of regeneration. It is concluded that the rate of axon regeneration can be influenced by the environment through which the regenerating axons grow.
Activation by dopamine of patterned motor output from the buccal ganglia of Helisoma trivolvis
Authors: Trimble Dorothea L. , Barker David L. 
Published: January 2005

AbstractThe buccal ganglia of the snail, Helisoma trivolvis, contain an intrinsic system of dopamine‐containing neurons (Trimble, Barker, and Bullard, 1983). Dopamine, when bath applied to the isolated buccal ganglia, activates patterned motor output in a dose‐dependent fashion. Haloperidol blocks the activating effect of dopamine, but the similar activation evoked by serotonin is not blocked by haloperidol. We suggest that there are two separate mechanisms for activating patterned motor output from the buccal ganglia. One is serotonergic, emanating from identified cerebral ganglion cells (Granzow and Kater, 1977), while the other is dopaminergic, involving neurons intrinsic to the buccal ganglia.
Cholinergic receptors in the Aplysia gill
Authors: Weiss Sam , Goldberg Jeff I. , Edstrom Jon P. , Lukowiak Ken 
Published: January 2005

AbstractAcetylcholine has been suggested as a neurotransmitter released in the Aplysia gill by peripheral afferents of central neurons and by peripheral neurons within the gill. The perfused gill, isolated from the abdominal ganglion, was examined. At concentrations greater than 1 μM, acetylcholine elicited a slowly developing tonic contraction of the afferent vein that reversed upon washout. This effect was observed on both quiescent and active preparations. At concentrations less than 1 μM, acetylcholine perfusion resulted in a reduction of gill tone. The excitatory effect of acetylcholine was reduced 80 and 60% by the cholinergic antagonists atropine and hexamethonium, respectively. The acetylcholine‐evoked contraction was potentiated 2.5‐fold when curare was coinfused. Carbachol did not mimic the excitatory effects of acetylcholine. At all concentrations examined (1–100 μM), carbachol infusion reduced baseline tension, the amplitude of spontaneous contractions and contractions evoked by FMRFamide and dopamine. Contractions evoked by perfusion of p‐chlorophenylthiocyclic AMP were greatly reduced when carbachol was added to the perfusate. Further addition of curare reversibly blocked carbachol inhibition of the cyclic AMP%evoked contractions. These finding suggest that excitatory and inhibitory cholinergic receptors are involved in the regulation of gill contractile behavior by acetylcholine.
Sensitivity of Aplysia neurons in primary culture to putative neurotransmitters
Authors: Bodmer Rolf , Levitan Irwin B. 
Published: January 2005

AbstractAplysia neurons grown in primary cell culture (Dagan and Levitan, 1981) were exposed to the putative neurotransmitters acetylcholine and serotonin by local iontophoretic application, and changes in membrane potential or voltage clamp currents were examined. It was found that 47% of the neurons were sensitive to cholinergic agonists, 14% to serotonin, and 9% responded to both. Responses could be recorded upon application of the transmitters to the cell bodies as well as along the regenerated neurites. An identified group of neurons, the neurosecretory bag cells, exhibited similar responses to cholinergic agonists in culture and in situ. Pleural medial neurons exhibited cholinergic responses in culture similar to those previously reported in situ. Thus neurotransmitter receptor/ion channel complexes characteristic for a specific cell type in the intact ganglion are also present on this cell type in culture.
Central nervous sensitization and dishabituation of reflex action in an insect by the neuromodulator octopamine
Authors: Sombati Sompong , Hoyle Graham 
Published: January 2005

AbstractHabituation of excitatory synaptic inputs onto identified motor neurons of the locust metathoracic ganglion, driven electrically and by natural stimuli, was examined using intracellular recording. Rapid progressive reduction in amplitude of EPSPs from a variety of inputs onto fast‐type motor neurons occurred. The habituated EPSPs were quickly dishabituated by iontophoretic release of octopamine from a microelectrode into the neuropilar region of presumed synaptic action. The zone within which release was effective for a given neuron was narrowly‐defined. With larger amounts of octopamine applied at a sensitive site the EPSP became larger than normal, and in many instances action potentials were initiated by the sensitized response. Very small EPSPs onto a motor neuron, which were associated with proprioceptive feedback, and which were originally too small to be detected above the noise, were potentiated to a level of several mV by the iontophoresed octopamine. A DUM neuron (presumed to be octopaminergic) was found, whose direct stimulation was followed by a strong dishabituating and sensitizing action leading to spikes, of inputs to an identified flexor tibiae motor neuron. The action and its time course were closely similar to those evoked by octopamine iontophoresed into the neuropil in the region of synaptic inputs to the motor neuron. It is concluded that DUM (octopaminergic) neurons exert large potentiating actions on central neuronal excitatory synaptic transmission in locusts.
Neural control of behavioral responses in the nudibranch mollusc Phestilla sibogae
Authors: Willows A. O. Dennis 
Published: January 2005

AbstractThe tropical aeoliacean nudibranch Phestilla sibogae, has a number of large and reidentifiable neurons in its centrally located cerebral‐pedal‐pleural ganglion complex. In studies involving nearly intact animal preparations, neurons were identified which control specific movements of the dorsal cerata, the oral veil tentacles, and the margins of the foot. Responses of neurons to mechanical vibrations in the environment, and responses to light not mediated by the eyes are described. Finally, a pair of large cerebral neurons are identified that are superficially similar in structure, location, and function to the metacerebral giants found in several other opisthobranchs. These neurons are electrically coupled and control stereotyped movements of the mouth. These anatomical and neurophysiological features, when coupled with the fact that the generation time of Phestilla (30 days) is comparable to that of Drosophila suggests that this nudibranch may prove useful in combined studies of neurophysiology, behavior and genetics.
The central morphology of the giant interneurons and their spatial relationship with the thoracic motorneurons in the cockroach, Periplaneta americana (insecta)
Authors: Collin Shaun P. 
Published: January 2005

AbstractThree groups of giant fibers are found in the cockroach ventral nerve cord. A latero‐dorsal group (dorsal GIs), a latero‐ventral group (ventral GIs) and a medio‐ventral group. The morphology of all three groups of fibers within the thoracic ganglia is described. The morphology of the dorsal and ventral GI pathways in the abdominal and suboesophageal ganglia is also described. The projection patterns of the neurons in each ganglion are remarkably similar which suggests a common function. When motorneurons 5rl (depressor) and 6Br4 (levator) are stained simultaneously with the dorsal and ventral GI groups, some branches from both motor and giant neurons converge. The branching of the remaining medio‐ventral group of fibers and their proximity to areas receiving motorneuronal input suggests that these are the small diameter axons described by Dagan and Parnas (1970).
Morphological and physiological properties of the giant interneuron of the hermit crab (Pagurus pollicaris)
Authors: Stephens Philip J. 
Published: January 2005

AbstractThe physiological and morphological properties of the giant interneurons in the hermit crab Pagurus pollicaris are described. The cell bodies are located anteriorly in the supraesophageal ganglion, close to the mid‐line. Each cell sends a neurite posteriorly and then laterally, so that they cross over in the center of the ganglion. Each axon then branches: one branch runs laterally while the other travels posteriorly and leaves the ganglion in the circumesophageal connective on the side contralateral to the cell body. The giant axons travel in the circumesophageal connectives and through the thoracic and abdominal ganglia without branching. Each giant axon makes synaptic contact with its ipsilateral giant abdominal flexor motor neuron and with a second flexor motor neuron that has its axon in the contralateral third root.In the supraesophageal ganglion there is a bidirectional synapse between the two giant interneurons. Intracellular recordings from the giant axons show that there is a delay of 0.5 to 0.75 ms that cannot be accounted for by spike propagation along the axons, and may be accounted for by a chemical synapse between the giant interneurons.
Effect of early malnutrition on dynamic properties of axodendritic synapses in the rat prefrontal cortex
Authors: Hernández A. , Ruiz S. , Pérez H. , Soto‐Moyano R. 
Published: January 2005

AbstractThe influence of early protein–calorie malnutrition on synaptic transmission in the rat prefrontal cortex was studied by evoking direct cortical responses with different trains of threshold electrical pulses. Malnutrition resulted in a requirement for increased pulse train stimulating current, reflecting a diminished release of neurotransmitter from the preterminal endings. In addition there was an increase in the time constant of pyramidal cells, indicating that axodendritic synapses have a disability for integrating high frequency inputs at the post synaptic level. It is concluded that early malnutrition alters dynamic properties of axodentritic synapses at both the pre‐ and the postsynaptic levels.
Modulatory effects of proctolin on a crab ventilatory muscle
Authors: Mercier A. Joffre , Wilkens Jerrel L. 
Published: January 2005

AbstractProctolin enhances nerve‐evoked, phasic contractions of a selected respiratory muscle of the shore crab, Carcinus maenas, but has no effect on muscle tonus. Proctolin also increases the work and power output of this muscle. These effects are functionally appropriate in view of previous reports that proctolin stimulates the ventilatory rhythm. They also suggest that proctolin exerts coordinated modulatory control at the central and peripheral levels of the gill ventilatory system. In contrast, serotonin, dopamine and octopamine have no effect on this muscle.
Steroid control of neuron and muscle development during the metamorphosis of an insect
Authors: Weeks Janis C. , Truman James W. 
Published: January 2005

AbstractInsect metamorphosis is controlled by a small ensemble of developmental hormones including a class of steroids—the ecdysteroids. In the tobacco hornworm, Manduca sexta, the progession from the larval to pupal to adult stages is controlled by the relative blood titers of ecdysteroids and juvenile hormone (JH). The cellular events in the nervous and muscular systems which accompany metamorphosis resemble those of embryonic development, but they occur in an animal which is larger and experimentally more tractable than an embryo. In this paper we review the role of ecdysteroids in directing the metamorphosis of the nervous and muscular systems in Manduca, and how JH modifies the cellular responses to the steroids. In particular, we describe how these hormones control muscle degeneration, changes in the structure and function of identified neurons, and programmed neuron death. One general finding is that interactions between cells (e.g., neurons and their target muscles) are not involved in their hormonal responses, but rather the hormones act independently and in parallel at the different sites. Another key finding is that the critical periods and hormonal requirements for the commitment to a particular differentiative pathway, and the phenotypic expression of that pathway, can differ, and are therefore experimentally separable. Finally, we find that the significance of a hormonal signal (e.g., a rise in blood ecdysteroids) is interpreted differently depending upon the previous history of hormone exposure of a neuron or muscle. This progressive change in the interpretation of hormonal signals is a major mechanism by which a limited number of hormones can orchestrate a complicated phenomenon such as metamorphosis.
Effect of synthetic bag cell and atrial gland peptides on identified nerve cells in Aplysia
Authors: Rock M. K. , Shope S. B. , Blankenship J. E. , Schlesinger D. H. 
Published: January 2005

AbstractWe have examined the effects of peptides on the neuroendocrine bag cells, the R2 neuron and the left upper quadrant (LUQ) neurons of the abdominal ganglion of Aplysia californica. Peptides include those extracted from the atrial gland, a reproductive organ; those released by an afterdischarge of the bag cells; and 2 synthetic peptides: the amidated 9‐amino acid C‐terminal portion of atrial gland peptides A/B/ERH (B26–34), and the 8‐amino acid alpha‐bag cell peptide (α‐BCP1–8). Peptides were applied by superfusion, arterial perfusion, pressure ejection from micropipettes, or by inducing a bag cell afterdischarge.Both α‐BCP1–8 and B26–34 are able to produce a bag cell afterdischarge when applied to the abdominal ganglion but are not as effectively able to trigger the bag cells when applied selectively to the ganglia of the head ring.Peptides released by the bag cells inhibit R2 and LUQ neurons; whereas atrial gland extract mildly excites LUQ neurons and powerfully excites R2. The inhibitory effect of the LUQ cells and R2 following an afterdischarge of the bag cells in mimicked by α‐BCP1–8. The excitatory effect of the atrial gland extract cannot be duplicated with B26–34. Rather, instead of having an excitatory effect on R2 and LUQ cells, B26–34 seems to mimick α‐BCP1–8 and inhibit these neurons. Both peptides produce a membrane conductance increase in R2 and LUQ cells.
Effects of octopamine and forskolin on excitatory junction potentials of developing and adult moth muscle
Authors: Fitch Greg K. , Kammer Ann E. 
Published: January 2005

AbstractIntracellular recordings were made from the dorsal longitudinal muscle of Manduca sexta to determine the effects of development and octopamine on the excitatory junction potential (EJP) produced in response to electrical stimulation of the motor nerve. Observations were made on pharate moths during the last 3 days before eclosion and on adults.In saline, the highest values for EJP amplitude and maximum rate of rise and for resting membrane potential are reached on the nineteenth day of the pupal period, the day the animal ecloses; adult values are slightly lower.In animals of all ages tested, DL‐octopamine (5 × 10−6M) increases EJP amplitude and maximum rate of rise. Increases in amplitude are greater in animals at stage day 17 and 18 than in animals at stage day 19 and adult. Octopamine has no effect on EJP rise time (onset to peak) or recovery time (peak of EJP to 70% recovery). Octopamine causes a hyperpolarization of about 6 mV. The results show that developmental changes in synapse properties are paralleled only in part by changes induced by octopamine. Both development and octopamine increase EJP amplitude and maximum rate of rise, and neither alter rise time. EJP recovery time changes with development but not in response to octopamine.Forskolin (10−4M) mimics the effects of octopamine on day 17 animals. EJP amplitude and maximum rate of rise are inceased by forskolin, and rise time and recovery time are unaffected. Forskolin, like octopamine, causes a 6 mV hyperpolarization of the muscle fiber. These results suggest that octopaminergic modulation at the Manduca sexta dorsal longitudinal neuromuscular junction may be mediated by changes in intracellular levels of cyclic AMP.