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At least 19 recordsLinked to original sources
PubMed1992

Effects of detergents on Ca(2+)-activated neural proteinase activity (calpain) in neural and non-neural tissue: a comparative study.

Calcium activated neutral proteinase (mcalpain) activity was determined in brain and other tissue of rat. More than 60% of the brain mcalpain activity was present in the particulate fraction while only 30% was in cytosol. In contrast, particulate fractions of liver, kidney, muscle, and heart contained about 8-12% of tissue mcalpain activity while 88% was present in cytosol. Removal of the endogenous inhibitor calpastatin increased the tissue mcalpain activity severalfold. Triton X-100 and deoxycholate (DOC) stimulated the neural calpain activity by ten-fold while activity in non-neural tissue was unaffected. Incubation with other detergents, e.g. Triton N-57 and thioglucopyranoside, stimulated brain calpain activity five-fold while Brij-35 did not have any effect. Sodiumdodecylsulphate (SDS), on the other hand, inhibited the enzyme activity. Brain contained the lowest calpain activity compared to non-neural tissue. The calpain activity in muscle, kidney and heart was three-fold greater than liver. Immunoblot identification of the enzyme revealed that calpain was predominantly in the particulate fraction and less in cytosol of brain while it was present mainly in cytosol and less in the pellet fractions of non-neural tissue.

Animals↗
PubMed1991

Specific monosynaptic sensory-motor connections form in the absence of patterned neural activity and motoneuronal cell death.

The importance of neural activity and motoneuronal cell death in the formation of specific synaptic connections between muscle afferents and motoneurons was studied in chick embryos. Patterned neural activity was blocked by applying d-tubocurarine (dtc) chronically to embryos during the period when sensory-motor connections are formed [stages (St) 28-42]. Dtc blocks neurogenic muscle contractions, thereby abolishing any temporal correlation between neural activity in motoneurons and stretch-sensitive afferents. The normal pattern of motoneuronal bursting is also blocked (Landmesser and Szente, 1986), as is motoneuronal cell death (Pittman and Oppenheim, 1979). Dtc applications were started more than 1 d before muscle sensory afferent collaterals make anatomical contact with motoneuronal dendrites and continued until St 38-42, when the pattern of synaptic connectivity was examined by recording synaptic potentials intracellularly from identified lumbosacral motoneurons upon stimulation of identified populations of muscle afferents. In both normal and dtc-treated animals, large monosynaptic excitatory potentials were evoked in homonymous motoneurons (those that supply the same muscle as the sensory afferents) and were often observed in motoneurons that supplied synergistic muscles. Monosynaptic potentials were uncommon in motoneurons supplying antagonistic muscles. The overt patterns of sensory-motor connections in normal and dtc-treated embryos were essentially identical. However, the amplitudes of the composite EPSPs recorded in dtc-treated animals were consistently about twice as large as normal. These observations suggest that neither normal patterns of neuronal activity nor motoneuronal cell death play a large role in determining the specificity of connections between the sensory and motor neurons involved in the stretch reflex.

Afferent Pathways↗
PubMedDate not supplied

Daily changes in neural activation, force-time and relaxation-time characteristics in athletes during very intense training for one week.

Daily changes in neural activation, force-time and relaxation characteristics of the leg extensor muscles were examined in 8 elite strength athletes during a very intense strength training period with two daily sessions for one week. The maximal neural activation (integrated EMG) of the muscles and their maximal isometric extension force remained statistically unaltered during the entire experimental period. Average integrated EMG of the muscles during the rapid relaxation phase of the isometric contraction and the relaxation-time curve remained statistically unaltered as well. However, considerable decreases (p less than 0.05-0.001) occurred both in the neural activation and in the force production in the early phases of the rapid isometric contraction during the course of the one-week period. After one full day of rest only slight and statistically nonsignificant changes took place in the mean values of the neuromuscular performance variables examined. The present findings indicate that the high overall daily volume of heavy resistance strength training stimuli may have a considerable role in leading to temporary worsening specifically in the rapid neural activation and correspondingly in rapid force production of the neuromuscular performance capacity even during a very short training period. In athletic training the volume of these types of training stimuli should therefore be carefully considered and matched with the specific purpose of the training season and with the specific requirements of various athletic activities.

Adult↗
PubMed1990

Learning-induced change in neural activity during acquisition and consolidation of a passive avoidance response in the rat.

Time-dependent alterations in neural activity have been established during the acquisition and consolidation of a stepdown passive avoidance paradigm. Change in neural activity was established by administering a glucose analogue, [3H]2-deoxyglucose, 50min prior to sacrifice and estimating perchloric acid soluble counts in nine hand dissected brain regions. Change in [3H]2-deoxyglucose uptake was closely paralleled in both trained and yoked animals for up to 40min following task acquisition however the striatum was the only area to exhibit a task-specific increase in [3H]2-deoxyglucose uptake at 20-30min after training. Longterm changes in neural activity were also apparent as the amygdala and brainstem showed increased [3H]2-deoxyglucose uptake at the 24 h time point. No further paradigm-specific changes were apparent at 48 h. These findings are concluded to suggest that the striatum is involved in the early events of acquiring a passive avoidance response and the amygdala and brainstem during the later events.

Amygdala↗
PubMed1988

Identification and characterization of neurons initiating patterned neural activity in the buccal ganglia of Aplysia.

Two patterns of neural activity were identified in excised buccal ganglia of Aplysia californica. Both are expressed in many cells, and each can be expressed independently. Using cells B4 and B5 as monitors of the activity patterns, we searched the buccal ganglia for cells initiating the patterns. Two electrically coupled cells, B31 and B32, can initiate what we termed pattern 2. The cells are active before pattern 2 is expressed. Stimuli initiating pattern 2 excite B31/B32. Depolarizing B31/B32 induces the pattern, while hyperpolarizing them can prevent its expression. The cells have unusual features. Their somata do not sustain conventional action potentials, and depolarization causes a regenerative response. B33 differs from B31/B32 in that its soma sustains conventional action potentials but otherwise has similar features. B34 also seems to be inexcitable but has weaker synaptic input than B31/B32 and appears unable to induce pattern 2. B35 and B36 have prominent regenerative capabilities. B35 is also able to initiate pattern 2. B37 is presynaptic to B31/B32 and can initiate pattern 2 via its effects on them. The newly identified cells provide a starting point for investigating factors that initiate and control different patterns of neural activity in the buccal ganglia. Since the buccal ganglia are involved in generating feeding behavior, further studies on the newly identified cells may provide insights into the neural control of feeding behavior, and provide a neural substrate for studying modulation of the feeding patterns by associative learning.

Animals↗
PubMed2024

Shared differential factors underlying individual spontaneous neural activity abnormalities in major depressive disorder.

BACKGROUND: In contemporary neuroimaging studies, it has been observed that patients with major depressive disorder (MDD) exhibit aberrant spontaneous neural activity, commonly quantified through the amplitude of low-frequency fluctuations (ALFF). However, the substantial individual heterogeneity among patients poses a challenge to reaching a unified conclusion. METHODS: To address this variability, our study adopts a novel framework to parse individualized ALFF abnormalities. We hypothesize that individualized ALFF abnormalities can be portrayed as a unique linear combination of shared differential factors. Our study involved two large multi-center datasets, comprising 2424 patients with MDD and 2183 healthy controls. In patients, individualized ALFF abnormalities were derived through normative modeling and further deconstructed into differential factors using non-negative matrix factorization. RESULTS: Two positive and two negative factors were identified. These factors were closely linked to clinical characteristics and explained group-level ALFF abnormalities in the two datasets. Moreover, these factors exhibited distinct associations with the distribution of neurotransmitter receptors/transporters, transcriptional profiles of inflammation-related genes, and connectome-informed epicenters, underscoring their neurobiological relevance. Additionally, factor compositions facilitated the identification of four distinct depressive subtypes, each characterized by unique abnormal ALFF patterns and clinical features. Importantly, these findings were successfully replicated in another dataset with different acquisition equipment, protocols, preprocessing strategies, and medication statuses, validating their robustness and generalizability. CONCLUSIONS: This research identifies shared differential factors underlying individual spontaneous neural activity abnormalities in MDD and contributes novel insights into the heterogeneity of spontaneous neural activity abnormalities in MDD.

Humans↗
PubMed1976

Central vestibular compensation. Effect of the bilateral labyrinthectomy on neural activity in the medial vestibular nucleus.

An attempt was made to reconstruct the central events that occurred in the various stages of vestibular compensation after a bilateral labyrinthectomy in the cat. Bilateral labyrinthectomized cats showed no nystagmus, but had unsteady head movements and wide gaits. Neural activity in both sides of the medial vestibular nuclei (MVN) was depressed during the critical stage of compensation; however, the neural activity was full and normal during the acute and compensated stage. The experimental results suggest that removing crossed inhibitory influence and reducing the cerebellar inhibitory influence by bilateral labyrinthectomy enhances the process of recovering neural activity in the vestibular nuclei during central compensation, and that the contralateral vestibular end organ is not a source of the driving force responsible for regeneration of electrical activity in the deafferented MVN after a unilateral labyrinthectomy.

Animals↗
PubMed1976

The effects of neurally active amino acids on prolactin secretion.

Several neurally active amino acids were injected into the third ventricle of anesthetized male rats. Two or eight mumole of GABA produced significant increases in the plasma concentrations of prolactin (PRL), indicating increased PRL release from the pituitary. Two mumole of glycine was also effective in elevating PRL levels. The intraventricular injection of the lowest dose of GABA (1.0 mumole), glutamate (0.4 or 2.3 mumole), lysine (0.2 or 2.0 mumole), or 0.9% NaCl did not alter PRL levels significantly. Plasma PRL concentrations did not increase following the injection of GABA or glycine directly into the anterior pituitary gland. The results suggest that GABA and glycine may play a role in the neural regulation of PRL secretion.

Amino Acids↗
PubMed1989

Influence of muscle mass on sympathetic neural activation during isometric exercise.

The primary purpose of this study was to determine whether the sympathetic neural activation induced by isometric exercise is influenced by the size of the contracting muscle mass. To address this, in nine healthy subjects (aged 19-27 yr) we measured heart rate, systolic arterial blood pressure, and muscle sympathetic nerve activity in the leg (MSNA; peroneal nerve) before (control) and during 2.5 min of isometric handgrip exercise (30% of maximal voluntary force). Exercise was performed with the right and left arms separately and with both arms simultaneously (random order). During exercise, heart rate, systolic pressure, and MSNA increased above control under all conditions (P less than 0.05). For each variable, the magnitudes of the increases from control to the end of exercise were significantly greater when exercise was performed with two arms compared with either arm alone (P less than 0.05). In general, the increases in heart rate, systolic pressure, and MSNA elicited during two-arm exercise were significantly less than the simple sums of the responses evoked during exercise of each arm separately. These findings indicate that the magnitude of the sympathetic neural activation evoked during isometric exercise in humans is determined in part by the size of the active muscle mass. In addition, our results suggest that the sympathetic cardiovascular adjustments elicited during exercise of separate limbs are not simply additive but instead exhibit an inhibitory interaction (i.e., neural occlusion).

Adult↗
PubMed1989

The organization of spatial coding in the hippocampus: a study of neural ensemble activity.

Neural activity was recorded from local groups of hippocampal single units in rats performing a spatial-memory task. The organization of functional correlates in these neural ensembles was investigated by examining the spatial relationships among the place fields of single units in each ensemble. The distance and overlap between place fields were determined together with the tuning of cellular activity to behavioral variables, including direction, speed, and turning angle during movements within place fields. The place fields of recorded neural ensembles were significantly clustered: closer in space and considerably more overlapped than chance when compared statistically with Monte Carlo simulations. Just as single units often have significant firing in more than one distinct location in the environment (subfields), the ensembles had multiple and distinct clusters of overlapping subfields. In addition, proximity and overlap between place fields were significantly, but weakly, correlated with similarity in optimal movement tuning parameters. These results suggest that the hippocampus maintains a local organization with respect to place fields despite having no apparent large-scale isomorphism with the spatial environment. The organization of multiple, clustered place fields with correlated movement tuning properties in small neural ensembles suggests the existence of functional neural ensembles serving to encode multiple sensory and behavioral aspects of a place or event. Such an organization is similar to that observed for neocortical association areas afferent to the hippocampal system.

Animals↗
PubMed1989

Gustatory-salivary reflex: neural activity of sympathetic and parasympathetic fibers innervating the submandibular gland of the hamster.

Electrophysiological experiments were performed to clarify the neural control mechanisms subserving gustatory-salivary reflex in anesthetized and decerebrate hamsters. Efferent neural activities of postganglionic sympathetic and preganglionic parasympathetic fibers, innervating the submandibular gland, were recorded when taste stimuli were infused into the oral cavity. Neural activities of primary gustatory afferents were also recorded from the chorda tympani (innervating the anterior part of the tongue) and the glossopharyngeal nerve (innervating the posterior part of the tongue). The parasympathetic fibers showed a low rate of spontaneous discharges (about 0.3 Hz), and responded tonically in an excitatory manner to taste stimulation. The magnitude of parasympathetic activity was highly correlated with the magnitude of gustatory afferent responses of the chorda tympani rather than that of the glossopharyngeal nerve. On the other hand, the sympathetic fibers showed irregular burst discharges (1.5 burst/s), and the rate of burst discharges was increased in response to high concentrations of HCl (0.03 M) or NaCl (1 M) solutions. Deafferentation experiments suggest that the parasympathetic activity is mainly influenced by gustatory information via the chorda tympani, while the sympathetic activity can be evoked by both the chorda tympani and glossopharyngeal nerve.

Action Potentials↗
PubMed1991

Effect of ketone body (D-3-hydroxybutyrate) on neural activity and energy metabolism in hippocampal slices of the adult guinea pig.

The role of ketone body on neural activity and energy metabolism in the brain was investigated. Guinea pig hippocampal slices were prepared, and postsynaptic field potentials (PSPs) were recorded in the granular cell layer of the dentate gyrus. ATP and phosphocreatine (CrP) in the tissue slice were measured after 60 and 120 min incubation in standard medium (1) with 10 mM glucose, (2) with 10 mM glucose plus 20 mM D,L-3-hydroxybutyrate (3-OHBA), (3) without glucose, (4) with 20 mM 3-OHBA instead of 10 mM glucose. In (3), both ATP and CrP in the slice decreased to 40-45% of the original level after 120 min. On the other hand, the ATP level was well maintained even 120 min after incubation in (1), (2) and (4), whereas the CrP level decreased to 62% in (4). Further, slices were incubated in (3) and (4) for 30, 60, and 120 min, and the presence of PSP was tested. In (3), the number of slices from which PSPs could be recorded decreased, and after 120 min PSPs were hardly observed. In (4), that number decreased gradually, and only 45% of the slices showed PSPs after 120 min. These results indicate that 3-OHBA can be a substrate to produce high-energy phosphate but cannot maintain the neural activity as glucose does.

3-Hydroxybutyric Acid↗
PubMed1990

Discharge of vagal pulmonary receptors differentially alters neural activities during various stages of expiration in the cat.

1. The purpose was to evaluate the hypothesis that neural expiration is composed of two phases: I, a post inspiratory period; and II, the period at which expiratory activities of spinal nerves reach peak values. We hypothesized that the discharge of pulmonary stretch receptors might differentially alter neural activities during these two phases. 2. Activities of the phrenic nerve, intercostal nerve and nerves innervating the thyroarytenoid muscle of the larynx and triangularis sterni muscle of the chest wall were recorded in decerebrate and paralysed cats. 3. The experimental animals were ventilated with a servo-respirator which produced changes in tracheal pressure, and lung volume, in parallel with alterations in integrated activity of the phrenic nerve. 4. In order to assess the influence of the discharge of slowly adapting pulmonary stretch receptors upon neural activities during expiration, lung volume was held at end-expiratory or end-inspiratory levels for individual respiratory cycles. 5. When pulmonary inflation was prevented, phrenic activity increased, as did activity of the thyroarytenoid nerve during early expiration. In contrast, activities of the triangularis sterni and intercostal nerves during mid- to late expiration declined. 6. Holding the lungs at end-inspiratory levels caused a reduction of thyroarytenoid activity and increases in peak triangularis sterni and intercostal activities. Neural expiration typically continued as long as the lungs were maintained at the end-inspiratory level. 7. Responses were qualitatively similar in hypocapnia, normocapnia and hypercapnia, but the magnitude of changes in neural activities was typically augmented with elevations in end-tidal fractional concentrations of CO2. 8. We conclude that the discharge of slowly adapting pulmonary stretch receptors inhibits neural activities during early expiration and augments activities during mid-to late expiration. Hence, our data support the concept that neural expiration is composed of two stages in which neural activities may be differentially controlled.

Animals↗
PubMed1990

A circadian rhythm in neural activity can be recorded from the central nervous system of the cockroach.

Evidence presented in this paper indicates that a robust circadian rhythm in the frequency of neural activity can be recorded from the central nervous system of intact cockroaches, Leucophaea maderae. This rhythmicity was abolished by optic lobe removal. Spontaneous neural activity was then used as an assay to demonstrate that the optic lobe is able to generate circadian oscillations in vitro. These results provide direct evidence that the cockroach optic lobe is a self-sustained circadian oscillator capable of generating daily rhythms in the absence of neural or hormonal communications with the rest of the organism.

Action Potentials↗
PubMed1986

Effects of methylprednisolone on cortical neural activity, blood flow, and water content in air exposure-induced cerebral edema.

The correlation of changes in cortical neuron activity with water content and local cerebral blood flow was investigated in cats with brain edema produced by air exposure. The further effect of high-dose methylprednisolone on these factors was studied. Six hours after exposure of the brain surface to air, the water content of the white matter significantly increased. The local blood flow of the cortex and white matter significantly decreased with significant suppression of cortical neural activity (direct cortical response), indicating that ischemia was responsible for neural suppression. A single, large dose of methylprednisolone (30 mg/kg, i.v.) at the beginning of air exposure significantly reduced brain edema of the cortex and white matter 12 h after air exposure and improved the local blood flow of the cortex. Methylprednisolone also caused a remarkable improvement in cortical neural activity. This steroid effect on cortical neural function may play a role in the rapid neurologic improvement observed with their use in addition to the effect on brain edema.

Air↗
PubMed1989

Differing control of neural activities during various portions of expiration in the cat.

1. Activities of the phrenic nerve, intercostal nerve and nerves innervating the thyroarytenoid (TA) muscle of the larynx and triangularis sterni (TS) muscle of the chest wall were recorded in decerebrate, vagotomized, paralysed and ventilated cats. 2. Neural inspiration was defined by the phase of phrenic activity. Neural expiration was divided into two phases with phase I corresponding to the duration of TA activity and phase II to TS activity: intercostal nerves discharged across both phases. 3. Phrenic activity was terminated prematurely by electrical stimulation of the superior laryngeal nerve or of the dorsolateral region of the rostral pons. Following stimulation, neural activities during phase I of expiration rose and those during phase II fell in most animals. 4. Stimulation of the superior laryngeal nerve during phase I caused augmentations of both TA and TS activity. At the termination of stimulation, a phase of TA discharge was recorded followed by a phase of TS activity. The durations of these post-stimulation phases of TA and TS activities approximated those of cycles without stimulation. 5. Stimulation of the superior laryngeal nerve during phase II caused a resetting of neural expiration. Following stimulation, phases of TA and TS activity were recorded which had durations approximating those of cycles without stimulation. 6. The current required to induce a premature onset of phrenic activity by stimulation of the dorsolateral region of the rostral pons fell dramatically with the change from phase I to phase II of expiration. 7. We conclude that the control of neural activities differs markedly between phase I and phase II of expiration. The data support the hypothesis that post-inspiratory medullary respiratory neurones play a fundamental role in the definition of the ventilatory cycle.

Animals↗
PubMed1979

Entrainment of oscillatory neural activity in the cat's lateral geniculate nucleus.

Oscillatory neural activity in the frequency range 7-12 Hz is observed in the lateral geniculate nucleus (LGN) of the lightly anesthetized cat. This paper describes a series of experiments in which the interactions between ongoing oscillatory potentials and periodic photic and electrical stimuli are analyzed using frequency domain techniques. The principal results of these experiments are consistent with a model of the neural system as an entrainable oscillator in which ongoing oscillations are suppressed by stimulation at nearby frequencies, but coexist with stimulus frequencies farther away. The physiological interpretation of these results may be closely tied to the role of the LGN as a "gating" mechanism between retina and cortex.

Alpha Rhythm↗