SEARCH · Search PubMed

Results for “Spontaneous activity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1979

Effects of baroreceptor activation on spontaneous activity in the sweat glands and nictitating membrane of the cat.

(1) In chloralose-anesthetized cats, elevation of carotid sinus pressure caused blood pressure, sweat gland potentials and nictitating membrane tension to decrease. (2) The onset and recovery of the sweat gland and nictitating membrane responses usually preceded the respective phases of the blood pressure (depressor) response; the latencies of the sweat gland and nictitating membrane responses agreed with the latencies predicted for neural reflex pathways. (3) The sweat gland and nictitating membrane responses were evoked less consistently than the depressor response. (4) In experiments where only the sweat gland potentials and blood pressure were studied: (a) the sinus pressure threshold for inhibition of sweat gland activity was similar to the threshold for the depressor response; (b) cutting the sinus nerves, or blocking the efferent neural activity to the sweat glands, eliminated the effects of sinus pressure elevation on the sweat gland potentials; (c) with carotid sinus pressure held constant, decreases in blood pressure, produced by stimulating the peripheral end of the vagus nerve, did not affect the sweat gland potentials. (5) These results indicate that baroreceptors can reflexly modulate activity in sympathetic neurons whose target organs are not fundamentally involved in blood pressure regulation.

Adrenergic Fibers↗

PubMed1992

An improved graphical method for pattern recognition from spike trains of spontaneously active neurons.

Spontaneous activity and rhythmical oscillations are common features of large neuronal networks in mammals. Detection of repetitive spike patterns or pacemaker activity during electrophysiological recording of spontaneous action potentials from single neurons can be difficult if a "noisy" background is present. This paper describes an improved method for an online spike train analysis based on joint interval histograms (JIH, Rodiek et al. 1962). By means of higher ordered JIH the discrimination of spike patterns with repetitive bursting activity or oscillations is possible even when randomly distributed action potentials appear. Examples of simulated spike trains and those recorded from cultured hippocampal neurons are presented.

Animals↗

PubMed1978

Spontaneous activities of female versus male newborns.

This study explored potential sex differences in all activity spontaneously emitted by newborns. 2 groups of full-term infants (14 uncircumcised males, 15 females), equally distributed along several physical and demographic variables, served as subjects. Each newborn was observed for a total of 8 hours during the 2 days following birth. Observational procedures were stringently controlled and interobserver reliability ranged from .84 to .98. Results showed higher levels of wakefulness, facial grimacing, and low-intensity motor activity for males. Of marginal significance, both low-intensity and high-intensity oral activity was higher for males. In addition, a marginally significant interaction effect (sex X interfeeding interval X day) was found for high-intensity oral activity (crying). Independent of sex, high-intensity activity increased in the evening and over an interfeeding period, and low-intensity oral activity increased over days. The pattern of results indicates that even uncircumcised males may be slightly more irritable than females, and thus more active. Potential implications of these findings are considered.

Circadian Rhythm↗

PubMed1976

Spontaneous activity in denervated mouse diaphragm muscle.

Intracellular electrodes were used to study the discrete depolarizations which trigger fibrillation potentials in chronically denervated mouse diaphragm muscles. Provided that the muscles were perfused on both sides spontaneous activity was maintained in vitro. 2. Discrete spontaneous depolarizations, present only in the centre of the muscle, were recorded from the third day of denervation reaching a maximum in prevalence 9-12 days after sectioning the nerve. These potentials had random occurrence and nearly constant amplitude and frequency within a fibre, dependence of amplitude and frequency on membrane potential, and low temperature dependence. 3. The spontaneous activity was enhanced and could be initiated in previously quiescent fibres by lowering the external Ca concentration. The activity was reduced by increasing external Ca and was abolished at 15mM-[Ca] 0. Tetrodotoxin (10-(7)M) blocked spontaneous activity. 4. The spontaneous activity was enhanced by the catecholamines isoprenaline and adrenaline (0.5-10 mug/ml.). This effect of isoprenaline was accompanied by an increase in the rate of rise and the amount of overshoot of the action potential. 5. Ouabain (10-(6)-10-(4)M) of K+-free solutions reversibly blocked spontaneous activity. Ouabain (10-(4)M) reduced the rate of rise and the amount of overshoot of the action potential. 6. Detubulation of muscle fibres with glycerol of the presence of hypertonic solutions abolished spontaneous activity which could not be restarted by reducing Ca or by the addition of isoprenaline. 7. The results support the suggestion that the spontaneous discrete depolarizations which give rise to fibrillation potentials in denervated muscle result from regenerative sodium conductance increases within the transverse tubular system of the muscle fibres. Catecholamines and ouabain could affect this activity either directly, through an action on membrane excitability, or indirectly via the Na+-K+ pump.

Action Potentials↗

PubMed1976

Ba2+ and K+ alteration of K+ conductance in spontaneously active vascular muscle.

The spontaneous spiking of vascular muscle in hepatic portal vein was converted from a burst pattern to single spiking by K+ concentrations greater than 20 mM. A pronounced decrease in contraction amplitude was always associated with the conversion of bursts of spikes to single spikes. The single spikes were accompanied by contractions that were only 1-5% of the magnitude of the contractions associated with spike bursts. Ba2+ (1 mM) increased the number of spikes per burst in myovascular cells at low(less than 10 mM) K+ concentrations. Even though Ba2+ caused depolarization, which itself tended to cause conversion to single spiking, the number of spikes per burst and contraction amplitude were greater in Ba2+ solutions. The slope of the Em-log [K+]o relationship depended on the time allowed for changes in [K+], and a maximum slope of 36 mV/decade and an extrapolated [K+]i of 160 mM were the highest slope and lowest [K+]i values recorded. Ba2+ slightly decreased (to 28 mV/decade) the slope of the curve but did not alter the intercept at [K+] = 160 mM. Ba2+ caused an increase in input resistance (rin) and depolarization independent of CL- concentration, and thus appeared to decrease K+ conductance. K+ concentration increases tended to increase K+ conductance (decrease rin) with depolarization. Spontaneously active vascular muscle thus appears to have a K+ conductance that can be altered and to show different spike patterns and altered conduction, resulting in a marked change in contractions. The spike pattern appears to depend at least partially on the combination of K+ conductance and Em.

Animals↗

PubMed1978

The effect of indomethacin on spontaneous activity in the isolated human myometrium and on the response to oxytocin and prostaglandin.

The spontaneous activity of human myometrial strips obtained during the proliferative and secretory phases of the menstrual cycle and during the early and late stages of pregnancy was studied. Both prostaglandin F2alpha (PGF2alpha) and oxytocin caused contractions which were superimposed on a low level of spontaneous activity but only PGF2alpha was seen to affect high levels of activity. Spontaneous contractions were ultimately abolished by the addition of indomethacin. The strips remained responsive to PGF2alpha but not to oxytocin.

Drug Interactions↗

PubMed1977

The influence of adenylate cyclase inhibitors on the spontaneous activity of the cardiac pacemaker.

The effects of adenylate cyclase inhibitors, haloperidol and chlorpromazine, on the spontaneous activity of the rabbit sinus node was studied by means of double sucrose gap and intracellular microelectrodes. Haloperidol and chlorpromazine arrested the spontaneous activity which could be restored with noradrenaline, in the presence of haloperidol, or with dibutyryl c AMP, in the presence of either inhibitor used. After arresting of the spontaneous activity, sinus node cells might utilize metabolic energy supplied from exogenous pyruvate. Pyruvate protected from depolarization or reestablished polarization in depolarized cells but was not able to restore the spontaneous activity. Discussion of these results suggests that c AMP may be directly involved in the spontaneous electrogenesis in the sinus node.

Adenylyl Cyclase Inhibitors↗

PubMed1977

The effects of indomethacin on the tone and spontaneous activity of the human small intestine in vitro.

The effects of indomethacin on the tone and spontaneous activity of muscle strips from the human terminal ileum were studied. On the longitudinal muscle layer indomethacin caused a loss of tone and a decrease in spontaneous activity. If the drug was added at the beginning of the experiment then the characteristic increase in tone was not observed. On the circular muscle layer indomethacin either initiated or markedly increased spontaneous activity of the muscle strips. Evidence from the in vitro experiments suggests that prostaglandins may be involved in the maintenance of tone of longitudinal muscle and suppression of spontaneous activity in circular muscle from the human terminal ileum.

Gastrointestinal Motility↗

PubMedDate not supplied

[Effects of reversing the feeding cycle and the light period on the spontaneous activity of the rat (author's transl)].

The amount and the circadian distribution of spontaneous activity in the rat are influenced by a number of factors, whose importance and interrelationships are still deeply discussed. In order to check the reliability of previous studies about the effects of meal-eating on the spontaneous activity (wheel running) of rats of our Sprague-Dawley strain, the adjustment to the modifications of the normal day-night cycle and of the normal nocturnal feeding rhythm have been controlled. Reversing the normal light and dark periods caused the rats, after a 24 hours period, to lower and to irregularly distribute their spontaneous activity. Rats shifted their pattern of maximal activity by 12 hours in the new period of darkness in about five days, and showed to have completely fixed the new reversed running habit. Also feeding habits changed in a similar way, but more slowly. The levels of mean daily activity did not change. In a second experiment, rats, received food during light hours, and were deprived during dark hours. Their activity increased considerably and irregularly during dark hours, while a very slight rise of wheel running was shown during light hours. Body weight gain and food consumption were similar to those of the control group. These results slightly differ from those obtained using other rat strains, and are an interesting example of reinforcement of a spontaneous behavior resulting more from the light-dark cycle than from cues provided by food deprivation.

Animals↗

PubMed1977

Actions of atmospheric ionization on spontaneous activity of an amphibian larva.

In Pleurodeles waltlii (Urodela) larvae, spontaneous activity and the tendency to leave water are significantly influenced by artificial air ionization. Atmospheric ions of negative and positive polarities have opposite effects: the latter reduce spontaneous activity by 48% whereas negative ions increase it by 39%. This difference must be considered the result of a specific behavioral effect rather than attributable to the stage of development of the larvae. A comparison of our results with data in the literature indicates that the action of the air ions on amphibian activity may involve the modulation of serotonin and prolactin releases.

Air Ionization↗

PubMed1992

The effects of prenatal cocaine exposure on spontaneously active midbrain dopamine neurons in adult male offspring: an electrophysiological study.

In this study, the technique of extracellular single unit recording was used to examine the effect of prenatal cocaine exposure on the number of spontaneously active dopamine (DA) cells in the substantia nigra pars compacta (SNC or A9) and the ventral tegmental area (VTA or A10) of male Sprague-Dawley rats on postnatal days 56-68. In addition, the effect of the direct DA receptor agonist (+/-)-apomorphine (APO) on the basal firing rate of A10 DA cells was also determined. A significant decrease in the number of spontaneously active A10 DA cells was observed in offspring whose dams were treated with 40 mg/kg/day of cocaine s.c. from gestational days 8-20 when compared with offspring of pair-fed and non-treated control dams. The number of spontaneously active A9 DA cells was significantly decreased in the offspring of cocaine-exposed dams when compared to pair-fed offspring. In contrast, there were no significant differences among the three prenatal groups regarding the sensitivity of spontaneously active A10 DA cells to APO (2-64 micrograms/kg, i.v.). Overall, our results suggest that in utero cocaine exposure may alter presynaptic DA activity in offspring long after their exposure has been terminated.

Animals↗

PubMed1979

Effects of morphine on spontaneous activity of 18-day rat fetus.

The effects of morphine on spontaneous activity of 18-day fetal rats have been observed in utero. Morphine injected subcutaneously in the dam caused a decrease in fetal spontaneous activity which was dose-dependent. The maximum depression of activity occurred after 20 mg/kg was administered to the dam. Activity returned to control levels following naloxone administration to the dam. Fetuses which had been chronically exposed to morphine from days 7 through 17 and observed on day 18 of gestation became hyperactive following administration of naloxone to the dam. This is thought to represent fetal withdrawal.

Animals↗

PubMed1977

Comparison of spontaneous activity of mesencephalic reticular neurones in the waking state and during pentobarbital anaesthesia.

In rats immobilized by d-Tubocurarine the spontaneous activity of 100 mesencephalic reticular neurones was recorded extracellularly and statistically evaluated before and after repeated intravenous administration of 15 mg/kg doses of Pentobarbital. Number of spontaneously active neurones decreases quasi-linearly with repeated 15 mg/kg Pentobarbital doses. After a 75 mg/kg cumulative dose practically all neurones ceased firing spontaneously, whereas cortical EEG activity fully disappeared after the 90 mg/kg Pentobarbital dose. The firing rate was characterized by the mean interval with its standard deviation. Mean value for the total sample of spontaneously active neurones was 146.7 +/- 192.3 msec without Pentobarbital and increased to 302.7 +/- 367.5 msec after 15 mg/kg and to 400.6 +/- 452.5 msec after 30 mg/kg cumulative dose of Pentobarbital. The 15 mg/kg dose increased the frequency of firing in 5% of neurones only. The most often encountered type of interval histogram in the mesencephalic reticular formation was the exponential type (59% in unanaesthetized state), which was also most sensitive to Pentobarbital. Synchronized activity in bursts, characterized by periodical peaks and dips frequently occurred in neurones with the exponential-like interspike interval density after Pentobarbital administration. On the contrary, neurones with gamma-like and especially with symmetrical-like types of density were less influenced by Pentobarbital. In many neurones a periodical increase in the firing rate (with intervals of tens of seconds) related to the occurrence of spindles was present in the cortical EEG activity.

Action Potentials↗

PubMed1975

Ionic determinants of spontaneous activity in clusters of cultured cardiac cells from newborn rats.

The spontaneous activity of cell clusters derived from ventricle cells of newborn rats was studied using a recording television microscope. The influence of varying concentrations of sodium, potassium, calcium, tetrodotoxin (TTX), and that of 2 mM MnCl2 was tested. The spontaneous activity of the cell clusters persisted in TTX but it was abolished by Mn. The beating rate increased when [Ca]0 and [Na]0 were changed from 0.3 mM to 3.0 mM and from 30 mM to 75 mM; it decreased with a change of [Na]0 from 75 mM to 142 mM. It is concluded that electrogenesis in their behavior to very young embryonic rat heart cells or cells of the rabbit sinoauricular node.

Animals↗

PubMed1992

Spontaneous activity of the light-dependent channel irreversibly induced in excised patches from Limulus ventral photoreceptors.

We have studied the properties of membrane patches excised from the transducing lobe of Limulus ventral photoreceptors. If patches are excised into an "internal" solution that resembles the ionic composition of the cytoplasm, channel activity is typically absent, but can be turned on by cyclic GMP (cGMP). In contrast, if patches are excised directly into sea water and subsequently examined in internal solution, they exhibit a high channel activity in the absence of any second messenger (spontaneous channel activity). Because these patches contained only light-dependent channels when examined before excision and because these spontaneous channels have properties in common with the light/cGMP-dependent channel, we believe that the spontaneously active channels represent light/cGMP-dependent channels that have been damaged by exposure to sea water, perhaps due to proteolysis activated by the high Ca2+ levels of the sea water. One type of the spontaneously active channel resembles the light/cGMP-dependent channel in open time, reversal potential, conductance states and voltage dependence. Application of micromolar Ca2+ to this channel produces a reversible decrease in the opening rate, indicating a high affinity binding site for Ca2+ on this channel. Another type of spontaneously active channel has a conductance state and reversal potential similar to the light/cGMP-dependent channel, but has apparently lost its dependence and sensitivity to Ca2+ and voltage.

Animals↗

PubMed1976

Analysis of spontaneous activity of auditory neurones in the spiral ganglion of the guinea-pig cochlea.

1. Spontaneous activity of single afferent neurones in the cochlea of the guinea-pig was studied by measurement of mean rates and computation of interspike interval histograms. 2. The shapes of interval histograms agreed with those found in cat cochlear nerve fibres. Modes of the histograms were less than 7 msec for all cells with mean rates ranging from 20 to 150 spikes/sec. 3. The distribution of mean rates showed higher maximum rates than those found in cat. Cells from animals with abnormally high thresholds showed lower mean rates than those from sensitive animals. 4. No correlation was found between mean spontaneous rate and sensitivity to acoustic stimulation. No discrete populations of cells could be discerned on any of the criteria used. 5. The simultaneous effects of hypoxia on cell thresholds, mean spontaneous rate and scala media potentials are reported. These and other results are discussed in relation to possible sites of generation of spontaneous activity in primary auditory afferents.

Action Potentials↗

PubMedDate not supplied

Long lasting changes in the spontaneous activity of hippocampal neurons following stimulation of the entorhinal cortex.

The spontaneous activity of hippocampal and denate units was investigated in acute and chronic experiments on adult rats. Spontaneous unitary discharges from both regions were measured before and after brief tetanic stimulation of the entorhinal cortex. An increase in the frequency of spontaneous unit activity was obtained in units recorded from the dentate gyrus and CA3 field of the hippocampus for up to 20 min following stimulation. In chronic recordings of physiologically identified dentate units from freely moving rats similar results were obtained. The findings are discussed with reference to long lasting potentiation of synaptic activity in the perforant path-dentate granule cell connection.

Action Potentials↗

PubMed1992

Chronic treatment with DAU 6215, a new 5-HT3 receptor antagonist, causes a selective decrease in the number of spontaneously active dopaminergic neurons in the rat ventral tegmental area.

Electrophysiological techniques were used to study the effects of the new compound, DAU 6215 ((3-alpha-tropanyl) 1H-benzimidazolone-3-carboxamide chloride), a selective 5-HT3 receptor antagonist, on the activity of dopamine (DA)-containing neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA). Acute i.v. injections of DAU 6215 did not cause any change in the basal firing rate of DA neurons in the SNc or in the VTA. Pretreatment with DAU 6215 did not modify the inhibitory effect of apomorphine on the firing rate of midbrain DA neurons. Acute s.c. administration of DAU 6215 caused a significant increase in the number of spontaneously active DA neurons in the VTA but not in the SNc. This effect was similar to that of acute clozapine, whereas acute haloperidol caused a significant increase of spontaneously active DA neurons in both the SNc and the VTA. Repeated consecutive s.c. administration of DAU 6215 and clozapine for 21 days produced a significant decrease in the number of spontaneously active DA neurons in the VTA but not in the SNc. Chronic haloperidol (21 days) decreased the number of DA cells both in the SNc and VTA. The effect of chronic DAU 6215 on the activity of VTA DA neurons was reversed by apomorphine, suggesting that these neurons were probably under a state of depolarization block. These findings indicate that DAU 6215 may have potential antipsychotic activity, probably associated with a low incidence of extrapyramidal side-effects.

Animals↗