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PubMedDate not supplied

[Lateral hypothalamus stimulation as a conditioned stimulus for an alimentary instrumental reflex].

Dynamics of the behavioral effects of LH-stimulation which was used as a conditioned stimulus of alimentary reflex, was recorded in dogs during reflex elaboration, extinction and restoration. Before the elaboration, LH-stimulation elicited either an alimentary instrumental relflex, previously established, or a searching, sniffing, licking, orienting reaction, in the majority of cases with variable latencies. Combination of stimulation and achievement of the alimentary instrumental reflex with subsequent reinforcement in short time stabilized the feeding response. Searching, sniffing, orienting reaction disappeared during the elaboration of the conditioned reflex. Elimination of food reinforcement led to extinction of the alimentary reflex to LH-stimulation. In some sessions full abolition of the feeding response was achieved. LH-stimulation inhibitory properties are assumed. The restoration of the alimentary response to LH-stimulation after single reinforcement demonstrated a high plasticity of this structure. The dynamics of the reflex elaboration, extinction and restoration was the same in response both to brain stimulation and to distant stimuli (sound and light). The implicit motivational properties of LH-stimulation were manifested in the ability to activate the feeding behavior in the satiated dogs.

Animals↗

PubMed2002

Short-term reduction of intracortical inhibition in the human motor cortex induced by repetitive transcranial magnetic stimulation.

Ten healthy subjects and two patients who had an electrode implanted into the cervical epidural space underwent repetitive transcranial magnetic stimulation (rTMS; 50 stimuli at 5 Hz at active motor threshold intensity) of the hand motor area. We evaluated intracortical inhibition before and after rTMS. In healthy subjects, we also evaluated threshold and amplitude of motor evoked potentials (MEPs), duration of cortical silent period and short-latency intracortical facilitation. rTMS led to a short-lasting reduction in the amount of intracortical inhibition in control subjects with a high interindividual variability. There was no significant effect on other measures of motor cortex excitability. Direct recordings of descending corticospinal volleys from the patients were consistent with the idea that the effect of rTMS on intracortical inhibition occurred at the cortical level. Since the level of intracortical inhibition can be influenced by drugs that act on GABAergic systems, this may mean that low-intensity repetitive magnetic stimulation at 5 Hz can selectively modify the excitability of GABAergic networks in the human motor cortex.

Adult↗

PubMed1976

Innervation of pelvic viscera in the rat. Evoked potentials in nerves to bladder and penis (clitoris).

In 29 rats, responses evoked by pelvic and hypogastric nerve stimulation were recorded from postganglionic nerves to bladder and penis (clitoris). Responses to pelvic nerve stimulation had nonsynapsing and synapsing components. The nonsynapsing component was relatively large in main nerve to penis and small in lateral nerve to penis and nerves to bladder. Pelvic nerve fiber synapsing on pelvic ganglion neurons to bladder had a large subliminal fringe, while fibers synapsing on neurons supplying penis (clitoris) had a small subliminal fringe. Recruitment was greater in nerves to bladder and lateral nerve to penis (clitoris) compared to main nerve to penis (clitoris), indicating more synapsing fibers in the former nerves. Almost all hypogastric fibers to bladder were direct. A small subliminal fringe was demonstrated for hypogastric fibers synapsing on neurons supplying penis. No subliminal fringe was evident for the bladder. Pelvic and hypogastric nerve interaction on pelvic ganglion neurons could not be demonstrated with either single shock or tetanic trains of conditioning stimuli. With antidromic stimulation, conduction velocities of afferent fibers in pelvic nerve ranged from 0.15 m per sec to 2.9 m per sec. In hypogastric nerve they ranged from 0.35 m per sec to 2.8 m per sec.

Animals↗

PubMed1993

Differences in adaptation between on- and off-centre ganglion cells and rod-mediated cone sensitization in cat retina.

1. Response properties of on- and off-centre retinal ganglion cells were investigated in cats. The stimulus parameters were selected so as to demonstrate interactions between the rod and the cone systems. 2. Response versus log stimulus intensity (R-log I) functions were determined for the receptive field centres while both test stimulus irradiance and the background illumination were varied over a range up to 7 log units. In order to determine the course of adaptation to chromatic stimuli, threshold versus intensity (t.v.i.) functions were measured over a wide range of adaptation levels. 3. An increase in background illuminance produced a shift of the R-log I functions to higher irradiances of test stimuli in most ganglion cells, indicating a desensitization of the centre response in the presence of background lights. Using test stimuli which most efficiently stimulate the rods (501 nm), clear differences could be seen in the adaptation behaviour of on- and off-centre ganglion cells. Chromatic backgrounds (blue-green and orange) reduced the responses of off-centre cells more than those of on-centre cells (the difference between them amounting to as much as 2 log units). Simultaneously, equivalent t.v.i. functions had significantly steeper slopes (0.94 and 1.1) in the linear proportions of off-centre cells compared to on-centre cells (0.76 and 0.75) under light levels mediated by rods. Such differences were not observed when a test stimulus of 575 nm was used which resulted primarily in stimulating the long-wavelength cone (L-cone) system. 4. In a subpopulation of off-centre cells (20% of the total number of off-centre cells recorded), a strikingly different adaptation behaviour was observed. Here, the presentation of a dim short-wavelength background produced a shift of R-log I functions to lower test stimulus irradiances. The receptive field centre became even more sensitive, by up to 1.5 log units, in the presence of dim adapting backgrounds rather than in the dark-adapted state. Accordingly, the t.v.i. function did not increase monotonically but showed a 'dip' in the presence of dim backgrounds. Only at photoic levels, the t.v.i. functions revealed a response behaviour similar to the other ganglion cells. The sensitization with dim backgrounds was only observed in the case of test stimuli designed to stimulate the cone system (575 nm) and in the presence of a rod-adapting blue-green background.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗

PubMed2003

Noxious stimuli do not modify myogenic motor evoked potentials by electrical stimulation during anesthesia with propofol-based anesthesia.

PURPOSE: To investigate whether motor evoked potentials (MEP) to transcranial electrical stimulation under constant blood propofol concentration are affected by the arousing effect of surgical noxious stimuli. METHODS: Twenty patients who underwent elective spinal surgery were studied. Patients were anesthetized with 50% nitrous oxide in oxygen, fentanyl, and propofol to maintain the bispectral index (BIS) score around 50. MEP in response to a multipulse transcranial electrical stimulation at stimulus sites of C3-C4 were recorded over the right abductor pollicis brevis muscle. Changes of peak-to-peak amplitude and onset latency of MEP, BIS score before and after surgical stimuli were evaluated. Propofol plasma concentration was measured at the same time points. RESULTS: Both MEP amplitude and latency did not change significantly after surgical stimuli although BIS increased significantly (48 +/- 6 to 58 +/- 5; P < 0.05). Plasma propofol concentration was maintained at the same level between the two measurement points (3.3 +/- 0.7 to 3.3 +/- 0.7 micro g*mL(-1)). There was no relation between BIS change and changes of MEP amplitude and latency, and propofol plasma concentration. CONCLUSION: MEP to the transcranial electrical stimulation under a constant and clinically appropriate blood propofol concentration are not affected by surgical noxious stimuli.

Anesthesia, General↗

PubMed1997

Taste in chimpanzees II: single chorda tympani fibers.

Data are presented from 48 taste fibers in chorda tympani nerves of 10 chimpanzees during taste stimulation with 29 stimuli. The results demonstrated a higher taste fiber specificity than in any other mammalian species reported; breadth of tuning equals 0.3. Hierarchical cluster analysis separated an S-cluster (50% of all fibers), an N-cluster (31%), and a Q-cluster (19%). The S-cluster showed the highest specificity. Its fibers responded, with few exceptions, to every sweetener tested, including the sweet proteins brazzein and monellin. The response grew with increasing sweetener concentration. A large response to one sweetener was generally accompanied by a large response to all other sweeteners, and vice versa. Except for one broadly tuned fiber, the fibers of the S-cluster never responded to the bitter compounds. The fibers of the Q-cluster were more broadly tuned than any other fibers. Quinine hydrochloride was their best stimulus, but most fibers were also stimulated by KCl and NaCl with amiloride. Acids stimulated some of these fibers. The N-cluster could be divided into 3 subclusters: an Na-subcluster (3 fibers), Na-K subcluster (10 fibers), and M-subcluster (3 fibers). The Na-fibers responded strongly to, and were quite specific to, NaCl and LiCl stimulation but not to KCl, and fibers of the Na-K subcluster responded equally well to NaCl and KCl. The response to NaCl was suppressed by amiloride in the fibers of the Na-subcluster, but not in the fibers of the Na-K subcluster. Umami compounds elicited the strongest responses in the M-subcluster.

Animals↗

PubMed1989

The spontaneous electrical and mechanical activity of human bronchial smooth muscle: its modulation by drugs.

1. Tissue taken at operation was used to study the electrical and mechanical properties of human bronchial smooth muscle with intracellular microelectrodes and isometric recording of tension changes. 2. Over 90% of the muscle strips exhibited spontaneous tone and 70% produced spontaneous phasic contractions. The resting membrane potential of the smooth muscle cells ranged between -40 to -50 mV with a mean value of -44.9 +/- 5.2 mV (n = 92 +/- s.d.). Spontaneous oscillations of the membrane potential (slow waves) were observed in 90% of the cells examined. 3. The electrical slow waves, phasic contractions and spontaneous tone were greatly reduced by FPL 55712 (10(-6)-10(-5) M). Indomethacin (1-5 x 10(-5) M), atropine (10(-6) M) or a 5-lipoxygenase inhibitor, AA 861 (5 x 10(-6) M) each reduced spontaneous mechanical tone. Indomethacin and atropine each caused minor reduction in the amplitude of electrical slow waves. 4. Leukotriene C4 (10(-8) M), physostigmine (10(-6) M) and K+-rich physiological salt-solution (containing atropine 10(-6) M) each caused tone development in tissue treated with AA 861 (5 x 10(-6) M). In the case of leukotriene C4 and physostigmine, phasic contractions were superimposed on the developed tone. 5. Electrical field stimulation evoked an excitatory junction potential (e.j.p.) followed by a small group of slow waves. Repetitive field stimulation (2-20 stimuli at 20 Hz) markedly enhanced the amplitude of oscillatory slow waves. FPL 55712 (1.9 x 10(-6) M) abolished the oscillatory slow waves following the e.j.p., and physostigmine (10(-6) M) enhanced the amplitude of the e.j.p. and slow waves. 6. These results indicate that, under in vitro conditions, the electrical activity of human bronchial smooth muscle comprises slow wave discharge which may be related to the spontaneous contractions and generation of basal tone.

Adult↗

PubMed1982

Comparative effects of electroacupuncture and transcutaneous nerve stimulation on the human blink reflex.

The effects of low frequency (2 Hz) high intensity (10-12 mA) (electroacupuncture, EA) and of high frequency (100 Hz) low intensity (2 mA) (transcutaneous nerve stimulation, TNS) conditioning stimuli were studied on the nociceptive component (R2) of the blink reflex in normal volunteers. EA induced a progressive and moderate partially naloxone-reversible depression in the R2 response. In contrast, TNS induced a rapid and major depression in this reflex. In this latter case, naloxone failed to produce any reversal effect. These two patterns of data are discussed and further electrophysiological studies provide some evidence for two different mechanisms in the depressive effects of EA and TNS upon the nociceptive component of the blink reflex in man.

Acupuncture Therapy↗

PubMed1994

An investigation of depotentiation of long-term potentiation in the CA1 region of the hippocampus.

We have investigated long-term synaptic depression in the CA1 region of rat hippocampal slices. Prolonged low-frequency stimulation (LFS; 900 stimuli delivered at 2 Hz) of the Schaffer collateral-commissural pathway in naïve slices did not induce long-term depression (LTD) of synaptic transmission. However, if long-term potentiation (LTP) was firstly induced in the pathway then LFS generated an LTD-like effect (i.e. depotentiation of LTP). Depotentiation could be induced 2 h (the longest time studied) after the induction of LTP and was stable for the duration of the experiment (followed for up to 40 min). The induction of depotentiation was not blocked by the N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonopentanoate, the L-type voltage-gated Ca2+ channel blocker nimodipine or the nitric oxide synthase inhibitor N omega-nitro-L-arginine. However, the magnitude of depotentiation was reversibly reduced, in a stereoselective manner, by the specific metabotropic glutamate receptor (mGluR) antagonist (+)-alpha-methyl-4-carboxyphenylglycine. These results show that prolonged low frequency stimulation can result in an mGluR-dependent depotentiation of LTP.

2-Amino-5-phosphonovalerate↗

PubMed1991

Temporal integration of electrical stimulation of auditory nuclei in normal-hearing and hearing-impaired cat.

Temporal integration functions were measured, before and after a sound-induced hearing loss, in 5 cats using trains of electrical pulses applied to auditory nuclei in the brainstem. The 8 stimuli ranged from 1 pulse (0.25 ms duration) to 16 pulses (0.25 ms pulses spaced over 240 ms). The stimuli were applied to inferior colliculus or cochlear nucleus via permanently implanted electrodes. One electrode was tested extensively in each animal to obtain 10 sets of behaviorally-measured electrical detection thresholds counterbalanced across stimuli. The animal was then exposed to a 110 dB SPL, 2 kHz tone for 48 h and pre- and post-exposure audiograms were measured. The mean permanent threshold shift for acoustic stimuli was 48.5 dB. Another 10 thresholds for each of the 8 electrical stimuli were then measured. In the normal hearing animals, the mean slope of the temporal integration function for electrical stimulation was -7.6 dB per factor of 10 pulses. Alternatively, the mean time constant was 139 ms. In the hearing impaired animals, the slope was reduced to -1.5 dB per factor of 10 pulses, which corresponded to a mean time constant of 17 ms. In addition, the hearing impaired animals showed a decreased threshold for the electrical stimuli (stimulation hypersensitivity) as well as reduced variability across electrical stimulation thresholds. The results suggest that a major contribution to temporal integration occurs in inferior colliculus or higher. In addition, the results suggest that the reduction in temporal integration that follows hearing impairment is a peripherally-induced, central effect.

Animals↗

PubMed1981

Oligosynaptic excitation of motoneurones by impulses in group Ia muscle spindle afferents in the cat.

1. Intracellular recording from hind-limb motoneurones was used to investigate whether di- and trisynaptic (oligosynaptic) excitatory post-synaptic potentials (e.p.s.p.s) are evoked from group Ia muscle spindle afferents in those motoneurones in which such potentials are evoked from Ib tendon organ afferents or entire group I afferents. Ia afferents of triceps surae and plantaris were activated either selectively by single brief stretches of these muscles, or together with Ib afferents by electrical stimuli applied to the nerves.2. Muscle stretches below threshold for Ib afferents (10-35 mum) evoked e.p.s.p.s which appeared with latencies compatible with disynaptic and trisynaptic coupling between the afferents and the motoneurones. The latencies of a majority of these e.p.s.p.s were too short to allow their mediation by group II afferents, if any were activated by the applied stretches. They were also too short to be compatible with effects attributable to dorsal root reflexes. These e.p.s.p.s are thus attributed to oligosynaptic actions of Ia afferents.3. Stretch-evoked di- and trisynaptic Ia e.p.s.p.s were found in 83% of motoneurones in which e.p.s.p.s were evoked by stimuli which activated both Ia and Ib afferents; in five motoneurone species they were found in more than 90%. These observations lead to the conclusion that group Ia muscle spindle afferents evoke not only inhibitory but also excitatory actions in parallel with group Ib tendon organ afferents.4. The distribution of Ia oligosynaptic stretch-evoked excitation from ankle and toe extensor muscles was compared with the distribution of Ia non-reciprocal inhibition as described by Jankowska, McCrea & Mackel (1981b). Excitation pre-dominated in posterior biceps-semitendinosus motoneurones and inhibition in other species of motoneurones investigated, except those of intrinsic foot muscles (tibial motoneurones); similar proportions of the latter showed excitation and inhibition.5. Occurrence of oligosynaptic e.p.s.p.s as well as inhibitory post-synaptic potentials (i.p.s.p.s) of Ia origin in some motoneurone species, and in particular in individual motoneurones, is indicative of a number of reflex pathways between group I afferents and these motoneurones. Furthermore, the disappearance of some of the e.p.s.p.s evoked by near-threshold electrical stimulation following stronger stimuli indicates interactions between various functional groups of interneurones mediating group I actions.

Animals↗

PubMed2005

Dopaminergic transmission in STOP null mice.

Neuroleptics are thought to exert their anti-psychotic effects by counteracting a hyper-dopaminergic transmission. Here, we have examined the dopaminergic status of STOP (stable tubule only polypeptide) null mice, which lack a microtubule-stabilizing protein and which display neuroleptic-sensitive behavioural disorders. Dopamine transmission was investigated using both behavioural analysis and measurements of dopamine efflux in different conditions. Compared to wild-type mice in basal conditions or following mild stress, STOP null mice showed a hyper-locomotor activity, which was erased by neuroleptic treatment, and an increased locomotor reactivity to amphetamine. Such a behavioural profile is indicative of an increased dopaminergic transmission. In STOP null mice, the basal dopamine concentrations, measured by quantitative microdialysis, were normal in both the nucleus accumbens and the striatum. When measured by electrochemical techniques, the dopamine efflux evoked by electrical stimulations mimicking physiological stimuli was dramatically increased in the nucleus accumbens of STOP null mice, apparently due to an increased dopamine release, whereas dopaminergic uptake and auto-inhibition mechanisms were normal. In contrast, dopamine effluxes were slightly diminished in the striatum. Together with previous results, the present study indicates the association in STOP null mice of hippocampal hypo-glutamatergy and of limbic hyper-dopaminergy. Such neurotransmission defects are thought to be central to mental diseases such as schizophrenia.

Action Potentials↗

PubMed1977

A second order model of the optic generator potential and its relation to Stevens' power function.

The component PIII of the electroretinogram representing the optic generator potential was recorded after stimulation with short stimuli with different light intensity. It is shown that the impulse response function of a linear second order model with intensity-dependent coefficients can be well fit to the recordings. Two of its parameters, after logarithmic transformations, are linearly dependent on the luminance while the third parameter varies only within a small interval. It is therefore possible to describe the relation between PIII and luminance in a linearized second order model. Furthermore, both the type of the function relating the gain of the model to the luminance and its exponent are nearly identical with the psychophysic function relating luminance to subjective brightness. Further physiological implications are also considered.

Animals↗

PubMed2001

Distinction of different fingers by the frequency of stimulus induced beta oscillations in the human EEG.

Induced beta oscillations were studied in three normal subjects after mechanical stimulation of each fingertip of the right hand. For stimulation short tactile stimuli of 10 ms duration were presented at intervals of 4 s. The electroencephalogram was recorded with 60 closely spaced electrodes and sampled at 256 Hz. For each subject the reactive beta band was determined by comparing 1-s power spectra. The largest beta power increase was found in the range of 12-28 Hz on electrodes overlying the left-hand area. The Matching Pursuit algorithm was applied to single trials data and the frequency of single "atoms" determined. In one subject the little finger showed a significant higher frequency as compared to the thumb. The difference in frequency was in the order of 1 Hz.

Adult↗

PubMed2002

In vitro expression of the endothelial phenotype: comparative study of primary isolated cells and cell lines, including the novel cell line HPMEC-ST1.6R.

Endothelial cell lines are commonly used in in vitro studies to avoid problems associated with the use of primary endothelial cells such as the presence of contaminating cells, the difficulty in obtaining larger numbers of cells, as well as the progressive loss of cell viability and expression of endothelial markers in the course of in vitro propagation. We have analyzed the characteristics defining distinctive endothelial phenotypes in the cell lines EA.hy926, ECV304, EVLC2, HAEND, HMEC-1, ISO-HAS-1 and a cell line recently generated in our laboratory, HPMEC-ST1.6R, and have compared these phenotypes with those found in primary human endothelial cells isolated from umbilical vein (HUVEC), lung (HPMEC), and skin (HDMEC). The analysis revealed significant differences in phenotype expression between primary cells and the cell lines. Constitutive expression of von Willebrand factor, CD31, and CD34 and induced expression of cell adhesion molecules, ICAM-1, VCAM-1, and E-selectin and cytokines, IL-6, IL-8, MCP-1, and GM-CSF on stimulation with proinflammatory stimuli, as well as the uptake of DiI-Ac-LDL and the formation of cord-like structures on Matrigel, were typically observed in the primary cells. However, most cell lines exhibited only a few of these endothelial characteristics. Only HPMEC-ST1.6R exhibited the major constitutive and inducible endothelial cell characteristics and showed an angiogenic response on Matrigel similar to that of primary HPMEC. Thus, HPMEC-ST1.6R will be a valuable in vitro model system in which to study pathomechanisms and angiogenesis of the mature microvascular endothelium in vitro.

Antigens, CD34↗

PubMed2003

[Involvement of actin in electrotonic conductivity in the mixed synapses of goldfish Mauthner neurons].

The effect of highly specific and selective actin-polymerizing and labelling agent, phalloidin, on electrotonic conductivity and structure of the mixed synapses of goldfish Mauthner neurons (MN) was studied. It was shown that the paired subthreshold electrostimulation of afferent input against a background of phalloidin application resulted in the average 80% increase of the amplitude of MN response to the second stimulus. In control group it increased by only 10% and was observed only after suprathreshold stimulation, while subthreshold stimuli were ineffective. We interpret these data as the manifestation of increased conductivity of the mixed synapses, induced by actin polymerization. At the ultrastructural level, phalloidin application at MN and their mixed synapses increased the size and number of actin-containing desmosome-like junctions, as well as the number of fibrillar bridges crossing their cleft. Using the phalloidin-colloid gold marker, the actin nature of these bridges was demonstrated. Interdependent morpho-functional changes found in the mixed synapses, provide the indication of actin involvement in the conduction of electrotonic signal through the mixed synapse. The bridges crossing the cleft of desmosome-like junction could be the structural substrate of this process.

Actins↗

PubMed1992

Experimental look at cochlear mechanics.

The mechanisms by which the organ of Corti is stimulated by acoustic stimuli are discussed on the basis of experimental observations. This discussion refers to the resonance theory as well as to the traveling wave (TW) theory. The measurement of the basilar membrane displacements, of the cochlear microphonic (CM) responses to pure tones and impulses, and the recording of the intracochlear acoustic pressure seem to indicate that, at least in the basal part of the cochlea and for frequencies up to the characteristic frequency of a given location, the cochlear responses do not exhibit large phase lags and long delays which characterize the one-dimensional long-wave models (in which a TW transports the energy along the cochlear partition). These experimental observations suggest that the cochlear partition is excited simultaneously as a whole, more or less like a bank of resonators, as proposed a long time ago by Helmholtz.

Acoustic Stimulation↗

PubMed2005

Electrical potentials indicate stimulus expectancy in the brains of ants and bees.

In vertebrates, and in humans in particular, so-called 'omitted stimulus potentials' can be electrically recorded from the brain or scalp upon repeated stimulation with simple stimuli such as light flashes. While standard evoked potentials follow each stimulus in a series, 'omitted stimulus potentials' occur when an additional stimulus is expected after the end of a stimulus series. These potentials represent neuronal plasticity and are assumed to be involved in basic cognitive processes. We recorded electroretinograms from the eyes and visually evoked potentials from central brain areas of honey bees and ants, social insects to which cognitive abilities have been ascribed and whose rich-behavioral repertoires include navigation, learning and memory. We demonstrate that omitted stimulus potentials occur in these insects. Omitted stimulus potentials in bees and ants show similar temporal characteristics to those found in crayfish and vertebrates, suggesting that common mechanisms may underlie this form of short-term neuronal plasticity.

Animals↗