Effect of nifedipine on electrical activity of the brain in rat

The anxiolytic effect of the calcium channel blockers nifedipine and verapamil was tested in mice using two test: the conditioned suppression of the motility test and the black and white box test. The nifedipine but not the verapamil, in low doses (0.1 mg/kg b.w), proved anxiolytic effect and both nifedipine and verapamil in high dose (1.6-2.5 mg/kg b.w) had anxiogenic properties. The anxiogenic effect was correlated with the capacity of the drugs to block the calcium channels and the anxiolytic effect of low doses of the nifedipine was considered to be produced by opening these structures. These data were considered important for a new future aboard of the treatment and pathophysiology of the anxiety.     

Effects of nicotine on neocortical electrical activity in rats

The present study investigates the effects of acute and repeated nicotine i.p. treatment on cortical EEG activity. Nicotine at 0.3 and 0.9 mg/kg, but not at 0.1 mg/kg, decreased high voltage spindles (HVSs). Nicotine at 2.7 mg/kg suppressed HVSs completely. Mecamylamine, a nicotinic cholinergic antagonist, increased HVSs at 5 and 7.5 mg/kg. Nicotine blocked the HVS induction induced by mecamylamine. Mecamylamine at 1.25 mg/kg antagonized the HVS suppressing action of nicotine at 0.3 mg/kg. The muscarinic cholinergic antagonist, scopolamine (0.2 mg/kg), increased the 1 to 20 Hz amplitude sum value, and this increase was blocked to some extent by the highest dose of nicotine (2.7 mg/kg). However, nicotine did not block the effect of a higher scopolamine (2.0 mg/kg) dose on the sum amplitude values. Mecamylamine at 2.5 and 7.5 mg/kg blocked the effect of nicotine at 2.7 mg/kg on the EEG sum amplitude values in scopolamine (0.2 mg/kg)-treated rats. The peripherally acting nicotinic and muscarinic cholinergic antagonists, hexamethonium and scopolamine methylbromide, had no effect on spectral EEG and HVS values. In quisqualic acid nucleus basalis-lesioned rats, a frontal cortical choline acetyltransferase depletion (-72%) and slowing of the EEG was observed. Nicotine could not restore EEG activity in nucleus basalis-lesioned rats. After repeated (10 days, three injections/day) administration of nicotine, no tolerance to the effects of either nicotine (0.9 mg/kg) on spontaneously occurring HVSs or nicotine (2.7 mg/kg) on the EEG change induced by scopolamine was observed. The present results show that nicotinic receptor stimulation desynchronizes neocortical EEG activity in normal animals, but this action disappears in basal forebrain-lesioned animals. Therefore, it is likely that the effects of nicotine in reversing EEG and behavioral abnormalities observed in Alzheimer's disease may be limited if the basal forebrain cell loss is extensive.     

Tinnitus and event-related activity of the auditory cortex

A neuromagnetic study in tinnitus patients and normal-hearing controls was performed with a modified contingent negative variation (CNV) paradigm. While the warning stimulus S1 was a tone burst at an intensity well above threshold, the imperative stimulus S2 was presented at a near threshold intensity because, in the majority of cases, the perceived loudness of tinnitus is very close to the threshold for a pure tone of the same frequency. Subjects had to respond to S2 by pressing a button until its offset was detected. In this case, instead of the usual sudden cut-off of the CNV after the perception of S2, a slow negative deflection develops, the post-imperative negative variation (PINV). Its initial portion probably indicates the development of a second initial CNV because the subject had to attend also to the offset of S2. The neuromagnetic data were analysed both in the time domain and in the frequency domain (short-time spectral analysis of the classical EEG bands). The time domain waveform as well as the spectrotemporal patterns of the MEG bands exhibited deviations from the normal pattern in several tinnitus subgroups, depending on the characteristics of tinnitus (tonal vs. noisiform, monaural vs. binaural) and on the stimulation conditions (tinnitus side vs. non-tinnitus side).     

Correlation between cognitive brain function and electrical brain activity in dementia of Alzheimer type

Enterocytes were detached from various parts of the digestive tract of chickens by treatment with DTT or with hyaluronidase. Isolated enterocytes were exposed to suspensions of the V4 strain of Newcastle disease virus (NDV). Removal of virus from the supernatant fluid was taken as evidence of binding of virus to enterocytes and residual virus was measured both by infectivity assay and by ELISA. Enterocytes from duodenum, jejunum, ileum, caecum, and rectum bound the virus; enterocytes from oesophagus, crop and proventriculus did not.     

Effects of muscle electrical activity on the transmission of developing neuromuscular junction

A prospective cohort study in a neonatal intensive care unit (ICU) was carried out to evaluate whether the incidence of infection in neonates receiving intestinal decolonization was reduced in comparison to those who did not. This study was performed after controling possible confounding infection risk factors. A total of 536 babies were screened in our ICU during the 27-month study period. Neonates were admitted to the ICU for different reasons: low weight, respiratory distress syndrome, acute fetal suffering, surgery, etc. The doctor in charge decided whether the baby should be decolonized or not, so this experimental study was non-random. Thus more of the babies with a greater risk of infection were decolonized more often than the other babies who were not so much at risk. In this study, babies were classified by type of decolonization given: a well-performed Selective Intestinal Decolonization (SID) was done (early and with three oral drugs: E polymyxin, tobramycin and nystatin): 10.8% of the babies; Incorrect SID (was begun late and/or less than three drugs were used): 16.7% of the babies; and Without SID (72.9%). Total nosocomial infection (NI) was 11.2%, catheter-associated sepsis was 42% of the total NI. When the NI incidence was directly compared among groups, it was lower in the group without SID, but infants with decolonization initially had more infection risk factor than the first group. For this reason, multiple logistic regression was used in order to stratify factors by infection probability, and correcting the existing bias.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of corticotropin-releasing factor on brain serotonergic activity

The serotonergic dorsal raphe nucleus is innervated by corticotropin-releasing factor (CRF) and expresses CRF receptors, suggesting that endogenous CRF impacts on this system. The present study characterized interactions between CRF and the dorsal raphe serotonin (5-HT) system. The effects of intracerebroventricularly (i.c.v.) administered CRF on microdialysate concentrations of 5-HT in the lateral striatum of freely moving rats were determined. CRF had biphasic effects, with 0.1 and 0.3 microgram decreasing, and 3.0 micrograms increasing 5-HT dialysate concentrations. i.c.v. administration of CRF inhibited neuronal activity of the majority of dorsal raphe neurons at both low (0.3 microgram) and high (3 micrograms) doses. Likewise, intraraphe administration of CRF (0.3 and 1.0 ng) had predominantly inhibitory effects on discharge rate. Together, these results suggest that CRF is positioned to regulate the function of the dorsal raphe serotonergic system via actions within the cell body region. This regulation may play a role in stress-related psychiatric disorders in which 5-HT has been implicated.     

Motor responses measured by brain electrical activity mapping.

Studied the brain electrical activity of 14 right-handed normal Ss (mean age 25 yrs) while they were exposed to motor performance tasks of increasing difficulty. Each task lasted 45–60 sec, and a 30-sec period of each task was analyzed by a spectrum analyzer. Data are presented in topographic maps showing the electrical activity for each task, in different frequency bands. Results show a bilateral decrease in amplitude in sensorimotor areas relative to baseline for a single hand movement. Tasks that required the programming of movement showed baseline–task differences in amplitude in additional areas: the right frontal area, the prefrontal area, the posterior parietal area, and the left temporal area. Findings suggest that different topographical areas are involved in motor tasks that require an increased level of programming. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of rho-chloroamphetamine on locomotor activity and brain 5-hydroxyindoles

The conversion of 14C-maltose into glucose, lactate and 14 CO2 was studied in perfused livers from fed and fasted rats and in isolated hepatocytes. Maximal glucose production was 30 mM x g-1 x h-1; half-maximal rates were found with 3 mM maltose. About 0.01 % of the radioactivity infused was recovered as 14CO2. The addition of maltose had no effect on rates of oxygen consumption, lactate production or ketogenesis. The data suggest that maltose did not serve as a major substrate for biosynthetic or energy producing processes under the conditions of the perfused rat liver.     

Extreme prematurity in healthy 5-year-old children: a re-analysis of sex effects on event-related brain activity

A male disadvantage has been reported in several outcome studies of children born preterm. Twenty-two healthy premature children (10 girls, 12 boys) born between 25 and 28 weeks of gestation and 20 controls born full-term (10 boys, 10 girls) were matched on socioeconomical status and age. Event-related potentials (ERPs) were recorded by using 14 electrodes in a visual oddball task, with 75% frequent and 25% rare stimuli. This task elicited a larger P3 to the rare than to the frequent stimuli, with a prominent parietocentral localization. However, the amplitude was larger in full-term boys than in full-term girls, a difference that was not observed between preterm boys and preterm girls, especially to targets and on the central electrodes. In addition, the preterm group was characterized by a frontal slow wave larger in boys than in girls. In these prematures, the lack of the sex-related difference may be accounted by differences in the strength of the neuronal generators in males, as they might have been affected by the high level of androgens by the fetal testis under the control of placental gonadotropes during the first two thirds of gestation.     

Alcohol abuse and traumatic brain injury: effect on event-related potentials

OBJECTIVE: To examine the individual and combined impact that traumatic brain injury (TBI) and heavy social use of alcohol have on electrophysiologic correlates of working memory and evaluation of task-relevant information. DESIGN: Case-control study. SETTING: University hospital brain injury rehabilitation unit. PARTICIPANTS: Forty male volunteers divided into four groups on the basis of their history of TBI and alcohol intake. Subjects with TBI had experienced a severe closed head injury at least 1 year before testing. MAIN OUTCOME MEASURE: Event-related potentials (ERPs) and neuropsychometric tests. RESULTS: Groups showed no significant differences in average age or neuropsychological tests. TBI groups did not differ in time postinjury or on severity measures. Alcohol use measures were significantly greater in the two alcohol groups. N200 latency and P300 amplitude were impaired in heavy social drinkers and in nondrinking subjects with TBI relative to controls, but were significantly impaired in subjects with TBI who were also heavy social drinkers. CONCLUSION: The results indicate that although alcohol use and TBI independently produce mile alterations in some aspects of late ERP components, the ERP changes are significantly greater when alcohol use and TBI are combined. This study provides evidence that heavy social drinking after TBI has a measurable impact on electrophysiologic correlates of cognition.     

Effects of contralateral speech competition on auditory event-related potentials recorded from elderly listeners: brain map study

Topographic brain mapping was used to investigate the ability of young and elderly female listeners to attend to tones at one ear in the presence of speech competition at the opposite ear. An oddball stimulus presentation paradigm was used to record the N1, P2, and P300 components of the late auditory evoked potential from 19 scalp locations. With speech competition, elderly listeners exhibited significantly larger reductions in N1 amplitude than did young listeners. This suggests that N1 may provide an electrophysiologic index of age-related breakdowns in processing sounds in the presence of background competition. An unexpected difference was also found between young and elderly listeners in P300 scalp topography. While the young listeners' P300 response was centered at midline for both left and right ear stimulation, the elderly participants had P300 maxima centered in the parietal area of the hemisphere located contralateral to the test ear. This suggests that some of the functional properties (e.g., timing, strength, orientation) of the P300 neural generators may change with age or, alternatively, that different generators may be operative in elderly listeners.     

Development of telemetric techniques for use in studies of the electrical activity of the brain

A telemetry system has been designed to transmit two channels of wideband activity (0.2 Hz-2.5 KHz) recorded from high-impedance microelectrodes in the brains of free-moving cats. Thus, both unit activity and slow-wave field activity are accessible without disruption of the animals' behavior. In addition, circuitry is described that conditions the receiver signals, that dicriminates valid subcarrier signals from receiver noise and that automatically aborts data output in the absence of discriminable subcarrier. This receiver signal processing circuitry thus assures the fidelity of the decoded subcarrier, greatly facilitates further machine processing of the data and frees the experimenter from having to continuously monitor the receiver signals to subjectively edit out noisy data.     

Effects of prostaglandin E2 and oxytocin on the electrical activity of hormone-treated and pregnant rat myometria

1. The membrane properties of the rat myometrium, during gestation and following ovarian hormone treatment, have been investigated with the micro-electrode technique. 2. Spontaneously generated bursts of electrical activity alternating with silent periods were recorded from non-pregnant, pregnant and post-partum myometria. The membrane potential was highest during the middle stage of gestation, but the spike amplitude within a burst was not uniform. In the final stage of gestation and during parturition, the membrane potential was low and the spikes within a burst were of low frequency and uniform amplitude. 3. During parturition and post-partum, a gradual depolarization of the membrane, accompanied by an increase in membrane resistance, occurred before the generation of a burst. 4. Excitability of the membrane fluctuated from a peak just before the generation of a burst to a low after the cessation of a burst. 5. Displacement of the membrane potential by electrical current or by lowering the temperature modified the slope spontaneous depolarization, but the fluctuations of excitability persisted. The Q10 value for the frequency of spontaneous bursts, measured between 36 and 30 degrees C, was 3-8. 6. Hyperpolarization of the membrane increased the maximum rate of rise of the spike, but beyond -70 mV, the rate of rise was reduced. Half-inactivation of spike generation of spike generation occurred at a membrane potential less negative than the interburst potential, indicating that the current carrying system was not fully activated during parturition. 7. In both normal and spayed rats, oestradiol hyperpolarized the membrane and the burst of spikes was generated hyperpolarized the membrane and the burst of spikes was generated on a sustained depolarization. Progesterone slightly hyperpolarized the membrane and burst discharges occurred without a sustained depolarization. Simultaneous treatment with progesterone and oestradiol produced a plateau potential of long duration during burst discharges. 8. The thickness of the muscle layer, length constant of the tissue and time constant of the membrane were measured during gestation and from spayed rats under various hormonal conditions. The length constant of the tissue was increased by oestradiol and was further increased by simultaneous treatment withoestradiol and progesterone. The increase in tissue thickness appeared to have the most marked influence on the length constant. 9. The resting and active membrane properties of the progresterone treated myometrium were similar to those observed during the middle stages of gestation. The oestradiol-treated myometrium did not resemble that during the last stages of gestation and parturition, which was simulated by combination of the two hormones, oestradiol preceding progesterone.