Physiologic and pathophysiologic relationship between the electroencephalogram and the regional cerebral blood flow

Mitigation of electroencephalographic and cardiovascular responses to castration in Bos indicus bulls following the administration of either lidocaine or meloxicam

OBJECTIVE

To investigate the mitigating effects of administration of local anaesthetic or systemic meloxicam on the electroencephalographic (EEG) and cardiovascular responses during surgical castration of Bos indicus bull calves.

STUDY DESIGN

Prospective, randomized, experimental study.

ANIMALS

Thirty-six 6-8 month-old Bos indicus bull calves, with a mean ± standard deviation weight of 237 ± 19 kg.

METHODS

Animals were allocated randomly to three groups of 12 (group L, 260 mg of 2% lidocaine subcutaneously and intratesticularly 5 minutes prior to castration; group M, 0.5 mg kg^-1 of meloxicam subcutaneously 30 minutes prior to castration; group C, no preoperative analgesia administered). Anaesthesia was induced and maintained with halothane (0.9-1.1%) in oxygen. Electroencephalogram, heart rate (HR) and mean blood pressure (MAP) were recorded for 300 seconds prior to (baseline, B) and from the start of surgery (first testicle removal, T1). HR and MAP were compared at 10 second intervals for 90 seconds from the start of T1. Median frequency (F₅₀), spectral edge frequency (F₉₅) and total power of the EEG (P_tot) were analysed using area under the curve comparing T1 to B.

RESULTS

All EEG variables were significantly different between B and T1 (p ≤ 0.0001). No differences in F₅₀ were found between groups during T1 (p = 0.6491). F₉₅ and P_tot were significantly different between group L and groups C and M during T1 (p = 0.0005 and 0.0163, respectively). There were transient significant changes in HR and MAP in groups L and M compared to group C during the 20-50 second periods.

CONCLUSIONS

The EEG changes indicate nociceptive responses in all three groups during surgical castration, greater in group L compared to groups C and M. Both analgesics attenuated the peracute cardiovascular response. Lidocaine and meloxicam administered prior to castration attenuated these responses in Bos indicus bull calves.

CLINICAL RELEVANCE

These findings provide support for the preoperative administration of lidocaine and potentially meloxicam for castration in Bos indicus bull calves.

Physiology Of Drowning: A Review

Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated cardiorespiratory responses to skin and deep body temperature, including cold shock, physical incapacitation, and hypovolemia, as precursors of collapse and submersion. The physiology of submersion includes fear of drowning, diving response, autonomic conflict, upper airway reflexes, water aspiration and swallowing, emesis, and electrolyte disorders. Submersion outcome is determined by cardiac, pulmonary, and neurological injury. Knowledge of drowning physiology is scarce. Better understanding may identify methods to improve survival, particularly related to hot-water immersion, cold shock, cold-induced physical incapacitation, and fear of drowning.

Neurophysiological evidence for cognitive and brain functional adaptation in adolescents living at high altitude

OBJECTIVE

Neurophysiological methods were used to study the effects of high altitude living on brain functions in a subgroup of participants of the Bolivian Children Living at Altitude (BoCLA) project.

METHODS

Electroencephalogram (EEG), event-related potentials (ERP) and cerebral blood flow velocity (CBFV) were recorded in two groups of adolescents (aged 13-16 years), living either at sea-level or high altitude (~3700m).

RESULTS

Neuropsychological testing revealed no deficits in the high altitude group, despite significantly reduced blood oxygen saturation. In agreement, ERPs elicited by oddball target detection and choice reaction time tasks were not different between groups. In contrast, resting state EEG showed reductions in delta and beta frequency amplitudes in adolescents living at high altitude. The EEG attenuations were correlated with lower CBFV, and the EEG group differences diminished during task performance.

CONCLUSIONS

No indication was found for negative sequelae of chronic hypoxia in adolescents born and living at an altitude of ~3700m, rather evidence for successful neurophysiological adaptation was found under such conditions.

SIGNIFICANCE

Dynamic regulation of metabolic demand is one adaptive mechanism that preserves cognitive development at high altitude.

Interaction of hypocapnia, hypoxia, brain blood flow, and brain electrical activity in voluntary hyperventilation in humans

Changes in various physiological measures in voluntary hyperventilation lasting three minutes or more in humans were studied and compared. Three-minute hyperventilation, in which the rate of external ventilation increased by an average factor of 4.5-5, produced similar phasic changes in central and brain hemodynamics. The rate of circulation, indicated by rheographic data, initially increased during hyperventilation, reaching a maximum at 1-2 min of the test; there was then a reduction, to a minimum 2-3 min after the end of the test; this was followed by a further slow increase. The rate of cerebral blood flow during all 3 min of hyperventilation remained elevated in most subjects as compared with baseline and decreased during the 5 min following the end of the test. Transcutaneous carbon dioxide tension changed differently - there was a decrease to a minimum (about 25 mmHg) by the end of the test, lasting 1 min from the end of the test, this being followed by an increase to a level of 90% of baseline at 5 min after the test. Blood oxygen saturation remained at 98-100% during the test, decreasing to about 90% 5 min after the test; this, along with the decrease in cerebral blood flow, was a factor producing brain hypoxia. In different subjects, changes in the spectral power of oscillations in different EEG ranges on hyperventilation were "mirrored" to different extents by the dynamics of transcutaneous carbon dioxide tension. The duration and repetition of hyperventilation were important factors for understanding the interaction between brain hemodynamics, hypocapnia, hypoxia, and brain electrical activity. After several repetitions of 3-min hyperventilation over a period of 1 h, the increasing brain blood flow could decrease significantly on the background of relatively small changes in brain electrical activity. The data presented here were assessed from the point of view of the important role of brain tissue oxygen utilization mechanisms in adaptation to hypoxia and hypocapnia.

Neural correlates of regional EEG power change

To clarify the physiological significance of task-related change of the regional electroencephalogram (EEG) rhythm, we quantitatively evaluated the correlation between regional cerebral blood flow (rCBF) and EEG power. Eight subjects underwent H2 15O positron emission tomography scans simultaneously with EEG recording during the following tasks: rest condition with eyes closed and open, self-paced movements of the right and left thumb and right ankle. EEG signals were recorded from the occipital and bilateral sensorimotor areas. Cortical activation associated with EEG rhythm generation was studied by the correlation between rCBF and EEG power. There were significant negative correlations between the sensorimotor EEG rhythm at 10-20 Hz on each side and the ipsilateral sensorimotor rCBF and between the occipital EEG rhythm at 10-20 Hz and the occipital rCBF. The occipital EEG rhythm showed a positive correlation with the bilateral medial prefrontal rCBF, while the right sensorimotor EEG rhythm showed a positive correlation with the left prefrontal rCBF. In conclusion, decrease in the regional EEG rhythm at 10-20 Hz might represent the neuronal activation of the cortex underlying the electrodes, at least for the visual and sensorimotor areas. The neural network including the prefrontal cortex could play an important role to generate the EEG rhythm.

Investigation of changes in the middle latency auditory evoked potential during anesthesia with sevoflurane in dogs

OBJECTIVE

To investigate the middle latency auditory evoked potential (MLAEP) in awake dogs and dogs anesthetized with 2 concentrations of sevoflurane.

ANIMALS

10 adult Beagles.

PROCEDURE

The MLAEP was recorded while dogs were awake and anesthetized with sevoflurane (end-tidal concentration, 2.7% or 3.5%). Three needle electrodes were inserted SC, and click stimuli were delivered biaurally. Signal acquisition, averaging, and analysis were performed by use of computer software developed in-house. Signals were recorded for 128 milliseconds, and the responses to 1,024 stimuli were averaged. Waveforms from 10 recordings in each dog were averaged, and latencies of peaks were measured. Data acquired for awake dogs and dogs anesthetized with high and low sevoflurane concentrations were compared statistically.

RESULTS

Sevoflurane anesthesia attenuated the MLAEP so that only peaks P0, Na, and Pa could be identified. The MLAEP changes were maximal at the lower concentration of sevoflurane evaluated. The latencies of these peaks were significantly shorter in awake dogs, compared with values in anesthetized dogs. No difference in the peak latency was detected between the sevoflurane concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

In terms of CNS responsiveness, the effects of anesthesia with sevoflurane are similar to those of anesthesia with isoflurane. Data suggest that sevoflurane is not the inhalant agent of choice in a research setting where electroencephalographic measurements are to be recorded during anesthesia. The depression of the MLAEP waveform by sevoflurane also suggests that the MLAEP is not a suitable tool with which to monitor anesthetic depth during sevoflurane anesthesia in dogs.

Investigation of the EEG effects of intravenous lidocaine during halothane anaesthesia in ponies

OBJECTIVE

To record the electroencephalographic changes during castration in ponies anaesthetized with halothane and given intravenous (IV) lidocaine by infusion. The hypothesis tested was that in ponies, IV lidocaine is antinociceptive and would therefore obtund EEG changes during castration.

ANIMALS

Ten Welsh mountain ponies referred to the Department of Clinical Veterinary Medicine, Cambridge for castration under general anaesthesia.

MATERIALS AND METHODS

Following pre-anaesthetic medication with intramuscular acepromazine (0.02 mg kg(-1)) anaesthesia was induced with IV guaiphenesin (60 mg kg(-1)) and thiopental (9 mg kg(-1)) and maintained with halothane at an end-tidal concentration (FE'HAL) of 1.2%. A constant rate infusion of IV lidocaine (100 microg kg(-1) minute(-1)) was administered throughout anaesthesia. The electroencephalogram (EEG) was recorded continuously using subcutaneous needle electrodes. All animals were castrated using a closed technique. The raw EEG signal was analysed after completion of each investigation, and the mean values of EEG variables (median frequency, spectral edge frequency, total amplitude) recorded during a baseline period (before surgery began) and the removal of each testicle were compared using anova for repeated measures.

RESULTS

Spectral edge frequency (SEF) 95% decreased during removal of the second testicle compared with baseline recordings. No other significant EEG changes during castration were measured.

CONCLUSIONS

Lidocaine obtunded the EEG changes identified during castration in a previous control study, providing indirect evidence that lidocaine administered peri-operatively was antinociceptive and contributed to anaesthesia during castration.

CLINICAL RELEVANCE

The antinociceptive effect of lidocaine combined with its minimal cardiovascular effects indicate a potential use for systemic lidocaine in clinical anaesthetic techniques.

Increased cortical cerebral blood flow with LUCAS; a new device for mechanical chest compressions compared to standard external compressions during experimental cardiopulmonary resuscitation

OBJECTIVE

LUCAS is a new device for mechanical compression and decompression of the chest during cardiopulmonary resuscitation (CPR). The aim of this study was to compare the efficacy of this new device with standard manual external chest compressions using cerebral cortical blood flow, cerebral oxygen extraction, and end-tidal CO2 for indirect measurement of cardiac output. Drug therapy, with adrenaline (epinephrine) was eliminated in order to evaluate the effects of chest compressions alone.

METHODS

Ventricular fibrillation (VF) was induced in 14 anaesthetized pigs. After 8 min non-intervention interval, the animals were randomized into two groups. One group received external chest compressions using a new mechanical device, LUCAS. The other group received standard manual external chest compressions. The compression rate was 100 min(-1) and mechanical ventilation was resumed with 100% oxygen during CPR in both groups. No adrenaline was given. After 15 min of CPR, external defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). Cortical cerebral blood flow was measured continuously using Laser-Doppler flowmetry. End-tidal CO2 was measured using mainstream capnography.

RESULTS

During CPR, the cortical cerebral blood flow was significantly higher in the group treated with LUCAS (p = 0.041). There was no difference in oxygen extraction between the groups. End-tidal CO2, an indirect measurement of the achieved cardiac output during CPR, was significantly higher in the group treated with the LUCAS device (p = 0.009). Restoration of spontaneous circulation was achieved in two animals, one from each group.

CONCLUSIONS

Chest compressions with the LUCAS device during experimental cardiopulmonary resuscitation resulted in higher cerebral blood flow and cardiac output than standard manual external chest compressions. These results strongly support prospective randomised studies in patients to evaluate this new device.

Psychobiology of altered states of consciousness

The article reviews the current knowledge regarding altered states of consciousness (ASC) (a) occurring spontaneously, (b) evoked by physical and physiological stimulation, (c) induced by psychological means, and (d) caused by diseases. The emphasis is laid on psychological and neurobiological approaches. The phenomenological analysis of the multiple ASC resulted in 4 dimensions by which they can be characterized: activation, awareness span, self-awareness, and sensory dynamics. The neurophysiological approach revealed that the different states of consciousness are mainly brought about by a compromised brain structure, transient changes in brain dynamics (disconnectivity), and neurochemical and metabolic processes. Besides these severe alterations, environmental stimuli, mental practices, and techniques of self-control can also temporarily alter brain functioning and conscious experience.

Intrathecal adenosine increases spinal cord blood flow in the rat: measurements with the laser-Doppler flowmetry technique

BACKGROUND

Adenosine and adenosine analogues induce antinociception both after systemic and intrathecal (i.t.) administration in animal models. Further, patients with neuropathic pain have been treated successfully with i.t. adenosine. Prior to introducing new analgesic drugs for regular spinal use in humans, experimental studies must be undertaken to evaluate the risks of neurotoxicity. It is important to evaluate the possibility of cytotoxic effects and that antinociception may be due to decreased spinal cord blood flow (SCBF) and neural ischaemia. The present study evaluates whether adenosine or isotonic mannitol induces changes in SCBF as assessed by laser-Doppler flowmetry (LDF).

METHODS

After laminectomy and insertion of i.t. catheters, seven rats received adenosine 50 microg in isotonic mannitol 500 microg, six rats received isotonic mannitol 500 microg and eight rats received saline 0.9%. SCBF was registered by the LDF technique continuously for 3 h after injection. Arterial blood pressure was also assessed.

RESULTS

In the adenosine in mannitol group, SCBF increased up to 230% of baseline levels for almost 40 min, P = 0.044 and then declined. In the mannitol group, SCBF increased up to 180% of baseline (P < 0.011) before declining. At 60 min, SCBF had returned to saline levels and remained stable during the rest of the experiment.

CONCLUSION

Intrathecal administration of adenosine in mannitol and of mannitol both increased SCBF in rats, compared with saline. It is unlikely that the effects on SCBF induced by adenosine and mannitol could result in neurotoxicity of the spinal cord.

Changes in the EEG during castration in horses and ponies anaesthetized with halothane

OBJECTIVE

To identify changes in the amplitude spectrum of the electroencephalogram (EEG) during a standardized surgical model of nociception in horses.

ANIMALS

Thirteen entire male horses and ponies referred to Division of Clinical Veterinary Science, Bristol (n = 9) and Department of Clinical Veterinary Medicine (n = 4) for castration.

MATERIALS AND METHODS

Following pre-anaesthetic medication with acepromazine, anaesthesia was induced with guaiphenesin and thiopental and maintained with halothane in oxygen. The EEG was recorded continuously using subcutaneous needle electrodes. Additional monitoring comprised ECG, arterial blood pressure, blood gas analysis, airway gases, and body temperature. All animals were castrated using a closed technique. The raw EEG was analysed after completion of each investigation and the EEG variables median frequency (F50), spectral edge frequency (SEF) 95% and total amplitude were derived from the spectra using standard techniques. The mean values of EEG variables recorded during a baseline time period (recorded before the start of surgery) and castration of each testicle were compared using analysis of variance for repeated measures.

RESULTS

Total amplitude (Atot) decreased and F50 increased during castration of each testicle compared to the baseline time period [(89.0 +/- 7.8% testicle 1, 87.0 +/- 7.8% testicle 2) and (110.0 +/- 15.0% testicle 1, 109.0 +/- 15.0% testicle 2), respectively]. Changes in SEF 95% were not significant.

CONCLUSIONS

De-synchronization was identified in the EEG during the nociceptive stimulus of castration. The results suggest that an increase in F50 may be a specific marker for nociception in the horse.

CLINICAL RELEVANCE

Studies investigating the efficacy of analgesic agents in horses are limited by difficulties in peri-operative pain assessment. This model, using EEG changes associated with nociceptive stimulation, can be used to investigate the anti-nociceptive efficacy of different anaesthetic agents in the horse.

Gender differences in cerebral blood flow and oxygenation response during focal physiologic neural activity

Using functional magnetic resonance imaging techniques CBF and oxygenation changes were measured during sustained checkerboard stimulation in 38 right-handed healthy volunteers (18 men and 20 women). The average blood oxygenation level dependent (BOLD) contrast technique signal intensity change was 1.67 +/- 0.6% in the group of male volunteers and 2.15 +/- 0.6% in the group of female volunteers (P < .05). Baseline regional CBF (rCBF) values in activated gray matter areas within the visual cortex were 57 +/- 10 mL x 100 g(-1) x min(-1) in women and 50 +/- 12 mL x 100 g(-1) x min(-1) in men, respectively (P = .09). Despite a broad overlap between both groups the rCBF increase was significantly higher in women compared to men (33 +/- 5 mL x 100 g(-1) x min(-1) versus 28 +/- 4 mL x 100 g(-1) x min(-1), P < .01). The increase of rCBF was not correlated with the baseline rCBF (mL x 100 g(-1) x min(-1)) (r(s) = 0.01, P = .9). Moreover, changes of rCBF were not correlated with changes in BOLD signal intensities (r(s) = 0.1, P = .7). Enhanced rCBF response in women during visual stimulation could be related to gender differences in visual physiology or may reflect gender differences in the vascular response to focal neuronal activation. Gender differences must be considered when interpreting the results of functional magnetic resonance imaging studies.

Effects of alfentanil on the equine electroencephalogram during anaesthesia with halothane in oxygen

Opioids have variable effects on the minimum alveolar concentration of inhaled anaesthetics in the horse. During halothane anaesthesia at an end-tidal halothane concentration between 0.75 and 0.85 percent, the electroencephalogram (EEG) frequency power spectrum and the auditory evoked potential were recorded continuously in eight ponies during an infusion of approximately 40 micrograms kg-1 alfentanil over five minutes, and for a further 55 minutes. The spectral edge and median frequency of the EEG and the mid-latency of the auditory evoked potential at the time of maximum change of these variables were compared with those recorded before the start of the infusion. The mean (SD) spectral edge and median frequencies were reduced by 26 (5) percent and 36 (6) percent respectively. The mid-latency of the auditory evoked potential did not change. These cortical effects of alfentanil in the horse are qualitatively the same as in other species, suggesting that the alfentanil-induced excitement observed in horses in not of cortical origin.

Role of bedside electroencephalography in the adult intensive care unit during therapeutic neuromuscular blockade

BACKGROUND: Size, weight and technical difficulties limit the use of ponderous strip chart electroencephalographs (EEGs) for real time evaluation of brain wave function in modern intensive care units (ICUs). Portable, computer processed, bedside EEGs provide real time brain wave appraisal for some brain functions during therapeutic neuromuscular blockade when the visual clues of the cerebral function disappear. RESULTS: Critically ill ICU patients are frequently placed in suspended animation by neuromuscular blockade to improve hemodynamics in severe organ system failure. Using the portable bedside EEG monitor, several cerebral functions were monitored continuously during sedation of selected patients in our ICU. CONCLUSIONS: The processed EEG is able to continuously monitor the end result of some therapeutics at the neuronal level when natural artifacts are suppressed or eliminated by neuromuscular blockade. Computer processed EEG monitoring may be the only objective method of assessing and controlling sedation during therapeutic musculoskeletal paralysis.

Improvement of functional magnetic resonance images by pretreatment of data

Functional magnetic resonance images of the brains of subjects performing the finger-tapping paradigm were made using a conventional technique. Two threshold values for the pixels were obtained by analysing pixel by pixel the distributions of the means and variances of each subject's images for 20 consecutive scans, both while performing the task and while at rest. Considerable signal improvement in the final images was achieved by removing from our data all pixels beyond these threshold values (mean < or = 16 and variance > or = 7).

Impairment of blood-brain barrier function by serotonin induces desynchronization of spontaneous cerebral cortical activity: experimental observations in the anaesthetized rat

The possibility that elevation of serotonin in the circulation, which is found in various pathological states, influences the spontaneous cerebral cortical activity was examined in a rat model. The electroencephalogram was recorded using bipolar epidural electrodes placed over the frontal and parietal cerebral cortex. Intravenous infusion of serotonin (10 micrograms/kg per min for 10 min) decreased the electroencephalogram amplitude in both frontal and parietal recordings within 4 min of infusion. This decrease in amplitude was reversible, Pretreatment with cyproheptadine (a potent serotonin2 receptor antagonist) prevented the serotonin-induced decrease of the electroencephalogram amplitude. The blood-brain barrier permeability to Evans Blue and [131I]sodium was increased in frontal and parietal cortex. This increase in blood-brain barrier permeability was absent in animals pretreated with cyproheptadine. These results provide direct evidence that an elevated level of serotonin in blood has the capacity to influence spontaneous cortical electrical activity. This effect of serotonin on electroencephalogram appears to be due to its ability to enter into the brain parenchyma by inducing a short-term breakdown of the blood-brain barrier, probably via serotonin2 receptors.

Preoperative cerebrovascular symptoms and electroencephalographic abnormalities do not predict cerebral ischemia during carotid endarterectomy

BACKGROUND AND PURPOSE

The purpose of this prospective study was to establish (1) whether patients with neurological symptoms scheduled for carotid endarterectomy had an increased incidence of electroencephalographic (EEG) abnormalities during awake baseline recordings, (2) whether these symptoms and EEG abnormalities predicted ischemic EEG pattern changes at carotid artery cross-clamp, and (3) whether there was an association between age, presence of EEG baseline abnormalities, and ischemic pattern changes at carotid artery cross-clamp.

METHODS

We reviewed the medical record of each patient scheduled to undergo carotid endarterectomy and recorded the patient's age and history of previous neurological symptoms. We then continuously monitored and analyzed 16 channels of anteroposterior bipolar EEG and two of referential derivations from at least 5 minutes before induction of anesthesia and throughout the operation.

RESULTS

We completed 394 consecutive studies. Preoperative neurological symptoms were related to EEG abnormalities in awake patients (P < .001) and to EEG asymmetries in anesthetized patients (P < .001). Abnormal awake EEG findings were associated with asymmetries after anesthesia (P < .0001). Twenty-eight percent of both symptomatic (70/249) and asymptomatic (41/145) patients had EEG ischemic pattern changes at carotid artery cross-clamp. Neither neurological symptoms nor EEG abnormalities were associated with age or the development of EEG ischemic pattern changes at carotid artery cross-clamp.

CONCLUSIONS

Despite the strong association between a history of cerebral ischemic symptoms and preoperative EEG abnormalities in patients undergoing carotid endarterectomy, patients who have suffered strokes or transient ischemic events are at no greater risk of having EEG evidence of cerebral ischemia during carotid artery cross-clamp than patients without symptoms and with normal baseline EEGs. We conclude that preoperative EEG abnormalities in symptomatic patients are not due to age or to insufficiency of regional cerebral blood flow.

EEG changes following increased blood-brain barrier permeability under long-term immobilization stress in young rats

A continuous 8 h of immobilization stress in conscious young rats increased the blood-brain barrier (BBB) permeability to 131I-sodium in 12 out of 14 brain regions studied. A flattening of electroencephalographic (EEG) activity was noted during this time period. The mean cerebral blood flow (CBF) was reduced by 17% (during this time period) but the regional flow reduction was not related to the regional increase in BBB permeability. On the other hand, a correlation was observed between increased plasma and brain 5-HT levels and increased BBB permeability. p-Chloro-phenylalanine (p-CPA) pretreatment has prevented the occurrence of increased BBB permeability, and the flattening of EEG activity as well as 5-HT levels in plasma and brain. These results suggest that the long-term immobilization stress induces causally related sequential events in rats: enhancement of circulating 5-HT, impairment of BBB, free access of 5-HT into the brain, and eventually flattening of EEG.

Influence of long-term acute heat exposure on regional blood-brain barrier permeability, cerebral blood flow and 5-HT level in conscious normotensive young rats

Exposure of conscious young rats to 4 h heat stress at 38 degrees C in B.O.D. incubator was associated with increased blood-brain barrier (BBB) permeability in 14 brain regions studied. In the same regions cerebral flow (CBF) diminished by 4-65%, but the magnitude of flow reduction was not correlated with the degree of increased BBB permeability. On the other hand, a correlation was observed with increased plasma and brain 5-hydroxytryptamine (5-HT) levels. p-Chlorophenylalanine (p-CPA), indomethacin and diazepam pretreatment prevented both the increased BBB permeability and 5-HT levels following heat exposure. Whereas cyproheptadine and vinblastine pretreatment prevented the increased BBB permeability alone. The probable mechanism(s) underlying the BBB permeability is discussed.

EEG mapping of left hemisphere dysfunction during motor performance in schizophrenia

With a newly developed system of brain electrical activity mapping we studied 10 right-handed, neuroleptic-treated schizophrenics (five of the disorganized, five of the paranoid type, corresponding to 295.1 and .3 in DSM-III), compared with 10 normal controls. Increasingly complex motor tasks were used for cortical activation, all functional states being referenced to resting states recorded after a special relaxation program. We found higher delta and theta amplitudes during rest, as noted in previous studies, and lower beta power values. As a major result, however, we found a widespread left hemisphere dysfunction in schizophrenics, predominantly in the left primary sensory and motor areas. Additionally, we found signs of a "compensatory" overactivation in patients in motor tasks, when this hemisphere is not "used" by normal persons. The results support our findings obtained with this method during multisensory motor coordination in schizophrenia. The results in these patients suggest that these are not merely vigilance, attention, or motivation dysfunctions, but rather specific cortical correlates of impaired motor performance.

Influence of long-term immobilization stress on regional blood-brain barrier permeability, cerebral blood flow and 5-HT level in conscious normotensive young rats

Eight hours immobilization stress in young rats has increased the blood-brain barrier (BBB) permeability in 12 out of 14 brain regions studied. In the same regions cerebral blood flow (CBF) diminished by 2-37%, but the magnitude of flow reduction was not correlated with the degree of increased BBB permeability. On the other hand, a correlation was observed with increased plasma and brain 5-HT levels. The increased BBB permeability and increased 5-HT levels were prevented by pretreatment with p-CPA, indomethacin and diazepam. Cyproheptadine and vinblastine pretreatment prevented the occurrence of increased BBB permeability alone. The probable mechanism(s) underlying the breakdown of BBB permeability is discussed.

Effects of bradykinin on pial arteries and arterioles in vitro and in situ

The effect of bradykinin on cerebrovascular resistance vessels was investigated by the use of in vitro and in situ preparations. Bradykinin, in the range of 10(-10) to 10(-5) M, elicited a concentration-dependent vasodilatation on both feline and human pial arteries in vitro; the half-maximal response was found to be approximately at 2.8 X 10(-7) M and 1.3 X 10(-8) M (EC50), respectively. This dilatatory effect of bradykinin in vitro was found only in arteries preconstricted with prostaglandin F2 alpha or 5-hydroxytryptamine. In order to determine the effects of bradykinin on the diameter of cat pial arteries in situ, perivascular microapplication was employed. The dose-response curves obtained showed vasodilatation; the EC50 and the maximal response (EAm) were 4.4 X 10(-7) M and 45.5% at 10(-5) M, respectively. Statistically significant (p less than 0.01) reactions were observed at 10(-7) M and higher concentrations of bradykinin. The observed effects were independent of initial vessel size (80-260 microns). These in situ findings are very similar to those found in vitro. The isolated guinea pig ileum was used to check the stability of the bradykinin solutions. In this instance, a concentration-dependent contraction was found when "freshly prepared" or "5 hours stored" bradykinin was applied, indicating no measureable degradation of bradykinin. We conclude that bradykinin is a powerful vasodilator of both human and feline pial arteries.

Cerebral blood flow in chronic toxic encephalopathy in house painters exposed to organic solvents

Cerebral blood flow (CBF) was studied in 11 controls and 9 house painters occupationally exposed to organic solvents for a mean of 22 years. They had mild to moderate intellectual impairment, and no or only minor cerebral atrophy was seen in a CT-scan of the brain. The 133Xe inhalation technique was used and the flow was calculated from the initial slope of the 133Xe wash out curve (ISI). ISI averaged 36.8 ml/100 g/min in the painters and 45.4 ml/100 g/min in the controls, representing a significant difference (P less than 0.05). The reduced CBF in these painters with slight to moderate intellectual impairment might be due to limited neuronal loss or to permanently decreased metabolism of the neurones.

Local cerebral blood flow following transient cerebral ischemia. II. Effect of arterial PCO2 on reperfusion following global ischemia

Following 5 minutes of global ischemia, local cerebral blood flow (LCBF) was shown to have an initial reactive hyperemia that was followed, within the first hour, by persistent hypoperfusion (Part I). Intracranial pressure (ICP) was never elevated during the period of poor reperfusion. These experiments attempted to reverse the state of subnormal LCBF by inducing hypercarbia or hyocarbia or maintaining normocarbia. Although hypocarbia did increase LCBF at several electrode sites, neither the intracerebral steal syndrome nor the "squeeze" syndrome are a dominant consequence of hypercarbia in this model of global ischemia. Hypercarbia was consistently more effective in elevating LCBFs and in recovery of the electrocorticogram. It appears that, in the absence of raised ICP, hypercarbia may be preferred to normal or low PACO2,. Even though hypercarbia was superior to normocarbia or hypocarbia, hypercarbia was not a completely satisfactory regimen for reversing the state of poor reperfusion.

Normal human sleep: regional cerebral hemodynamics

Measurements of regional cerebral blood flow (rCBF) by the xenon 133 inhalation method along with polygraph recordings were made serially during relaxed wakefulness and different stages of nocturnal sleep in 18 right-handed normal volunteers. During stage I-II sleep the fast flow (Fg) values declined significantly, more in the brainstem-cerebellar (BSC) regions than in hemispheric regions. During stage III-IV sleep, Fg further declined diffusely in both hemispheric (-28%) and BSC (-29%) regions. During awakening from stage IV sleep to alpha-frequency wakefulness, BSC flow values increased more than hemispheric flow values. During REM sleep, regional Fg values increased diffusely in both hemispheric (+41%) and BSC (+47%) regions compared with wakefulness. There was a significant inverse correlation between the increase in end-tidal partial pressure for carbon dioxide and the reduction in bihemispheric Fg during sleep. Cerebral vasomotor responsiveness to carbon dioxide is decreased during both REM and non-REM sleep.

Normal human aging and cerebral vasoconstrictive responses to hypocapnia

Cerebral vasoconstrictive capacitance was measured during voluntary hyperventilation hypocapnia in 22 healthly normal volunteers aged 21--65 years by serial 133Xe inhalation estimates of rCBF by the initial slope index method of Risberg (ISI2) in the steady state followed by the hypocapnic state. End-tidal PCO2 was monitored by a capnograph. There was significant linear correlation between reduction of PECO2 and the ISI2 values. Significant reduction of cerebral vasoconstrictive response to hypocapnia was found with normal advancing age which is attributed to (1) minor atherosclerosis or loss of elasticity of cerebral vessels with advancing age, (2) the presence of an ischemic threshold during hyperventilation at which CBF tends to stabilize.

Correlation between dominant EEG frequency, cerebral oxygen uptake and blood flow

In 32 chronic patients the EEG in temporal and occipito-parietal bipolar leads was analyzed with a manual method giving a period frequency index. The cerebral oxygen uptake (CMRO2) was calculated from the arteriovenous oxygen difference between samples from the internal carotid artery and the jugular bulb respectively, and from measurement of cerebral blood flow with the 133Xenon clearance method. A strong correlation (r = 0.78, P less than 0.001) was found between the EEG frequency indices and the CMRO2 of the hemisphere from which the EEG was recorded. Significant correlations between the EEG indices and gray matter cerebral blood flow were also demonstrated, while the correlation between the EEG indices and the blood flow of the white matter was weak. No correlation at all was found between the EEG indices and the relative weight of the gray matter. We conclude that the EEG carries information about the metabolic activity of the brain tissue. The EEG frequency also correlates with the blood flow of the gray matter of the brain when tissue anoxia has not uncoupled the normal function--flow relationship prevailing in the brain.