Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CONSCIOUSNESS”

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.

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

At least 1,387 records · Page 77Linked to original sources
PubMed2002

ATP-sensitive potassium channels do not have a main role in mediating late preconditioning protection against arrhythmias and stunning in conscious sheep.

OBJECTIVE: Although late preconditioning protects against stunning following several short periods of ischemia-reperfusion, it is not clear if it confers protection against stunning and malignant arrhythmias after a sustained reversible ischemia, and whether KATP channels are involved as triggers and/or end effectors of the protective mechanism. The purpose of this work was thus to test these issues in conscious sheep. METHODS: Five groups were considered: CONT (control): the animals were submitted to 12 min ischemia followed by 2 h reperfusion; SWOP (late preconditioning): on the first day, the animals were preconditioned with 6 periods of 5 min ischemia 5 min reperfusion and 24 h later they were submitted to 12 min ischemia followed by 2 h reperfusion; GLIB: same as CONT with the KATP channel inhibitor glibenclamide (0.4 mg/kg) infused 30 min prior to the 12 min ischemia; SWOPG2: same as SWOP with glibenclamide before the 12 min ischemia; SWOPG1: same as SWOP with glibenclamide prior to the preconditioning stimulus. RESULTS: Percent reperfusion recovery of wall thickening fraction (% WTh) showed late preconditioning protection against stunning throughout reperfusion (SWOP vs CONT, p < 0.01). Arrhythmia severity index (ASI) also demonstrated that late preconditioning protects against malignant arrhythmias at the onset of reperfusion (CONT: 4.87 +/- 1.62 vs SWOP: 1.39 +/- 0.93, p < 0.01). Glibenclamide was unable to prevent preconditioning, both against stunning and arrhythmia incidence, when administered either before the preconditioning stimulus (SWOPG1 vs CONT, p < 0.01) or before the sustained ischemia (SWOPG2 vs GLI, p < 0.01). CONCLUSIONS: Results indicate that late preconditioning protects against stunning and arrhythmias following a reversible, sustained ischemia in conscious sheep and that KATP channel participation is negligible as triggers and end effectors of both types of protection.

Action Potentials↗
PubMed1986

Facilitation of lethal ventricular arrhythmias by therapeutic digoxin in conscious post infarction dogs.

The proarrhythmic potential of digoxin, administered in a therapeutic dosage regimen, was evaluated in conscious dogs in the subacute phase of myocardial infarction. In this evaluation, digoxin (0.0125 mg/kg/day intravenously) or vehicle were administered to conscious dogs for periods of 5 to 7 days, commencing 4 to 5 days after anterior myocardial infarction. Before treatment, programmed ventricular stimulation failed to initiate ventricular tachycardia in 26 post infarction dogs. After treatment, programmed stimulation initiated ventricular tachyarrhythmias in only 1 of 13 digoxin-treated dogs (1.36 +/- 0.17 ng/ml serum digoxin) and in 0 of 13 vehicle-treated dogs. However, the incidences of early ventricular fibrilation (4 of 10 digoxin vs 0 of 12 vehicle; p less than 0.05) and of 24-hour mortality (6 of 10 digoxin vs 2 of 12 vehicle; p less than 0.05) occurring in response to the development of posterolateral ischemia in the presence of previous anterior myocardial infarction was significantly greater in digoxin-treated (1.47 +/- 0.19 ng/ml serum digoxin) than in vehicle-treated animals. These findings suggest an enhanced susceptibility toward the development of ischemia-related lethal arrhythmias in the presence of therapeutic digoxin serum concentrations early after myocardial infarction, which is not predicted by programmed ventricular stimulation testing.

Animals↗
PubMed1988

Spatial and temporal characteristics of circumferential flow-function relations during acute myocardial ischemia in the conscious dog.

In the anesthetized open-chest dog the ischemic area produced by coronary occlusion is surrounded by an area of nonischemic contractile dysfunction, identified as the functional border zone. To establish whether a similar functional border zone exists in the conscious animal during acute regional ischemia and to determine its spatial dimensions and temporal changes, we performed simultaneous two-dimensional echocardiography and radioactive microsphere studies in nine chronically instrumented dogs. We produced circumferential flow-function maps at 22.5-degree intervals over the full circumference of the left ventricle at the midpapillary muscle level during control conditions, 5 minutes after left circumflex occlusion, and 2.5 hours after left circumflex occlusion. After occlusion there was no change in left ventricular end-diastolic area, an increase in left ventricular end-systolic area (p less than 0.01), and a decrease in left ventricular area ejection fraction (p less than 0.01). The circumferential extent of left ventricular dysfunction was 197 +/- 11 degrees (mean +/- SEM) at 5 minutes of left circumflex occlusion, whereas the extent of subendocardial hypoperfusion was 144 +/- 6 degrees (p less than 0.0005). This produced a functional border zone measuring 54 +/- 8 degrees, or 25% of the nonischemic myocardium, which did not change over the 2.5-hour occlusion period. Despite a modest but significant decrease in wall thickening (70 +/- 6% to 43 +/- 6%; p less than 0.01) in the functional border zone, there was no difference in subendocardial blood flow between the functional border zone and the control nonischemic area. We conclude that a discrete functional border zone exists in the conscious dog during acute regional ischemia produced by circumflex coronary occlusion, which does not change during the early evolution of myocardial infarction. The functional border zone likely contributes to minor overestimation of infarct size in the early hours after myocardial infarction if extent of left ventricular dysfunction is used as an index of infarction in humans.

Animals↗
PubMed1978

Pharyngeal aspiration in normal adults and patients with depressed consciousness.

A sensitive technic using indium111 chloride was devised to investigate the occurrence of pharyngeal aspiration. Twenty normal subjects and 10 patients with depressed consciousness were studied. Forty-five per cent of the normal subjects aspirated during deep sleep. Normal subjects who did not aspirate were noted to sleep poorly. Seventy per cent of the patients with depressed consciousness aspirated. Aspiration of pharyngeal secretions occurs frequently in patients with depressed sensorium and also in normal adults during deep sleep. Bacterial pneumonia may result when aspirated bacteria are not effectively cleared. This may result when clearance mechanisms are impaired or when they are overwhelmed by large volumes of aspirated secretions.

Adult↗
PubMed1995

Beyond determinism and materialism, or isn't it time we took consciousness seriously?

This essay argues: (1) that the fundamental conflict between the behaviorist and cognitive approaches to psychology are philosophical, not scientific; (2) that the philosophical premises underlying behaviorism (materialism, epiphenomenalism, functional model of causality, and the rejection of concepts referring to conscious states and processes) are false; and (3) that an objective, scientific approach to psychology must take consciousness and volition as axiomatic starting points.

Cognition↗
PubMed1993

Calcium-mediated metabolic stimulation of neuroendocrine structures by intraventricular endothelin-1 in conscious rats.

We examined the hypothesis that the vascular- and brain-derived peptide, endothelin-1 (ET), would affect cerebral neuroendocrine structures when administered via the peripheral circulation or via a lateral cerebral ventricle (i.c.v.). ET was infused intravenously (14 nmol/min) or injected i.c.v. (9 pmol) in conscious rats in which local cerebral glucose metabolism was assessed by the quantitative autoradiographic [14C]deoxyglucose technique. Whereas intravenously infused ET was previously demonstrated to selectively stimulate metabolic activity in the pituitary intermediate and anterior lobes of conscious rats, it was without effect in 20 individual structures or subnuclei involved in neuroendocrine functions, including several circumventricular organs. Intraventricular ET, however, caused hypermetabolic responses in 9 neuroendocrine structures, including the pineal gland, subfornical organ, median eminence, the hypothalamic paraventricular and supraoptic nuclei, and other hypothalamic and preoptic structures. The metabolic stimulation resulting from central ET was abolished or attenuated regionally by i.c.v. pretreatment with the calcium L-channel inhibitor, nimodipine. The findings indicate that i.c.v. ET elicits a calcium-mediated hypermetabolic effect on several neuroendocrine structures in the forebrain involved in the regulation of fluid homeostasis, the cardiovascular system, and body temperature.

Animals↗
PubMed1995

Cardiovascular effects elicited by central administration of physostigmine via M2 muscarinic receptors in conscious cats.

The cardiovascular effects of an intracerebroventricular (i.c.v.) injection of physostigmine were studied using conscious cats. Physostigmine (5-25 micrograms: 5 microliters) caused a dose-dependent increase in mean arterial pressure (MAP) and heart rate (HR). The highest dose (25 micrograms) increased MAP and HR by 32 +/- 3 mmHg and 45 +/- 5 beats/min, respectively (n = 5). Pre-administration of the muscarinic receptor antagonist, atropine (25 micrograms; i.c.v.) blocked the effects of physostigmine (25 micrograms; i.c.v.). Also, the pre-administration of the M2 muscarinic antagonist, methoctramine (25 micrograms; i.c.v.), antagonized the cardiovascular effects of physostigmine without altering the baseline variables. However, the M1 muscarinic antagonist, pirenzepine (100 micrograms; i.c.v.) did not alter baseline MAP or HR, and also failed to inhibit the cardiovascular responses to physostigmine. Similarly, the M3 muscarinic blocker, 4-diphenyl-acetoxy-N-methylpiperidine methiodide (50 micrograms; i.c.v.), neither changed baseline cardiovascular variables nor blocked the effects of physostigmine. When the same cats were anesthetized with intravenous injection of sodium pentobarbital (25-30 mg/kg), physostigmine (25 micrograms; i.c.v.) evoked a decrease in MAP and HR of 13 +/- 6 mmHg and 15 +/- 6 bpm, respectively (n = 5). These results demonstrate that the increases in MAP and HR to the i.c.v. administration of physostigmine in conscious cats are possibly mediated through stimulation of central M2 muscarinic receptors. In addition, anesthesia reverses the effects elicited by the central administration of physostigmine to a decrease in MAP and HR.

Animals↗
PubMed1995

New algorithmic-based digital filter processing system for real-time continuous blood pressure measurement and analysis in conscious rats.

A new algorithmic-based digital filter processing system for real-time continuous blood pressure (BP) measurement and analysis in freely-moving conscious rats has been developed. Real-time recognition of BP waveforms, real-time noise rejection and determination of representative waveform indexes (WIs) at indicated time points using digital filters and Smirnov's rejection test were realized with this system. Digital filters were applied for two different purposes: waveform segmentation and smoothing the calculations of representative WIs. Smirnov's rejection test was used for real-time noise rejection and yielded an accurate rejection rate of 99.99%. The result was that the digital filter processing and Smirnov's rejection test realized accurate real-time BP measurement and analysis in freely-moving conscious rats using a personal computer.

Algorithms↗
PubMed1991

HA1077, a novel calcium antagonistic antivasospasm drug, increases both cerebral blood flow and glucose metabolism in conscious rats.

The effects of a novel calcium antagonistic antivasospasm drug, HA1077, on local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were studied in 33 anatomically discrete regions of the brain in conscious rats, using the quantitative autoradiographic [14C]iodoantipyrine and [14C]2-deoxyglucose techniques. HA1077 was infused i.v. over a 30-min period (1 or 3 mg/kg). HA1077 significantly increased LCBF in 9 of 33 sites in rats given 1 mg/kg, and in 14 of 33 sites in rats given 3 mg/kg compared to the control group given vehicle. Significant increases in LCGU were also noted in 16 of 33 sites in rats given 3 mg/kg. HA1077 increased both cerebral blood flow and glucose metabolism in conscious rats.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Effect of cicletanine on overpacing-induced ST-segment elevation in conscious rabbits. A comparison with verapamil.

We compared the effects of cicletanine (10 mg/kg i.v.) and verapamil (0.1 mg/kg i.v.) on heart rate, ventricular effective refractory period, systolic and diastolic arterial blood pressure and overpacing-induced ST-segment elevation detected by right ventricular intracavital electrogram in conscious rabbits. Cicletanine significantly reduced overpacing-induced ST-segment elevation, which is an indicator of myocardial ischemia, and heart rate, but did not influence blood pressure and ventricular effective refractory period. Verapamil did not significantly influence ventricular effective refractory period, blood pressure or heart rate, but reduced the ST-segment elevation induced by frequency loading. These results suggest that acute treatment with cicletanine induces an anti-ischemic effect in the overpaced heart of conscious rabbits.

Animals↗
PubMed1989

Reperfusion-induced arrhythmias in the conscious rat: a comparative study with three calcium antagonists.

The effects of three calcium antagonists (diltiazem, verapamil, and nifedipine) on reperfusion-induced arrhythmias were compared in a conscious rat preparation with coronary artery occlusion and implanted electrocardiogram limb electrodes. Upon reperfusion after a 5-min period of occlusion, all (15/15) untreated control rats exhibited immediate ventricular tachycardia, which rapidly deteriorated to ventricular fibrillation; 87% (13/15) of the rats died as a consequence of these rhythm disturbances. In the groups treated with calcium antagonists, each drug (diltiazem, verapamil, or nifedipine) was given as an intravenous bolus 10 min prior to coronary occlusion (n = 12 in each group). The incidence of ventricular fibrillation was significantly reduced by all three calcium antagonists and this antifibrillatory effect resulted in a significantly lower mortality in all drug-treated groups. With diltiazem (0.5 and 2.0 mg/kg) mortality fell from 87 to 42% (P less than 0.05) and 35% (P less than 0.01), respectively; with verapamil (0.5 and 5.0 mg/kg) it fell to 25% (P less than 0.01) and 0% (P less than 0.001); and with nifedipine (5.0 and 50 micrograms/kg), it fell to 25% (P less than 0.01) and 8% (P less than 0.001). At a dose of 5.0 mg/kg, verapamil caused a large reduction in heart rate both prior to and during coronary occlusion and reperfusion; however, with other doses and drugs no significant changes in heart rate were observed. ST segment elevation during the 5-min ischemic period was reduced by pretreatment with all drugs. In conclusion, in the conscious rat, pretreatment with diltiazem, verapamil, or nifedipine affords some protection against reperfusion-induced arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Altered states of consciousness in disorders of daytime sleepiness.

Patients with daytime sleepiness present altered states of consciousness. The occurrence of these states impairs their professional, social and familial activities and may threaten life itself. The automatic behavior syndrome is characterized by continuation of mechanical activity and complete amnesia. Episodes lasting from a few seconds to several hours are correlated with repetitive micro-sleep periods. During cataplectic attacks, patients may have a meshing of reality with hallucinatory dream contents. Sleep-induced apnea may lead to abnormal movement and abnormal ambulation during sleep as well as hallucinations in the early morning. These altered states of consciousness must be considered as diagnostic indexes in differentiating epileptic syndromes from syndromes of daytime sleepiness.

Adult↗
PubMed1983

Ventilation during acute HCl infusion in intact and chemodenervated conscious rabbits.

The ventilatory response to acute (0-90 min) intravenous infusion of HCl was studied in awake, conscious rabbits with intact (CB+) and denervated (CB-) carotid bodies. The HCl dose was delivered such as to produce an increasing degree of acidosis over 90 min reaching blood pH values of 7.032-7.115 at 60-90 min and plasma [HCO-3] values of 8.5-10.6 mmol . L-1 . CB- rabbits exhibit an increase in VT by 7 min and a decrease in PaCO2 by 15 min of infusion, changes that increased over 90 min. However, at all times the CB- response was significantly less than that in CB+ rabbits. The relationships, percent decrease in PaCO2 vs delta [H+] and percent increase VT vs delta [H+], were well approximated by linear regression analysis in both CB+ and CB- groups and the slope, as an index of the response sensitivity, was, in CB- rabbits, 0.33-0.37 of that in CB+ rabbits. In the conscious, awake rabbit, peripheral chemoreceptors seem to account for up to 2/3 of the ventilatory response to metabolic acidosis.

Animals↗
PubMed1983

Effects of aspirin and indomethacin on cerebral circulation in the conscious rat: evidence for a physiological role of endogenous prostaglandins.

The purpose of this work was to evaluate the effects of equipotent doses of two different inhibitors of cyclo-oxygenase, indomethacin and aspirin, on cerebral blood flow and cerebral vascular resistances in the conscious undisturbed rat, using the reference sample radioactive microsphere method. We found that both, aspirin (50 mg/kg) and indomethacin (5 mg/kg) at 3, 15 and 60 min after their intravenous administration, increased cerebral vascular resistances and decreased cerebral blood flow to a similar extent. Both drugs completely abolished the hypotensive effect of 5 mg/kg i.v. arachidonic acid and they did not change arterial PO2, PCO2 or pH values. We conclude that the pharmacological inhibition of cyclooxygenase in the conscious undisturbed rat leads to a cerebral vasoconstriction and consequently to a decrease in cerebral blood flow. Our results evidence that prostaglandins are a physiological factor that actively contributes to the maintenance of cerebral circulation.

Animals↗
PubMed1982

A model for evaluation of postural hypotension induced by drugs in conscious restrained normotensive rats.

A rat model was developed for use in evaluating postural hypotensive activity of a compound. Conscious normotensive rats were restrained on a tilt board with special restrainers to avoid blocking limb circulation. Dose response curves were explored to delineate the potential postural hypotensive activity of a compound. In response to a 2-min 90 degree head-up tilt, only a negligible changes in blood pressure was observed in the control state. The conscious rat was therefore able instantaneously to compensate for postural change. This ability, however, was blocked by guanethidine. The compound induced a dose-related hypotension and a further, dose-dependent drop in blood pressure on tilt. Hydralazine, on the other hand, induced only dose-dependent hypotension, but no change in blood pressure response from control tilts. Since these findings appear to be in accord with human clinical data, this rat model may be suitable for use in evaluating potential postural hypotensive activity of compounds.

Anesthetics↗
PubMed1988

Changes in plasma catecholamines and plasma renin activity during hypotension in conscious rats with lesions of the nucleus tractus solitarii.

The purpose of the present study was to examine the effects of lesions of the nucleus tractus solitarii on the reflex control of sympathetic activity and renin release in the conscious rat. Two doses of the arteriolar vasodilator hydralazine (0.3 and 1 mg/kg, i.v.) were used to activate reflexively the sympathetic nervous system in nucleus tractus solitarii lesion and control rats. Administration of 1 mg/kg of hydralazine to the control rats caused mean arterial pressure to fall from 120 +/- 2 mm Hg to 84 +/- 2 mm Hg and elicited an 11.2-fold increase in plasma renin activity and a 2.7-fold increase in plasma norepinephrine concentration. Administration of 0.3 mg/kg of hydralazine caused the arterial pressure of the lesion group to fall from 118 +/- 3 mm Hg to a comparable value of 85 +/- 4 mmg Hg, but plasma renin activity and plasma norepinephrine concentration did not rise significantly. However, administration of 1 mg/kg of hydralazine to the lesion group caused arterial pressure to fall from 128 +/- 6 mm Hg to 64 +/- 2 mm Hg, in association with a 12.4-fold increase in plasma renin activity and a 1.6-fold elevation in plasma norepinephrine concentration. Atenolol, a beta 1-adrenoceptor antagonist, blocked 70% of the rise in plasma renin activity caused by 1 mg/kg of hydralazine in both groups of rats. In addition, prior renal denervation also markedly attenuated the rise in plasma renin activity caused by hydralazine in the lesion group. Finally, electrical stimulation of the vagus nerves, which caused a large vasodepressor response in the control group, failed to lower the arterial pressure of the lesion group. Based on these observations, we conclude that in the conscious rat (1) nucleus tractus solitarii lesions eliminate the arterial baroreflexes as well as the cardiopulmonary baroreflex, and (2) severe hypotension induces sympathetically mediated renin release in the apparent absence of arterial and cardiopulmonary baroreflex function.

Animals↗
PubMed1991

Neural control of urinary sodium excretion during hypertonic NaCl load in conscious rabbits: role of renal and hepatic nerves and baroreceptors.

We examined responses of renal nerve activity, urine flow, and urinary Na+ excretion to a hypertonic NaCl infusion in chronically instrumented conscious rabbits with unilateral renal denervation. The intravenous infusion of 20% NaCl, at 0.2 ml/min for 30 min, increased plasma osmolality by 27 +/- 5 mOsm/kg, and plasma Na+ by 16 +/- 3 mEq/l, and decreased hematocrit by 5 +/- 1%. These changes were accompanied by a marked decrease in renal nerve activity by 82 + 7%. Urine flow and urinary Na+ excretion increased gradually and peaked at the end of infusion. The innervated kidney excreted 23.3 +/- 3.3 ml urine and 5.5 +/- 0.7 mEq Na+ for the subsequent 60 min. However, the contralateral denervated kidney excreted only 9.5 +/- 2.0 ml urine and 2.2 +/- 0.6 mEq Na+; these values were significantly less than those of the innervated kidney. To examine the role of the sinoaortic and cardiopulmonary baroreceptors and the hepatic nerves in the response of renal nerve activity to the hypertonic NaCl infusion, renal nerve activity was examined in conscious rabbits with sinoaortic baroreceptor denervation (SAD) plus vagotomy and/or section of the anterior and posterior hepatic nerves (SAPH). In rabbits with SAD plus vagotomy or SAPH, the NaCl infusion also decreased renal nerve activity. After combining SAPH and SAD plus vagotomy, the decrease in renal nerve activity was completely blocked. These results indicate that hypertonic NaCl infusion elicits a marked decrease in renal nerve activity which is mediated predominantly by sinoaortic and cardiopulmonary baroreflexes and the hepatic nerves, and that the decrease in renal nerve activity plays an important role in the augmentation of renal function.

Afferent Pathways↗
PubMed1991

Does anesthesia cause loss of consciousness?

Although about 30 million operations carried out under general anesthetic are routinely performed each year in the USA alone, it is not possible to determine reliably whether or not a given anesthetized patient is conscious during surgery. As a result, some patients may be either partially aware during the operation or may be able to recall some aspects of it afterwards. It is therefore crucial to develop some experimental means to evaluate the state of consciousness of the anesthetized patient. Recent developments suggest that 40 Hz neuronal oscillations might help to solve this problem.

Anesthesia↗