Structural changes in the tissues of white rats after capsaicin administration

Attitudes to health and illness may differ between rural and urban dwellers. Issues that may relate to the provision of health services to rural dwellers are raised for consideration. The response of urban dwellers to illness or disability has often been linked to discomfort caused by pain or cosmetic attractiveness, while for rural dwellers the response to illness or disability is often related to the degree to which the illness or disability affects productivity. Often the rural resident will postpone seeking medical or associated services until it is economically or socially convenient. The notion of exposing their private lives to strangers or acquaintances from the local based services or to undertake the journey to distant services where the cultural or behavioural differences could be misunderstood, may impact on rural dwellers' well-being. Health service providers in rural areas need to understand such differences and difficulties when offering services.     

Early administration of intrapleural streptokinase in the treatment of multiloculated pleural effusions and pleural empyemas

In the treatment of multiloculated pleural effusions and empyemas tube thoracostomy often fails and more aggressive surgical therapy is required. Intrapleural administration of fibrinolytics is a valuable alternative. Between October 1994 and December 1995 28 patients (aged 22 to 62 years) with multiloculated pleural effusions were treated with intrapleural instillations of streptokinase after unsuccessful conventional chest tube drainage. Twenty-three pleural effusions were grossly purulent, others were loculated effusions with low pH. The most common cause of the pleural effusions was pneumonia. Duration of illness before hospitalization was 3 to 105 (mean 21.8) days. Treatment with streptokinase was started most commonly one day after chest tube placement. Once a day after clamping the chest tube streptokinase was administered intrapleurally for 10-15 minutes as a solution of 250,000 units in 100 ml normal saline. The tube remained clamped for 3 hours. Two to 8 (mean 3.7) instillations per patient were needed. Twenty-one cases (72.4%) showed excellent resolution of pleural effusion and needed no more therapy. However, one patient died in hospital due to purulent meningitis and bilateral pneumonia. Eight patients needed further surgical treatment, e.g. decortication, in 5 cases together with wedge lung resection. Eleven patients experienced some adverse effects of streptokinase therapy, most frequently chest pain and elevation of body temperature in one case pleural effusion became hemorrhagic, and one patient had nasal bleeding. We conclude that usage of intrapleural streptokinase in the treatment of multiloculated pleural effusions (including pleural empyemas) reduces the need for major surgical interventions in quite a large group of patients.     

Ontogeny of striatal dopamine release in rats after acute administration of methamphetamine

In the present study, we examined the effects of acute MAP administration on striatal extracellular levels of dopamine (DA) and its metabolites in groups of rats on postnatal days (PNDs) 14, 21, 28, and 56. A single injection of 4 mg/kg MAP (IP) induced increase in extracellular DA and decrease in extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatal perfusates of rats on all PNDs examined. The magnitude of increase in DA concentrations at 20 min after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56, whereas the magnitude of decrease in DOPAC concentrations after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56. After the MAP injection, homovanillic acid levels decreased on PNDs 21, 28, and 56, but increased on PND 14. These results suggest that rats on PND 14 differ from those thereafter in MAP-induced DA release and changes in its metabolites, and that such developmental effect on MAP-induced DA release may be involved in the ontogeny of MAP-induced behavioral sensitization.     

Systemic administration of kainate induces marked increases of endogenous kynurenic acid in various brain regions and plasma of rats

The endogenous neuroinhibitory and neuroprotective excitatory amino acid receptor antagonist kynurenic acid has been hypothetically linked to the pathogenesis of epilepsy and several other brain disorders. In the present study, alterations in kynurenic acid levels were examined in the kainate model of temporal lobe epilepsy. Kainate was systemically injected in rats at a dose (10 mg/kg s.c.) which induces a characteristic behavioural syndrome with stereotypies and focal (limbic) and generalized seizures, eventually progressing into severe status epilepticus. Kynurenic acid was determined 3 h after kainate injection in various brain regions (olfactory bulb, frontal cortex, piriform cortex, amygdala, hippocampus, nucleus accumbens, caudate/putamen, thalamus, superior and inferior colliculus, pons and medulla, and cerebellar cortex) and in plasma, using a sensitive high-performance liquid chromatographic method. When data were analysed irrespective of individual seizure severity, significant increases in kynurenic acid were determined in all brain regions examined except the hippocampus, nucleus accumbens and pons/medulla. The most marked (200-500%) increases above controls were seen in the piriform cortex, amygdala, and cerebellar cortex. Furthermore, a significant kynurenic acid increase of about 200% above control was determined in plasma. When kynurenic acid levels were determined in subgroups of rats with different behavioural alterations in response to kainate, the most marked kynurenic acid increases were seen in subgroups with status epilepticus. Rats which only developed mild (focal) seizures or stereotyped behaviours (wet dog shakes) also exhibited significantly increased kynurenic acid levels, thus indicating that the increase in kynurenic acid in response to kainate was not solely due to sustained convulsive seizure activity. Whereas it was previously proposed that kynurenic acid is involved only in later stages of seizure disorders, the present data demonstrate that marked increases in central and peripheral kynurenic acid levels occur early after the onset of neuroexcitation, at least in the kainate model.     

Systemic reactions in rats following the initiation of a local inflammatory process by subcutaneous administration of spirits of turpentine

Local inflammation was induced in rats by single (1 x 4 ml/kg) or multiple (14 X 0.2 ml/animal) infections of turpentine. The induction of inflammatory processes in both groups resulted in anemia and granulocytosis following an initial leukopenia. Thrombopenia on the second day, followed by thrombocytosis, was also observed in both groups. Studies on blood chemistry parameters revealed a decline in serum albumin; elevation of alkaline phosphatase in serum was observed only after multiple injection of turpentine. In these animals an elevation in the weights of spleen and adrenals and a reduction in the weight of thymus were also found.     

Excretion of Dische positive compounds in rats after irradiation and after administration of some cytostatic drugs

In order to verify some pathophysiological aspects in radio- and chemotherapy of tumors the excretion of Dische positive compounds in rats was followed. During fractionated whole-body irradiation of animals it was found that up to the exposure with 50 R/day the organism is able to repair the disturbances provoked by irradiation for a certain time and that within the course of irradiation a permanently higher excretion of Dische positive compounds occurs. On the contrary, following the exposure of 100 R/day after a short increase continual decrease occurs lasting until the death of the animal. The excretion of Dische positive compounds in rats was followed also after the application of Cyclophosphamide, cis-dichlorodiammineplatinum (II) and Vinblastine. All these three cytostatic drugs produce an increased excretion of Dische positive compounds on the first day after the application. In the case of Cyclophosphamide, it was demonstrated that the excreted amount of Dische positive compounds was dose dependent.     

Ultrastructure of B-cells of Langerhans islets in rats after the administration of L-leucine

Six women aged 31 to 70 years had folate deficiency and neuropsychiatric disorders. The three with acquired folate deficiency were depressed and had permanent muscular and intellectual fatigue, mild symptoms of restless legs, depressed ankle jerks, diminution of vibration sensation in the legs, stocking-type hypoesthesia and long-lasting constipation; D-xylos absorption was abnormal. The bone marrow was megaloblastic in only one patient, and she and one other had atrophy of the jejunal mucosa. The third was a vegan. All three recovered after folic acid therapy. The other three were members of a family with the restless legs syndrome, fatigability and diffuse muscular pain. One also had subacute combined degeneration of the spinal cord and kidney disease but no megaloblastosis; she improved spectacularly after receiving large daily doses of folic acid. The other two also had minor neurologic signs, controlled with 5 to 10 mg of folic acid daily. Unrecognized and treatable folate deficiency (with low serum folic acid values but normal erythrocyte folate values) may be the basis of a well defined syndrome of neurologic, psychiatric and gastroenterologic disorders, and the restless legs syndrome may represent the main clinical expression of acquired and familial (or inborn) folate deficiency in adults.     

Restoration of Leydig cells after repeated administration of ethane dimethanesulfonate in adult rats

Adult male rats were repeatedly treated with ethane dimethanesulfonate (EDS), an agent known to destroy Leydig cells selectively. Following a second injection, changes in serum testosterone levels and histological and morphometric changes of Leydig cells showed the time course to be similar to those after the first treatment. The number and volume of Leydig cells markedly decreased at day 2, began to increase from day 7, and recovered to the values of the control rats at day 30, concomitant with the changes of serum testosterone levels. Cells in the interstitial tissue labeled with bromodeoxyuridine markedly increased in number at day 2, gradually decreased thereafter, and returned to the values of the controls at day 14. During this period, cells undergoing mitosis were seen, their type unable to be determined, but were presumed to be regenerating Leydig cells. Even 30 days following four treatments with intervals of 30 days each, serum testosterone levels were the same as those in the controls. Also the numerical and volume densities of Leydig cells and the volume of an average Leydig cell were the same as those of the controls. Mitosis was observed in mature Leydig cells at this period, if any. It appears that new Leydig cells began to proliferate by division earlier than 14 days after EDS, allowing that there were several stages of proliferation, and that the source of reappearing Leydig cells may not be a limited number of precursor cells, implying the presence of stem cells for Leydig cells.     

Serum and urinary boron levels in rats after single administration of sodium tetraborate

The pharmacokinetics of boron was studied in rats by administering a 1 ml oral dose of sodium tetraborate solution to several groups of rats (n=20) at eleven different dose levels ranging from 0 to 0.4 mg/100 g body weight as boron. Twenty-four-hour urine samples were collected after boron administration. After 24 h the average urinary recovery rate for this element was 99.6+/-7.9. The relationship between boron dose and excretion was linear (r=0.999) with a regression coefficient of 0.954. This result suggests that the oral bioavailability (F) of boron was complete. Another group of rats (n=10) was given a single oral injection of 2 ml of sodium tetraborate solution containing 0.4 mg of boron/100 g body wt. The serum decay of boron was followed and found to be monophasic. The data were interpreted according to a one-compartment open model. The appropriate pharmacokinetic parameters were estimated as follows: absorption half-life, t1/2a=0.608+/-0.432 h; elimination half-life, t1/2=4.64+/-1.19 h; volume of distribution, Vd = 142.0+/-30.2 ml/100 g body wt.; total clearance, Ctot=0.359+/-0.0285 ml/min per 100 g body wt. The maximum boron concentration in serum after administration (Cmax) was 2.13+/-0.270 mg/l, and the time needed to reach this maximum concentration (Tmax) was 1.76+/-0.887 h. Our results suggest that orally administered boric acid is rapidly and completely absorbed from the gastrointestinal tract into the blood stream. Boric acid in the intravascular space does not have a strong affinity to serum proteins, and rapidly diffuses to the extravascular space in proportion to blood flow without massive accumulation or binding in tissues. The main route of boron excretion from the body is via glomerular filtration. It may be inferred that there is partial tubular resorption at low plasma levels. The animal model is proposed as a useful tool to approach the problem of environmental or industrial exposure to boron or in cases of accidental acute boron intoxication.     

Morphological and morphometric investigation of cardiac lesions after chronic administration of methamphetamine in rats

Neuroendocrine response to stress stimuli is aimed to maintain body homeostasis. The activation of the neuroendocrine system is accomplished mainly by two ways: by feedback regulation based on the recognition of altered metabolic homeostasis by appropriate receptors sending the signal into the CNS, and by forward regulation involving a direct stimulation of the neuroendocrine system by a central command coming from an activated brain regulatory center. With regard to mechanisms of neuroendocrine activation, the signal specificity and site of its origin are of particular importance. The significance of the signal in neuroendocrine responses has been evaluated in three different stress conditions: hypoglycemia, surgical trauma and dynamic physical exercise. The stimulus inducing neuroendocrine response during hypoglycemia is the glucopenia. The signal for the activation of the neuroendocrine response is generated in glucosensitive cells which are not located in a single brain structure (hypothetical glucostat). The signal for growth hormone, vasopressin and oxytocin release is produced in brain structures protected by the blood-brain barrier, that for ACTH release in regions both protected and unprotected by the barrier, while the signal for prolactin release is generated in tissues lacking the blood-brain barrier. The neuroendocrine response during surgical trauma is activated by a signal formed in the damaged tissue reaching the CNS by neural pathways. Moreover, cytokins may participate on endocrine stimulation in those surgical interventions in which a large amount of bacterial endotoxins is released. During a complicated surgery, e.g. during a bypass other signals and modifying factors, such as hypothermia, dilution of blood, hypoperfusion of organs, rewarming of the body and hormone degradation in the oxygenator are important. On the On the other hand, during a short-term dynamic exercise, a forward regulation by a central signal from the activated CNS motor center comes into play with the consequent release of catecholamines, growth hormone, etc. In the control of some other hormones (beta-endorphin, partly ACTH) and especially during a long term exercise, neural signals from working muscles (feedback) are also involved. During a static exercise mainly catecholamines triggered by signals from working muscle cells are activated. The understanding of the signal and mechanisms of neuroendocrine activation during stress is indispensable for selective modulation of physiological and pathological responses.     

Role of renal gluconeogenesis in the maintenance of glycaemia after L-tryptophan administration to rats

The time-course of liver and kidney gluconeogenesis after L-tryptophan administration has been studied. Two and half hours after injection of L-tryptophan (0.5 g/kg body wt) a 97% inhibition of hepatic gluconeogenesis in starved rats was observed. Twelve hours later, the inhibition remained 35%. Hepatic glycogen was almost completely depleted (97%) in fed rats after 5 hours. At this time there was a severe hypoglycaemia in fed and 48 h starved rats which gradually disappeared with time, the values going back to normal after 12 hours. Tryptophan treatment was associated with a significant increase in renal gluconeogenesis in fed and 48 h starved rats with a maximum at 5 h (165% and 190% respectively). When hepatic gluconeogenesis was constantly inhibited in fed rats by periodic injection (every 4 h) of L-tryptophan, renal gluconeogenic ability remained increased throughout the experiment while blood glucose concentrations did not change. These observations suggest that kidney contributes to maintain glycaemic homeostasis under these conditions of liver gluconeogenesis impairment.     

Systemic methotrexate toxicity. A pharmacological study of its occurrence after intrathecal administration in a patient with renal failure

Methotrexate pharmacokinetic studies, performed on a patient with renal impairment who had toxic effects following 20 mg/sq m of intrathecally administered methotrexate, demonstrated prolonged serum concentrations of the drug, which accounted for the condition. After the return of normal renal function, pharmacokinetic studies were repeated following the same dose and route of administration of methotrexate. On this occasion there was a rapid clearance of serum methotrexate below toxic levels.     

The longitudinal distribution of cadmium, zinc, copper, iron, and metallothionein in the small-intestinal mucosa of rats after administration of cadmium chloride

Different routes of Cd intake may influence the intestinal distribution of Cd, metallothionein (MT), and trace metals differently. Therefore, we compared the effects of parenteral and enteral administration of Cd on the distribution of trace metals and MT along the small intestine. In a first experiment three groups of rats were employed: a control, one receiving CdCl2 within the drinking water, and another receiving sc injections of CdCl2. In a second experiment, rats were fed three different diets with either 0, 0.3, or 1 mmol CdCl2/kg for one and two weeks to study the time- and dose-dependent effects of orally administered Cd. Metal concentrations (Cd, Zn, Cu, Fe) were measured by atomic emission spectrometry and MT was determined by radioimmunoassay. Intestinal MT levels did not show proximodistal gradients in controls or after sc administration of Cd, but orally administered Cd increased mucosal MT levels longitudinally from the duodenum to the ileum. Cd levels paralleled those of MT. Compared with the metal concentrations in the controls, sc administration of Cd did not change intestinal Zn, Cu, and Fe levels. Oral administration of Cd, however, increased Cu and decreased Fe levels in the intestinal mucosa significantly. The second experiment revealed that only high dietary concentrations of Cd increase intestinal Cd and MT levels longitudinally toward the distal parts, whereas at lower dietary concentration the longitudinal distribution was reversed. This shows that different routes and doses of Cd intake lead to a different trace metal and MT distribution and emphasizes the role of dietary Cd in the local induction of small-intestinal MT.     

Preventive administration of ornithine alpha-ketoglutarate improves intestinal mucosal repair after transient ischemia in rats

Introduction; Healthcare professionals need to continually update their knowledge to provide care based on scientific evidence. In some cases it can be difficult to gain access to the different sources of medical information. In an attempt to overcome these problems, a toll-free telephone medical information service (Doctorline) was established. OBJECTIVE: To describe the development, aims, organization, and activities of this private service. METHODS: Doctorline is an independent, unbiased, toll-free medical information service that provides information on clinical, pharmacologic, and toxicologic issues; bibliographic searches; full-text articles; public and private clinics; details of forthcoming congresses; and legislative documentation. The service is available Monday through Friday, 1000 to 2000. Staff members are physicians trained in communication techniques, literature evaluation methodologies, and computerized database use. The main on-line facilities are MEDLINE, Micromedex-CCIS, and the Italian Formulary on CD-ROM. Books, bulletins, national and international drug formularies, and property files (i.e., directory of Italian public and private clinics) are also available. RESULTS: In 5 years, Doctorline has received 65 258 calls. Nearly 34% of the calls were made by general practitioners, followed by cardiologists (22%), orthopedists (15%), pharmacists (14%), gastroenterologists (13%), and urologists (10%). From 1991 to 1996, nearly 20% of the calls concerned pharmacologic issues, 43% nonpharmacologic issues, while the rest of the calls were for nonclinical requests. Approximately 21% of all questions received an answer during the same phone call (on-line answers); for the other answers (off-line answers) the mean +/- SD waiting time was 7.8 +/- 10.4 days. Although the nature of the questions has been recorded since 1991, data about the exact number of physicians who used the service are available only from 1994. Data from 1994 indicate that of the 52,181 physicians who could access the service, only 8817 (16.9%) called at least once, with a mean number of calls per physician of 3.9 (range 3.0-5.6). CONCLUSIONS: The future of Doctorline will depend on the quality and validity of the information provided (i.e., based exclusively on scientific evidence, independent of the source of funds), the promotion of the aims, organization, and clinical utility of the service (especially among physicians who made little or no use of the service), and differentiation of the service activities in relation to the physician's specific needs.     

Anatomic distribution of anesthetic solutions in the orbit after subconjuctival, parabulbar and retrobulbar administration

BACKGROUND: Given the therapeutic potential of proton pump inhibitor-based triple therapy for successful cure of Helicobacter pylori infection, we evaluated the efficacy and safety of lansoprazole with clarithromycin and amoxicillin in an open-label, single-center study. MATERIALS AND METHODS: H. pylori-positive patients self-administered lansoprazole, 30 mg; clarithromycin, 500 mg; and amoxicillin, 1 gm bid for 14 days. Patients were assessed pretreatment, at which time the presence of H. pylori was documented by rapid urease test, culture, or histology, following study drug administration (week 2) for a brief evaluation only, and at least 4 weeks posttreatment (week 6), which included endoscopy with collection of biopsy specimens for culture and histology testing. RESULTS: Primary clarithromycin and metronidazole resistance were observed in 6% (2 of 30) and 43% (13 of 30) of study patients, respectively. One month after the end of therapy, H. pylori infection was cured in 23 of 25 patients (92%; 95% confidence interval, 74%-99%). The triple-therapy regimen was well-tolerated; 17% of patients (5 of 30) reported mild to moderate adverse effects during the treatment period. CONCLUSION: A 2-week, triple-drug combination of lansoprazole, clarithoromycin, and amoxicillin is highly effective for cure of H. pylori infection. Additionally, the triple-drug combination was well-tolerated by patients infected with H. pylori.     

Effect of glucose administration on contusion volume after moderate cortical impact injury in rats

Previous studies had shown that pre- and postinjury glucose administration increased brain injury caused by a mild cortical impact injury only when the traumatic injury was complicated by a secondary ischemic insult. The purpose of this study was to examine the effect of pre- and postinjury glucose administration on a more severe cortical impact injury, where primary ischemia occurs at the site of the impact. Long Evans rats who were fasted overnight and anesthetized with isoflurane were subjected to a 5-m/sec, 2.5-mm impact injury. The animals were randomly assigned one of the following treatments: (1) 2.2 g/kg glucose in 4 ml of saline, 20 min prior to injury; (2) 2.0 g/kg glucose in 4 ml of saline, 20 min after injury; or (3) 4 ml of saline either 20 min before injury or 20 min after the injury. At 2 weeks, the animals were sacrificed and the brains were examined for contusion volume and for neuronal loss in CA1 and CA3 regions of the hippocampus. Contusion volume was increased from a median value of 23 mm3 in the saline-infused animals to 34 mm3 in the preimpact glucose infusion animals (p=0.005). Postimpact glucose infusion had no effect on contusion volume. Neuron density in CA1 and CA3 regions of the hippocampus was similar in all three treatment groups. These studies support the hypothesis that glucose administration adversely affects experimental traumatic brain injury in those circumstances where the trauma is complicated by primary cerebral ischemia, such as around cortical contusions.     

Gender differences in N-alkyl protoporphyrin IX production in rats after the administration of porphyrinogenic xenobiotics

OBJECTIVE: To study the effect of an educational intervention on the management of hospitalized infants with bronchiolitis. DESIGN: Sequential, prospective cohort study. SETTING: A 235-bed children's hospital with nearly all private rooms. PATIENTS: Consecutively admitted, previously healthy children younger than 24 months with symptoms of bronchiolitis. The first cohort was enrolled between January 1 and January 21, 1996; the second cohort between January 29 and February 18, 1996, following a 1-week intervention period; the third (follow-up) cohort between December 1996 and February 1997. INTERVENTION: Educational program and practice guidelines aimed at appropriate utilization of diagnostic tests, decreased antibiotic and bronchodilator use, increased compliance with isolation, decreased length of stay, and maintenance of quality care. MAIN OUTCOME MEASURES: Utilization of respiratory syncytial virus (RSV) enzyme immunoassay, initiation and duration of parenteral antibiotic therapy, number of nebulized bronchodilator treatments, isolation orders, length of stay, and readmission rate. RESULTS: A total of 90 patients were studied preintervention, 63 postintervention, and 90 during the follow-up period. The groups were comparable in demographic and clinical features. No patient had a documented serious bacterial infection; however, almost half in each group received parenteral antibiotics, despite recommendations against this. Immediately postintervention, children with positive RSV test results received antibiotics on fewer days than other children (median 0.6 vs 2.4 days; P=.004), suggesting that physicians stopped treatment with antibiotics once a viral diagnosis was confirmed. This effect did not persist into the follow-up period. Viral testing was reduced and isolation orders increased. Use of bronchodilators was reduced from 91% preintervention to 80% during the follow-up period (P=.046), and the median number of treatments was reduced from 15.0 to 10.0 (P=.005). There was no change in length of stay, which was 2 to 3 days, or in readmission rate, which was 1% to 4%. CONCLUSION: Educational efforts centered around practice guidelines can improve some aspects of the treatment of patients hospitalized with bronchiolitis.     

Pharmacokinetics of acetaminophen after intravenous and oral administration to spontaneously hypertensive rats and normotensive Wistar rats

In our previous study, we reported the faster metabolism of intravenously administered furosemide, hence the smaller diuretic effect of furosemide in spontaneously hypertensive rats (SHRs) of 16 weeks of age than in the age-matched normotensive Wistar rats. In present study, in order to evaluate whether there is some alteration of the phase II metabolism including glucuronide and sulfate conjugations in 16-week-old SHRs and the age-matched Wistar rats, the pharmacokinetic parameters of acetaminophen (A), A-sulfate, and A-glucuronide were investigated after intravenous (iv) and oral 100 mg/kg administration of A to 16-week-old SHRs and the age-matched Wistar rats. After iv administration of A, the mean fraction of iv dose excreted in 24-h urine as A-sulfate (75.6 versus 67.8%) and the partial clearance of A to A-sulfate (8.10 versus 6.89 mL/ min/kg) were significantly greater in SHRs than in Wistar rats. Conversely, the mean fraction of iv dose excreted in 24-h urine as A-glucuronide (9.39 versus 15.0%) and the partial clearance of A to A-glucuronide (1.01 versus 1.49 mL/min/kg) were significantly smaller in these SHRs. Similar results were also obtained after oral dosing of A. The in vitro sulfotransferase activity toward A was significantly smaller (0.397 versus 0.331 microg/min/mg of protein) in 16-week-old SHRs than in the age-matched Wistar rats, whereas, the glucuronyltransferase activity toward A was not significantly different between these SHRs and Wistar rats. On the other hand, there was no significant difference in the both sulfotransferase and glucuronyltransferase activity toward A between 6-week-old SHRs and age-matched Wistar rats. Therefore, the alterations in sulfation and perhaps glucuronidation of A between 16 -week-old SHRs and normotensive Wistar rats suggested that some physiological factors derived from the chronic hypertensive status in SHRs might affect the disposition of drugs.     

Systemic hemodynamics during hyperbaric oxygen exposure in rats

The effect of 1-5 bar O2 on left ventricular pressure (LVP), maximal velocity of LVP rise (+dP/dt) and fall (-dP/dt), systolic arterial pressure (APsys), pulse pressure (delta AP), heart rate (HR), and respiratory frequency (RF) was studied in anesthetized and conscious rats. At 1 bar O2, all blood pressure parameters increased significantly (9-56%) in both groups of rats, while RF fell (11-12%). HR fell only in conscious rats, while arrhythmias occurred in both groups. Compression to 5 bar O2 induced a significant further increase in all blood pressure parameters. HR fell further in the conscious rats. Arrhythmias were observed in increasing number during compression and at 5 bar O2. Elevation in estimated oxygen-consumption of the heart was found both during compression and at 5 bar O2. We conclude that O2 exposure markedly stimulates the myocardium by elevating the LVP, +dP/dt, and -dP/dt, thus elevating APsys and delta AP. Arrhythmias developed in both groups, while bradycardia occurred only in conscious rats.