Effects of buprenorphine on body temperature, locomotor activity and cardiovascular function when assessed by telemetric monitoring in rats.

Buprenorphine is a potent analgesic commonly used clinically in humans and rodents experiencing severe pain. However, effects of therapeutic doses on locomotor activity and the cardiovascular system have not been studied in conscious animals. The effects of buprenorphine were therefore evaluated in this study using telemetric monitoring in conscious animals. Telemetry transmitters were implanted in the peritoneal cavity of Wistar rats with a pressure catheter in the aorta and electrodes for electrocardiogram (ECG) recording subcutaneously. After a single subcutaneous administration of saline, each rat was administered single subcutaneous doses of 0.006, 0.03 or 0.15 mg/kg body weight (bw) of buprenorphine. During a 10 h period after administration, buprenorphine induced a varying dose-dependent increase in body temperature, heart rate, dP/dt and systolic-diastolic blood pressure, as well as a corresponding decrease in QT time. At high dose, however, QT time was still decreased 24 h post-administration, but no arrhythmias or visual changes were observed in the ECG complex. Body temperature and heart rate increased at the high dose of buprenorphine, even at 20-24 h after administration. Moreover, the high dose of buprenorphine induced a biphasic response in diastolic blood pressure, with an early and pronounced increase that, at 14 h after administration, reversed to a decrease, failing to normalize within 24 h post-dosage. The results indicate that buprenorphine induces long-lasting effects (such as body temperature and cardiovascular effects) in the rat after a single subcutaneous dose at 0.15 mg/kg bw.

Cardiovascular effects of xylazine recorded with telemetry in the dog.

Cardiovascular effects of xylazine have not been studied with telemetry in dogs. In the present study, the effects on cardiovascular parameters after intramuscular (i.m.) administration of 2.0 mg/kg xylazine were studied via telemetry in unrestrained dogs. Telemetry transmitters were implanted subcutaneously (s.c.) with a pressure catheter in the femoral artery. Cardiovascular effects and body temperature effects were assessed after i.m. administration of xylazine. Heart rate decreased for about 10 min and was continuously depressed during 60 min. Thereafter, heart rate slowly increased but had not fully reached pre-dose values 4 h after treatment. Both systolic and diastolic blood pressure increased immediately after administration of xylazine. The systolic blood pressure showed a peak increase for about 5-10 min and then decreased below the baseline value not normalizing within 90 min. The diastolic blood pressure peaked 5-10 min after xylazine administration but did not return to baseline level until 50 min after administration. Body temperature decreased continuously for about 90 min and remained low for more than 4 h after treatment. An additional administration of xylazine to the same individuals after a recovery period of 4 weeks induced exactly the same response in systolic and diastolic blood pressure and in heart rate. By using the telemetric recording system it was possible to continuously evaluate xylazine-induced cardiovascular responses in a way that is not possible with conventional techniques.

Effects of EDTA on trace elements and cardiovascular function in the anesthetised rabbit.

The present study was undertaken in order to study the effects of the broad-acting chelating agent CaNa2-EDTA on plasma trace elements and cardiovascular function in anesthetised New Zealand White rabbits. Trace elements are important for cardiovascular and immune functions and the rabbit is a well-accepted species in cardiovascular studies. The test compound CaNa2-EDTA was administered intravenously to rabbits at single doses of 4, 20, and 100 mg/kg. In addition, at 20 mg/kg, the effects of a second dose after 3 h were also investigated. Heart rate, blood pressure and body temperature were continuously monitored during a 6-h interval after injection of CaNa2-EDTA. Immediately before administration (-1 min) and at 3 and 6 h over the period of the experiment, the plasma cytokine response (tumor necrosis factor-alpha) and trace elements (Mn, Cu, Zn, Se, Ag, Cd, Hg, Pb) were measured. Regardless of dose, blood pressure was found to decrease, but no corresponding changes in heart rate were observed. Both a repeated administration of 20 mg/kg and a single dose of 100 mg/kg were detrimental and caused severe cardiovascular effects and lethality. alpha-TNF tended to increase, though only at 100 mg/kg. The electrocardiogram and body temperature were not affected by the treatment. The most pronounced trace element change was a dose-dependent increase in Mn that was equally pronounced at all time-points after the dose. There was an initial decrease in Cd at low dose levels (4 and 20 mg/kg) that turned into an increase after 6 h at 20 mg/kg and from 2 h at 100 mg/kg. A similar pattern with pronounced decreases at low dose levels was observed for Zn. Cu decreased similarly at all dose levels. For the other trace elements, no or inconsistent effects were observed. This model allows the study of concomitant cardiovascular and trace element changes during treatment with drugs and chelating agents preceding a possible lethal end point and associated pathophysiologic changes.

Effects of the antiviral WIN 54954 and the immune modulator LS 2616 on cachectin/TNF and gamma-interferon responses during viral heart disease.

The effects of the anti picornaviral drug WIN 54954 (5-(5-(2.6-dichloro-4-(4.5-dihydro-2-oxazolyl)phenoxy)pentyl)-3-me thyl- isoxazole) and the immune modulator LS 2616 (Quinoline-3-carboxamide) on plasma cachectin/TNFa and g-interferon (IFN-g) responses were investigated during the clinical course of a myocarditic coxsackievirus B3 (CB3) infection in the mouse. Virus as well as inflammatory and necrotic lesions were found in the hearts on days 4 and 7 post inoculation (p.i.), respectively. This was demonstrated using in situ virus RNA hybridization and immune histological techniques with monoclonal antibodies against lymphocyte subsets. The CB3 infection increased TNFa levels during the first three days of disease. This response was suppressed by WIN 54954 and LS 2616. IFN-g was decreased in infected mice in the late phase of the disease (day 11). Therapy, however, was protective, and WIN 54954 even tended to increase the IFN-g response at day 5, corresponding to the time when viremia peaks. These results indicate that cytokines may serve as prognostic markers in the therapy of infectious diseases and also that WIN 54954 and LS 2616 are both possible candidates for treatment of coxsackievirus infections in man. It is suggested that a combined antiviral and immune stimulatory treatment could be of future value.

Amelioration of intrathymic T cell development and peripheral T cell reactivities in autoimmune mice undergoing therapy with a novel immunomodulator.

MRL lpr/lpr mice develop a generalized autoimmune disease associated with a massive accumulation in the peripheral lymphoid organs of abnormal, phenotypically immature T cells. Both the lymphoadenopathy and the autoimmunity are thymus-dependent and likely to arise from an aberrant pathway of intrathymic differentiation. We here present the marked beneficial effects acquired in MRL lpr/lpr mice after in vivo administration of a novel immunomodulator called linomide. The highly altered pattern of thymic subpopulations in MRL lpr/lpr mice is normalized after linomide-treatment. Concomitantly, the peripheral T cell compartment, which in MRL lpr/lpr is highly deficient in producing and responding to IL-2, gains substantial functional reactivities. We propose that linomide acts by correcting the abnormal T cell development in autoimmune MRL lpr/lpr mice. This new immunomodulator may be a useful tool for providing insight into both the pathogenesis of autoimmune disorders and intrathymic differentiation.

Mechanism of action of the new immunomodulator LS2616 on T cell responses.

Spleen cells from mice treated with LS2616 display a highly increased response to the polyclonal T cell lectin ConA. The total number of splenic T cells, and the relative ratios between L3T4+ and Lyt-2+ T cells were not altered by LS2616 treatment. By dissecting the overall ConA response it was found that the number of ConA-inducible, IL-2 reactive T cells was unaffected, while ConA-induced IL-2 production was enhanced after LS2616 treatment. Spleen cells from LS2616 treated mice, depleted of G10 adherent macrophages (M phi) and reconstituted with M phi from untreated mice displayed normal levels of ConA responses. M phi depleted spleen cells from untreated animals, cocultured with M phi enriched populations from LS2616 treated animals resulted in an increased ConA response. Furthermore, spleen cells from treated mice were found to be excellent stimulators for alloantigen-induced T cell responses; when used as responders in MLC, however, these cells were comparable to responders from non-treated animals. Taken together the results demonstrate that LS2616 exerts an immunostimulatory effect on M phi, which indirectly facilitates polyclonal and antigen-specific T cell responses. The possible implications of this observation on various immunoregulatory events are discussed.

Effects of LS-2616 administration upon the autoimmune disease of (NZB x NZW) F1 hybrid mice.

Autoimmune (NZB X NZW) F1 female hybrid mice were treated with LS-2616, a recently developed substance with immunomodulating properties. Treatment was initiated at the age of 4 months (i.e. at the early stage of the disease) as well as at 7 months of age (i.e. after the development of established lupus-like disease). Control groups treated with cyclophosphamide and physiological saline were also studied. Beneficial therapeutic effects were obtained regardless of when the treatment was initiated and the dose of LS-2616 administered (1 and 8 mg/mouse/week). The effects of LS-2616 on longevity, splenomegaly and glomerulonephritis were pronounced and sometimes comparable to those of cyclophosphamide (1.8 mg/mouse/week). The results obtained suggest that LS-2616 may be useful in the treatment of autoimmune disease in man.

Successful treatment of autoimmunity in MRL/1 mice with LS-2616, a new immunomodulator.

Autoimmune MRL/1 mice were treated with a recently developed substance with immunomodulating properties, LS-2616. Treatment was initiated at the age of 8 weeks, before the onset of clinically apparent disease, and at 16 weeks of age, after development of established lupus disease. Beneficial therapeutic effects were obtained, even when LS-2616 was administered at the lowest dose tested (1 mg/mouse/week) to 16-week-old mice. The effects of LS-2616 on longevity, as well as on development of lymphadenopathy, splenomegaly, glomerulonephritis, and vasculitis, were pronounced and were comparable with those of cyclophosphamide. The results obtained suggest a potential role for LS-2616 in the treatment of autoimmune disease in humans.

Effects of the novel immunomodulator LS 2616 on the delayed-type hypersensitivity reaction to Bordetella pertussis in the rat.

Treatment of Sprague-Dawley rats with the compound LS 2616, a quinoline-3-carboxamide, enhanced the delayed-type hypersensitivity response (DTH) to recall antigens as judged by the specific accumulation of inflammatory cells after challenge with Bordetella pertussis in the pleural space. LS 2616 was effective when given both before sensitization and at the time of secondary antigen challenge. The effect of LS 2616 on DTH was dose-dependent. LS 2616 was highly effective in enhancing DTH in rats with suppressed cell-mediated immunity after treatment with anti-thymocyte globulin or prednisolone, indicating its possible value in the immunosuppressed state.

Lack of antiinflammatory activity of metronidazole.

Metronidazole was given to rats with experimentally induced inflammation to evaluate whether the drug has any antiinflammatory effect. Inflammation was caused by injection of Freund's complete adjuvant into a paw. The oedema of the paw measured on the 4th day was not influenced after metronidazole 20 mg/kg/day or 160 mg/kg/day, whereas phenylbutazone 80 mg/kg/day significantly decreased the volume of the paw. The concentration of orosomucoid did not differ in the group of rats given metronidazole 20 mg/kg/day as compared to the control group. However, the orosomucoid concentration was lower in the group given metronidazole 160 mg/kg/day, as was the case in the phenylbutazone group. In groups of rats with polyarthritis studied on the 14th and 21st day there was no difference of arthritic index, volume of paw or orosomucoid concentration in neither low nor high dose metronidazole as compared to the control groups. The phenylbutazone groups, however, showed a lower arthritic index, lower volume of paw and lower orosomucoid concentration.

In vitro metabolism of nicotine in liver of ageing mice.

14-C-nicotine was incubated with 10000 X g supernatant fraction of liver homogenate from female mice (C3H/TIF/BOM) 2, 12 and 18 months old. The rate of metabolism was measured by the determination of the oxidative nicotine metabolite continine and by determining the disappearance of nicotine. No significant changes between different ages were found either in the continine formation or the rate of disappearance of nicotine.