Combination of losartan with pirfenidone: a protective anti-fibrotic against pulmonary fibrosis induced by bleomycin in rats

Pirfenidone (PFD), one acceptable medication for treating idiopathic pulmonary fibrosis (IPF), is not well tolerated by patients at full doses. Hence, employing of some approaches such as combination therapy may be applicable for increasing therapeutic efficacy of PFD. Losartan (LOS), an angiotensin II receptor antagonist, could be a suitable candidate for combination therapy because of its stabilizing effect on the pulmonary function of IPF patients. Therefore, this study aimed to investigate the effects of LOS in combination with PFD on bleomycin (BLM)-induced lung fibrosis in rats. BLM-exposed rats were treated with LOS alone or in combination with PFD. The edema, pathological changes, level of transforming growth factor-β (TGF-β1), collagen content, and oxidative stress parameters were assessed in the lung tissues. Following BLM exposure, the inflammatory response, collagen levels, and antioxidant markers in rat lung tissues were significantly improved by PFD, and these effects were improved by combination with LOS. The findings of this in vivo study suggest that the combined administration of PFD and LOS may provide more potent protection against IPF than single therapy through boosting its anti-inflammatory, anti-fibrotic, and anti-oxidant effects. These results hold promise in developing a more effective therapeutic strategy for treating of lung fibrosis.

Preventive and therapeutic effects of azithromycin on acrylamide-induced neurotoxicity in rats

BACKGROUND

Acrylamide (ACR) can induce neurotoxicity through different pathways, including oxidative stress and apoptosis. Azithromycin is well-known for its antioxidant and anti-apoptotic properties.

OBJECTIVE

To evaluate the potential neuroprotective effect of azithromycin in an in vivo model of ACR-induced neurotoxicity, by investigating its impact on oxidative stress and apoptosis pathways.

METHODS

Male rats were divided into eleven groups at random (n = 6). 1:control (vehicle), 2:ACR (50 mg/kg, 11 days, I.P.), 3-7:ACR+ azithromycin (3.1, 6.25, 12.5, 25, 50 mg/kg, 11 days, I.P.), 8-9:ACR+ azithromycin (3.1, 6.25 mg/kg, from day 3-11), 10: ACR+ vitamin E (200 mg/kg, every other day, I.P.), 11. Azithromycin (50 mg/kg). Following the treatment period, a gait score examination was performed, and malondialdehyde (MDA), glutathione (GSH), Bcl-2-associated X protein (Bax)/B-cell lymphoma 2 (Bcl-2) ratio and caspase-3 levels in the cerebral cortex were measured.

RESULTS

Gait abnormality, a drop in GSH, and an increase in lipid peroxidation, Bax/Bcl-2 ratio, and caspase-3 levels were all significantly triggered by ACR in the cerebral cortex versus the control group. Azithromycin 3.1 and 6.25 mg/kg with ACR and azithromycin 6.25 mg/kg with ACR from day 3-11 ameliorated movement disorders caused by ACR. Azithromycin in all doses and both protocols along with ACR decreased the MDA level. Azithromycin (3.1, 6.25 mg/kg) along with ACR in both protocols increased the level of GSH, reduced the Bax/Bcl-2 ratio and caspase-3 amounts in the brain tissue versus the ACR group.

CONCLUSIONS

Administration of azithromycin had both preventive and therapeutic effects on ACR-induced neurotoxicity through its antioxidant and antiapoptotic properties.

Losartan enhances the suppressive effect of pirfenidone on the bleomycin-induced epithelial-mesenchymal transition and oxidative stress in A549 cell line

Objectives

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease. Despite the promising anti-fibrotic effect, the toleration of pirfenidone (PFD) by the patients in full dose is low. Combination therapy is a method for enhancing the therapeutic efficiency of PFD and decreasing its dose. Therefore, the present study evaluated the effect of a combination of losartan (LOS) and PFD on oxidative stress parameters and the epithelial-mesenchymal transition (EMT) process induced by bleomycin (BLM) in human lung adenocarcinoma A549 cells.

Materials and Methods

The non-toxic concentrations of BLM, LOS, and PFD were assessed by the MTT assay. Malondialdehyde (MDA) and anti-oxidant enzyme activity including catalase (CAT) and superoxide dismutase (SOD) were assessed after co-treatment. Migration and western blot assays were used to evaluate EMT in BLM-exposed A549 after single or combined treatments.

Results

The combination treatment exhibited a remarkable decrease in cellular migration compared with both single and BLM-exposed groups. Furthermore, the combination treatment significantly improved cellular anti-oxidant markers compared with the BLM-treated group. Moreover, combined therapy markedly increased epithelial markers while decreasing mesenchymal markers.

Conclusion

This in vitro study revealed that the combination of PFD with LOS might be more protective in pulmonary fibrosis (PF) than single therapy because of its greater efficacy in regulating the EMT process and oxidative stress. The current results might offer a promising therapeutic strategy for the future clinical therapy of lung fibrosis.

Alpha-mangostin Protects PC12 Cells Against Neurotoxicity Induced by Cadmium and Arsenic

Arsenic and cadmium are nonessential elements that are of importance in public health due to their high toxicity. Contact with these toxic elements, even in very small amounts, can induce various side effects, including neurotoxicity. Oxidative stress and apoptosis are part of the main mechanisms of arsenic- and cadmium-induced toxicity. Alpha-mangostin is the main xanthone derived from mangosteen, Garcinia mangostana, with anti-oxidative properties.In this study, PC12 cells were selected as a nerve cell model, and the protective effects of alpha-mangostin against neurotoxicity induced by arsenic and cadmium were investigated. PC12 cells were exposed to cadmium (5-80 µM) and arsenic (2.5-180 µM) for 24 h. Cytotoxicity, reactive oxygen species (ROS) production, and the protein expression of Bax, Bcl2, and cleaved caspase 3 were determined using MTT assay, fluorimetry, and western blot, respectively.Arsenic (10-180 µM) and cadmium (50-80 µM) significantly reduced cell viability. IC₅₀ values were 10.3 ± 1.09 and 45 ± 4.63 µM, respectively. Significant increases in ROS, Bax/Bcl-2 ratio, and cleaved caspase-3 were observed after arsenic and cadmium exposures. Cell viability increased and ROS production decreased when cells were pretreated with alpha-mangostin for 2 h. Alpha-mangostin reduced the increased level of cleaved caspase-3 induced by cadmium and decreased the elevated level of the Bax/Bcl-2 ratio after arsenic exposure.Alpha-mangostin significantly increased cell viability and reduced oxidative stress caused by cadmium and arsenic in PC12 cells. Moreover, alpha-mangostin reduced cadmium-induced apoptosis through the reduction in the level of cleaved caspase 3. Further studies are required to determine the different mechanisms of alpha-mangostin against neurotoxicity induced by these elements.

The effect of early handling on anxiety-like behaviors of rats exposed to valproic acid pre-and post-natally

INTRODUCTION

Autism spectrum disorder (ASD) is a complex, behaviorally defined disorder of the immature brain as a result of genetic and environmental risk factors, such as prenatal exposure to valproic acid (VPA). This syndrome is known for its high prevalence. On the other hand, postnatal manipulations have been shown to affect brain development, cortical neuroscience, and pituitary-adrenal activity. In early handling (EH) procedure, pups are removed from their mother on a daily basis from birth to lactation, are physically touched, and exposed to the (a) new environment. In the present study, the effect of EH on anxiety-like behaviors in rats exposed pre- and post-natally to valproic acid was investigated.

METHODS

Pregnant Wistar rats were randomly separated into six groups which are prenatal saline, Prenatal VPA, Prenatal VPA + EH and postnatal saline, Postnatal VPA, Postnatal VPA + EH. VPA administration was performed either on ED12.5 (600 mg/kg, i.p.) or PD 2-4 (400 mg/kg, s.c.). In the groups receiving EH, pups underwent physical handling from PD 1 to 21. On postnatal day 21 all offspring were weaned and the behavioral tests were performed on 30 and 31 days of age. Elevated plus maze and open field tests were used to investigate anxiety-like behaviors.

RESULTS

The results revealed that intraperitoneal injection of valrpoic acid (600 mg.kg) during pregnancy significantly reduced OAT% in males (p < 0.01) and females in a non-significant manner (p > 0.05). In comparison, rearing counts of prenatal VPA groups significantly increased in female sex (p < 0.05) in the EPM test. Following postnatal VPA administration (400 mg/kg), decrease in the time spent in central zone occurred in female rats in the open filed (p < 0.05), as well as a significant increase in the number of grooming of the male sex (p < 0.05). Applying Early Handling to male and female Wistar rats receiving prenatal VPA significantly reversed the OAT% fall (p < 0.05). EH in postnatally VPA exposed animals significantly decreased the OAT% and OAE% criteria, while increasing the locomotor activity of the female sex (p < 0.05). Compared with the postnatal VPA group, no significant change was reported in the EPM performance of postnatal VPA + EH group in neither of sexes (p > 0.05).

CONCLUSION

The findings of this study suggest that injections of valproic acid during pregnancy lead to anxiety-like behaviors in male offspring, which EH can improve (attenuate) to some extent. VPA injections on the second to the fourth day of infancy did not have a profound effect on anxiety level. Further behavioral studies need to be performed using other devices to investigate anxiety-like behaviors and to determine the mechanisms involved in these behaviors.

Resveratrol Attenuates Learning, Memory, and Social Interaction Impairments in Rats Exposed to Arsenic

Arsenic (As) toxicity has deleterious effects on human health causing disorder in the brain. The aim of this study was to investigate the possible neuroprotective effect of resveratrol (RSV) on arsenic-induced neurotoxicity in rats. Neurotoxicity in rats was developed by treating As 10 mg/kg/day for 21 days orally. Animals were put into seven groups: control, vehicle, As, As+RSV10, As+RSV20 mg/kg, RSV10, and RSV20 mg/kg. Behavioral assessments such as the social interaction test, novel object recognition test, elevated plus maze, open field, the Morris water maze, in addition to assessment of biomarkers such as ferric reducing ability of plasma assay, glutathione assay, and malondialdehyde assay, were used to evaluate the effects of RSV on cognitive impairment and molecular changes induced by As. The results showed that cognitive performance impaired in As rats. RSV20 mg/kg significantly could ameliorate behavioral changes like spatial learning in days 3 and 4 (p < 0.05), recognition learning and memory (p < 0.01), disabilities in motor coordination and stress (p < 0.05), increased anxiety (p < 0.05), and social interaction deficit (sociability (p < 0.001) and social memory (p < 0.05)). RSV20 mg/kg also attenuated molecular modifications like decreased antioxidant power (p < 0.001), reduced glutathione content (p < 0.05), and increased malondialdehyde level (p < 0.05) induced by As. In addition to oxidative stress assessments, RSV10 mg/kg could significantly increase FRAP (p < 0.01) and GSH (p < 0.05); however, MDA was not significantly increased. Our current behavioral findings suggest that RSV has neuroprotective effects against AS toxicity.

Serum levels of Organochlorine Pesticides and Breast Cancer Risk in Iranian Women

Breast cancer is a multifactorial disease and its etiology is linked to multiple risk factors. There are shreds of controversial evidence that exposure to organochlorine pesticides (OCPs) are important in the etiology of breast cancer. The present study aimed to determine the circulating levels of OCPs in patients with breast tumors in Southeastern of Iran. This case-control study included 27 patients with malignant breast tumors (MBT), 31 patients with benign breast tumors (BBT), and 27 healthy women as a control group. Serum OCPs levels, including α-hexachlorocyclohexane (α-HCH), β-HCH, γ-HCH, 2,4-dichlorodiphenyltrichloroethane (2,4-DDT), 4,4-DDT, 2,4-dichlorodiphenyldichloroethylene (2,4-DDE), and 4,4-DDE, were measured using gas chromatography. Our data revealed significantly higher concentrations of 2,4-DDT in MBT and BBT groups compared with control ones (P < 0.001 for both comparisons). Patients with breast cancer suffered significantly higher accumulation levels of 4,4-DDE compared with control subjects (P = 0.04). Significant correlations were found among organochlorine compounds with each other in both patients' groups. There was a significant positive correlation between body mass index and serum levels of 2,4-DDT in BBT group (r = 0.407, P = 0.02). The present findings suggest that the serum levels of 4,4-DDE and 2,4-DDT are associated with an increase in the risk of breast cancer in Southeastern women of Iran.

Effect of Crocus sativus extracts and its active constituent safranal on the harmaline-induced tremor in mice

OBJECTIVES

Due to unsatisfactory response or intolerable side effects of current drugs, treatment of essential tremor remains inadequate. Thus, we aimed to investigate the protective and therapeutic effects of aqueous and ethanolic extracts of Crocus sativus (saffron), and its active consistent, safranal, on the harmaline-induced tremor in mice.

MATERIALS AND METHODS

To induce tremor, harmaline (30 mg/kg) was injected intraperitoneally. Test groups were also given the aqueous and ethanolic extracts of saffron (40, 80, and 160 mg/kg) as well as safranal (0.1, 0.3, and 0.5 ml/kg), intraperitoneally, 10 min before harmaline administration (prophylactic study) or 10 min after the onset of tremors (curative study). The latency of onset, duration, and intensity of tremor were recorded.

RESULTS

The extracts (80 and160 mg/kg) dose dependently attenuated duration of harmaline-induced tremors as did reference drug, propranolol (2 and 5 mg/kg). Only the highest dose of extracts (160 mg/kg) attenuated intensity of harmaline-induced tremors throughout the study. Safranal at the doses of (0.1 and 0.3 ml/kg) but not 0.5 ml/kg attenuated duration and intensity of tremor. Onset of tremor increased with the extracts (80 and 160 mg/kg) in prophylactic study, as the effect observed with propranolol at the dose of 5 mg/kg. Safranal did not affect the latency of tremor.

CONCLUSION

Both aqueous and ethanolic extracts of saffron and with a less effect, low doses of safranal, have relatively protective and suppressive effects on the harmaline-induced tremor and different constituents of extracts seem to participate in the protective effects against harmaline induced tremor.

Comparison of gastric ulcerogenicity of percolated extract of Anacardium occidentale (cashew nut) with indomethacin in rats

In traditional Iranian medicine, the core of the fruit of Anacardium occidentale (cashew nut) has been used in the management of the pain. In this study gastric ulcerogenicity effect of the percolated extract of A. occidentale was investigated in rats. The extract or indomethacin (200, 300, 400 and 800 mg/kg) was administrated orally. In the control group normal saline (5 ml/kg) was used. After getting extract, indomethacin or normal saline, animals were slaughtered. The stomachs were detached and 10ml of 2% formalin injected in to the stomach for fixing the internal coat of the gastric wall. The stomachs were then slitted open near the bigger curvature and lacerations in the glandular part were evaluated. The ulcer index was determined using j-score. Data demonstrated that the oral dose of 200mg/kg of the extract did not provoke any ulcerogenic consequence in the rat's stomach. Gastric ulcerginicity of the extract at the doses of 300, 400 and 800 mg/kg was less than the similar doses of indomethacin (p<0.01). Therefore, A. occidentale is an appropriate plant for ongoing search for establishing an analgesic agent with low gastro-intestinal side effects for clinical use.

Investigation of Hypericum perforatum extract on convulsion induced by picrotoxin in mice

Therapeutic effect of Hypericum perforatum L. has been well known. The aim of this study is to investigate the anticonvulsant effects of Hypericum methanolic extract against seizure induced by picrotoxin in mice. The study were performed on four groups of animals. They received percolated extract of Hypericum perforatum at the doses of 25, 50, 100 & 200 mg/kg intra peritoneally. After 20 minutes animals received picrotoxin 10 mg/kg for induction of seizure. Latency of seizure, duration of seizure, death latency and percent of mortality were determined. The results indicated that latency of seizure increased in pretreated group with the dose of 50 mg/kg (p<0.01). The higher dose of extract 200 mg/kg significantly decrease duration of seizure and death latency. It maybe due to unknown ingredients in this plant or producing concentrations higher than the therapeutic level. The results showed that Hypericum perforatum L. at the dose of 50 mg/kg maybe have some beneficial effect in seizure induced by picrotoxin and this plant is suitable for continuing search in this field.

Study of the anti-inflammatory and analgesic effects of novel rigid benzofuran-3, 4-dihydroxy chalcone by formalin, hot-plate and carrageenan tests in mice

It is reported that dihydroxy chalcones have analgesic and anti-inflammatory effects. Study of the structure activity relationship (SAR) shows that benzofuran-3-one derivatives may be more effective in this respect. In this study, a new (Z)-2-(3,4-dihydroxybenzylidene)-5-methoxybenzofuran-3(2H)-one (compound 5) was synthesized and its analgesic and anti-inflammatory effects were evaluated by formalin, carrageenan and hot-Plate methods in mice. The results showed that, compound 5 induced significant antinociceptive and anti-inflammatory effect (P<0.01). Maximum analgesia (42.6%) was obtained at dose of 25 mg/kg in the first phase of formalin test. The effect of compound 5 was higher (87.7%) in chronic phase of inflammation induced by formalin (P<0.01). Administration of 25 mg/kg of compound 5 inhibited the inflammation induced by carrageenan, 32.8% and 41.7%, 1 and 3 hour after carrageenan injection, respectively. In addition, this dose of compound 5, induces significant analgesia (20.2%) in hot plate test 45 minutes after injection (P<0.01). Therefore it seems that compound 5 has potential for discovery of a compound with potent anti-inflammatory and analgesic effects and its scaffold could be use for further structural modifications.

Evaluation of anti-inflammatory and analgesic activity of a novel rigid 3, 4-dihydroxy chalcone in mice

There have been many reports indicating the analgesic and anti-inflammatory effects of 3,4-dihydroxychalcones. We have designed and synthesized a rigid 3,4-dihydroxychalcone (RDHC) as a possible drug effecting inflammation and nociception. The analgesic and anti-inflammatory effects were evaluated by formalin and hot-plate tests, respectively. The results showed that RDHC induced significant antinociceptive and anti-inflammatory effects (P < 0.01). Maximum analgesia (63.7%) was observed at 37.5 mg/kg in the first phase of the formalin test. The effect of RDHC was higher in the chronic phase (inflammation phase) of the formalin test (86.4%, P < 0.01). In addition, a significant analgesia (maximum possible effect; MPE = 30.1%) was observed in the hot plate test 45 min after injection of 37.5 mg/kg RDHC (P < 0.01). As a result of our findings, this new RDHC could be suggested for further pharmacological studies.

Synthesis and antioxidant properties of substituted 3-benzylidene-7-alkoxychroman-4-ones

A series of 3-benzylidene-7-alkoxychroman-4-one derivatives were synthesized and evaluated for their antioxidant activities. The antioxidant activity was assessed using three methods, namely, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and thiobarbituric acid reactive substances (TBARS) assays. 3-Benzylidene-7-alkoxychroman-4-one derivatives bearing catecholic group on benzylidene moiety exhibited excellent antioxidant activity. Compounds having catechol moiety exhibited potent antioxidant activities in all tested methods and they were more active than the reference drug, Trolox.

In vitro cytotoxicity and phototoxicity of N-piperazinyl quinolone derivatives with a 2-thienyl group

We examined the cytotoxic potential of nine N-[2-substituted-2-(2-thienyl)ethyl] piperazinyl quinolone derivatives on human oral epithelial mouth carcinoma (KB) and human squamous carcinoma (A431) cell lines. Phototoxic properties of these compounds were also evaluated by mouse 3T3 fibroblast under ultraviolet-A (UVA) irradiation. The percent of cell viability was evaluated by MTT assay. Compound 6 having a 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] group attached to N4 position of piperazine ring of enoxacin showed the highest cytotoxicity potential on both A431 and KB cell lines (IC50 of 3.11+/-0.52 and 4.91+/-1.94 microg/ml, respectively). While some of the other tested compounds exhibited clear phototoxic potential in 3T3 cell line, compound 6 showed only a minor potential of phototoxicity. These findings suggest the high potential of 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] derivative of enoxacin as a cytotoxic compound with low potency of phototoxic reactions. The mentioned chemical was identified to be of special interest for further characterization.

The Analgesic Effect of Tribulus terrestris Extract and Comparison of Gastric Ulcerogenicity of the Extract with Indomethacine in Animal Experiments

Tribulus terrestris has been used in traditional medicine for relieving rheumatic pain and as an analgesic plant for a long time. In this investigation the analgesic effect of methanolic extract of this plant on male albino mice was evaluated by formalin and tail flick test. Extraction of the fruits of the plant was done by two different methods (suxheletion and percolation) with methanol 80%. The percolated extract was injected intraperitoneally in mice at 50, 100, 200, 400, and 800 mg/kg. The results showed that a dose of 100 mg/kg of percolated extract had the highest significant analgesic effect compared to the control group (P < 0.01) in formalin and tail flick test. There is no significant difference in the analgesic effect of suxheleted and percolated extract. The analgesic effect of the extract was lower than morphine, 2.5 mg/kg in both tests, and higher than ASA 300 mg/kg in chronic phase of pain in formalin test (P < 0.05). Pretreatment of animal with naloxone did not change the analgesia induced by the plant extract in both tests, therefore the involvement of opioid receptor in the analgesic effect of this plant was excluded. The results of ulcerogenic studies indicate that the gastric ulcerogenecity of plant extract is lower than the indomethacin in the rat's stomach. It can therefore be concluded that T. terrestris extract has a suitable analgesic effect and further studies are required to produce a more effective product of this plant to substitute for conventional analgesic drugs.

Evaluation of the analgesic effect of Echium amoenum Fisch & C.A. Mey. extract in mice: possible mechanism involved

Echium amoenum Fisch & C.A. Mey. has been used in Iranian traditional medicine as demulcent and analgesic in common cold from long ago. In this investigation, the analgesic effect of the methanolic extract of the petals of this plant on male albino mice was evaluated by formalin and hot-plate test. The methanolic percolated extract with different doses 5, 10, 20 and 30 mg/kg were injected intraperitoneally to mice. The results showed that the dose of 10 mg/kg of extract had the highest analgesia in formalin (P<0.05) and hot-plate test (P<0.01) compared to the control group. The analgesic effect of extract was lower than morphine 2.5 mg/kg and ASA 300 mg/kg in the chronic phase of pain in formalin test (P<0.05) and in hot-plate test too (P<0.05). Pretreatment of animal with naloxone 4 mg/kg, s.c. 5 min before extract, decreased the analgesia induced by extract in hot-plate and acute phase of formalin tests; therefore, the opioid receptor may be involved at least partly in the analgesic effect of Echium amoenum extract. The results suggested that Echium amoenum extract has a suitable analgesic effect and further studies are required to evaluate these effects and the potential of the plant.

Effect of adenosine receptor agonists and antagonists on morphine-induced catalepsy in mice

Effects of adenosine receptor agonists and antagonists on morphine-induced catalepsy in mice were investigated. The adenosine agonists, NECA (5'-N-ethylcarboxamidoadenosine) and S-PIA (S(+)-N6-(2-phenylisopropyl)adenosine) in doses which did not induce any response, increased the cataleptogenic effect produced by morphine. However, the morphine response was decreased and increased by the lower and higher doses of the adenosine receptor agonist, CHA (N6-cyclohexyladenosine), respectively. The adenosine receptor antagonist, theophylline, decreased, but 8-phenyltheophylline increased, the response induced by morphine. Naloxone inhibited the catalepsy induced by morphine or morphine + NECA but not that induced by NECA alone. It is concluded that adenosine A2 receptor activation increases, while adenosine A1 receptor stimulation decreases, the morphine cataleptogenic response. The response to morphine may be mediated through opioid and adenosine receptor mechanisms.

Effect of picrotoxin on antinociception in the formalin test

Subcutaneous injection of diluted formalin (0.25 microliter of 0.5%) caused a biphasic pain response in mice. The first phase of pain was observed during the first 5 min., while the second phase occurred 10-30 min. after formalin administration. With the formalin test, it was found that the antinociception produced by the GABA-A antagonist, picrotoxin, and the GABA-B antagonist, phaclofen, was abolished when employed in combination. The opioid antagonist naloxone and antimuscarinic atropine also decreased the picrotoxin response. However, sulpiride, SCH 23390, phenoxybenzamine and propranolol did not alter the picrotoxin response. Administration of naloxone, sulpiride and propranolol showed a pain response. The data indicate that dopaminergic and adrenergic mechanisms may not be involved in the picrotoxin antinociceptive effect. However, postsynaptic GABA-A and GABA-B may be involved in the drug effect, and involvement of opioid or cholinergic systems can not be excluded.

On the mechanisms by which theophylline changes core body temperature in mice

In the present work, the effects of neurotransmitter antagonists on theophylline-induced changes in body temperature were investigated. Intraperitoneal (i.p.) administration of a low dose of theophylline (25 mg/kg) induced slight hyperthermia, while high doses (75 and 100 mg/kg) induced hypothermia. The hypothermic effect of theophylline was decreased by pretreatment of animals with the dopamine D2 receptor antagonists sulpiride (15 and 30 mg/kg i.p.) and pimozide (0.125 and 0.25 mg/kg i.p.), the muscarinic receptor antagonist atropine (2.5 and 5 mg/kg i.p.) and the 5-HT receptor antagonist metergoline (0.25 mg/kg i.p.). However, the dopamine D1 receptor antagonist SCH 23390 (0.05 and 0.5 mg/kg i.p.), the alpha-adrenoceptor antagonist phenoxybenzamine (2.5 and 5 mg/kg i.p.) and the beta-adrenoceptor antagonist propranolol (5 and 10 mg/kg i.p.) did not after the theophylline response. In reserpinized mice, theophylline caused a dose-dependent rise in body temperature. The response was blocked in animals pretreated with phenoxybenzamine, propranolol and atropine. Single treatment of animals with either SCH 23390 or sulpiride, and also with a combination of the two drugs, decreased the hyperthermia induced by theophylline in reserpinized mice. Pimozide or metergoline did not have any effect in this respect. These data suggest that the hypothermic response to theophylline may be mediated through dopaminergic, cholinergic and serotonergic mechanisms. The hyperthermic action of theophylline in reserpinized animals may be mediated through dopaminergic, cholinergic and adrenergic systems. Overall it seems likely that theophylline interacts with modulatory mechanisms involved in thermoregulation.

On the mechanism(s) of morphine-induced hypothermia

The effects of morphine on core body temperature of mice in the presence or absence of catecholamine receptor antagonists were examined. Administration of different doses of morphine (20, 30 and 40 mg/kg) to mice caused a hypothermic effect. Pre-treatment of animals with the opioid receptor antagonist naloxone (1, 1.5 and 3 mg/kg), the D-2 receptor antagonists sulpiride (25 and 50 mg/kg), pimozide (0.0625, 0.125 and 0.25 mg/kg) and the adenosine receptor antagonist theophylline (25 and 50 mg/kg) decreased the morphine-induced hypothermia. The D-1 receptor antagonist SCH 23390 (0.1 and 0.2 mg/kg), the peripheral D-2 antagonist domperidone (10 and 30 mg/kg), the serotonin (5-HT) antagonist methysergide (5 and 10 mg/kg), the adrenoceptor antagonist phenoxybenzamine (2.5 and 5 mg/kg) and the β-adrenoceptor antagonist propranolol (5 and 10 mg/kg) did not inhibit the morphine response. The antimuscarinic drug atropine (5 and 10 mg/kg) caused a slight decrease in the morphine response. In animals pre-treated with reserpine (5 mg/kg), a hyperthermic response was observed after morphine injection. It is concluded that indirect dopaminergic or adenosine receptor mechanism(s) may be involved in the morphine-induced hypothermia in mice.

Involvement of adenosine receptors in mouse thermoregulation

The effects of the activation of adenosine receptors on core body temperature of mice have been studied in the present investigation. Intraperitoneal (i.p.) injection of non-selective adenosine agonists 5'-N ethyl- carboxamide adenosine (NECA; 0.001, 0.01 and 0.05 mg/kg), R-(N(6)-phenylisopropyl)-adenosine (R-PIA; 0.01, 0.1 and 0.25 mg/kg) and selective A(1) adenosine agonist N(6)-cyclohexyladenosine (CHA; 0.1, 0.25 and 0.4 mg/kg) reduced core body temperature. However, R-PIA and CHA were less potent than NECA in reducing the core body temperature. Theophylline (12.5, 25 and 50 mg/kg) blocked the hypothermia of the adenosine agonists. Pre-treatment of animals with selective A(1) adenosine antagonist 8-phenyltheophylline (8-PT; 0.5, 1 and 2 mg/kg) decreased the hypothermic response of CHA but not of NECA and R-PIA. 8-PT potentiated the hypothermia induced by R-PIA. These results suggest that activation of both A(1) and A(2) adenosine receptors decreases core body temperature in mice.