IP Administration Research Articles

Antipanic-like effect of serotonin reuptake inhibitors in the elevated T-maze

There has been an increasing interest in the development of animal models that address different types of anxiety disorders. The elevated T-maze (ETM) was developed based on the assumption that inhibitory avoidance and one-way escape are respectively related to generalized anxiety (GAD) and panic disorder (PD). Although anxiolytic effects on the inhibitory avoidance task have been shown for drugs used in clinical settings to treat GAD, positive effects of antipanic drugs in one-way escape have been described only for imipramine. The study extends the pharmacological validation of the ETM to other serotonin reuptake inhibitors that have antipanic properties. To this end, we investigated the effects of acute and chronic (21 days) IP administration of clomipramine (3, 10 and 30 mg/kg) and fluoxetine (5, 10 and 15 mg/kg). Buspirone (0.3, 1 and 3 mg/kg) was used as a negative control since the drug is effective in GAD but not PD. Chronically, both clomipramine and fluoxetine impaired one-escape, an antipanic-like effect, not altering avoidance latencies. Clomipramine, but not fluoxetine, also affected locomotion. Acute injection of buspirone impaired avoidance, an anxiolytic-like effect. Neither acute nor chronic buspirone altered one-escape. These results corroborate the suggestion that one-way escape is related to PD.

Ultrasound-guided percutaneous delivery of adenoviral vectors encoding the beta-galactosidase and human factor IX genes to early gestation fetal sheep in utero.

In utero gene therapy may provide treatment of genetic diseases before significant organ damage, allow permanent genetic correction by reaching stem cell populations, and provide immune tolerance against the therapeutic transgenes and vectors. We have used percutaneous ultrasound-guided injection as a minimally invasive fetal procedure. First-generation adenoviruses encoding the nuclear localizing beta-galactosidase reporter gene or the human factor IX (hFIX) gene, or colloidal carbon were delivered via the umbilical vein (UV, n = 4), heart (intracardiac [IC], n = 2), liver parenchyma (intrahepatic [HE], n = 11), peritoneal cavity (intraperitoneal [IP], n = 14), skeletal musculature ([intramuscular [IM], n = 11), or the amniotic cavity (intraamniotic [IA], n = 14) to early-gestation fetal sheep (0.3 gestation = day 33-61). Postmortem analysis was performed at 2, 9, or 28 days after injection. Although fetal survival was between 77% and 91% for IP, HE, IA, and IM routes, no fetuses survived UV or IC procedures. The hFIX levels reaching 1900 and 401 ng/ml (IP), 30 ng/ml (HE), 66.5 and 39 ng/ml (IA), and 83 and 65.5 ng/ml (IM), respectively, were determined 2 days after injection and decreased at birth to 16.5 ng/ml (IP), 7 ng/ml (HE), 4.5 ng/ml (IA), and 4 and 0 ng/ml (IM). Polymerase chain reaction (PCR) and immunohistochemistry showed broadest hFIX transgene spread and highest localised beta-galactosidase expression, respectively, after IP administration. Antibodies were observed against vector but not against hFIX.

Brain Na+,K(+)-ATPase inhibition induced by arginine administration is prevented by vitamins E and C.

Hyperargininemia is a metabolic disorder caused by deficiency of arginase activity resulting in tissue accumulation of arginine and neurological dysfunction. We have previously demonstrated that arginine induces oxidative stress and decreases Na+,K(+)-ATPase in rat midbrain. In the present study we investigated the action of vitamins E and C on the inhibition of Na+,K(+)-ATPase provoked by arginine in the midbrain of 60-day-old rats. Animals were pretreated for 1 week with daily IP administration of saline (control) or vitamins E (40 mg/kg) and C (100 mg/kg). Twelve h after the last injection, animals received one injection of arginine (0.8 micromol/g of body weight) or saline. Chemiluminescence was significantly increased, whereas total antioxidant capacity and Na+,K(+)-ATPase activity were significantly decreased. Furthermore, treatment with vitamins E and C prevented these effects. If these effects also occur in the human condition, it is possible that antioxidant administration might slow the progression of neurodegeneration in this disorder.

Effect of pyrene on hepatic cytochrome P450 1A (CYP1A) expression in Nile Tilapia (Oreochromis niloticus).

The effect of pyrene on the regulation of the gene expression of cytochrome P4501A ( CYP1A) was studied in tilapia (Oreochromis niloticus), a tropical fish of great ecological and economical importance. To evaluate CYP1A mRNA, tilapia CYP1A cDNA was cloned, sequenced, and compared with those CYP1A reported sequences in the GeneBank DNA database. The top seven matches corresponded to CYP1A from other teleosts. Hepatic CYP1A mRNA levels showed a significant increase at day 1 after pyrene injection (20 mg kg(-1) body weight [BW]), and this CYP1A mRNA levels did not return to basal levels for up to 5 days. The immunoblot analysis of CYP1A protein levels using polyclonal rabbit-anti-trout antibodies in the liver of pyrene-treated (20 mg kg(-1) BW) tilapias showed a 1.9-fold increase at day 3 after injection. Ethoxyresorufin- O-deethylase (EROD) activity increased 18-fold with respect to control fish at day 3 after injection. CYP1A protein and EROD activity remained increased for 5 days after a single pyrene IP administration. Similarly, the highest concentration of 1-hydroxypyrene (1-OH pyrene) in bile was observed in fish sacrificed at day 3 after injection. EROD activity and 1-OH pyrene concentration showed a statistically significant correlation (r = 0.85) according to the Spearman test, suggesting the participation of this cytochrome in the biotransformation of pyrene.

Chronic Blockade of Neurotensin Receptors Strongly Reduces Sensitized, but Not Acute, Behavioral Response to D-amphetamine

This study investigated the effect of a chronic blockade of neurotensin (NT) receptors on the sensitized behavioral response to amphetamine using a nonpeptide NT receptor antagonist, SR 48692. Rats received four injections of D-amphetamine (0.5 or 1 mg/kg, IP) every other day (day 1, 3, 5 and 7) and were then challenged with the same dose of amphetamine after a 6-day withdrawal (day 14) to establish the presence of locomotor sensitization. Daily administration of SR 48692 (1 mg/kg, IP) throughout the amphetamine regimen (day 1 to day 14) almost completely blocked the sensitized locomotor response to amphetamine without affecting stereotyped behaviors (experiment 1). The decreased amphetamine-induced sensitization in chronically SR 48692-treated rats did not appear to result from an influence on basal locomotor activity, as chronic SR 48692 treatment did not modify the spontaneous locomotor activity developed in response to mild stresses (experiment 2). Moreover, we showed that chronic pretreatment with SR 48692 (1 mg/kg, 14 daily IP injections) had no effect on the locomotor activation induced by a single IP administration of amphetamine (experiment 3). These data suggest that a sustained blockade of NT receptors considerably reduces the sensitized behavioral response to amphetamine without altering the acute effect of this psychostimulant or the locomotor activation induced by a mild stress. This ability of SR 48692 to specifically reduce the behavioral sensitization to amphetamine suggests that NT receptor antagonists could have potential clinical utility in the treatment of some psychiatric disorders.

Evidence for calcium-sensing receptor mediated stanniocalcin secretion in fish

The secretion of parathyroid hormone (PTH) and calcitonin (CT) in mammals are both tightly regulated by the prevailing levels of extracellular ionic calcium (Ca 2+). And, it is now widely recognized that both of these Ca 2+ effects are mediated exclusively through a seven transmembrane calcium sensing receptor or CaR. As in the case of PTH and CT, the secretion of stanniocalcin (STC) in fish is tightly regulated by the levels of extracellular Ca 2+. Fish STC functions as an anti-hypercalcemic hormone such that a rise in extracellular Ca 2+ above the physiological set-point of ∼1.2 mM provokes an immediate secretory response. Whether or not Ca 2+-regulated STC secretion in fishes is mediated by similar type of receptor has never been addressed. Here, we have found that Ca 2+-stimulated STC secretion in salmon is mimicked by CaR mimetics, pharmacological agents that increase the sensitivity of the CaR to calcium. NPS 467, a small organic molecule that acts as a positive allosteric modulator of the CaR and alters calciotropic hormone secretion in mammals, was examined for effects on serum levels of STC in trout. The IP administration of NPS R-467 had time and dose-dependent stimulatory effects on STC secretion that were indistinguishable from those of Ca 2+ loading. The effects of NPS 467 were stereospecific and had no effects on serum CT. NPS 467 induced STC release was also manifested by a downstream physiological response; the inhibition of gill calcium transport. A cDNA clone was amplified from a fish corpuscle of Stannius cDNA library with high homology to the human CaR. RT-PCR revealed that this transcript was also present in gill, kidney, pancreas, brain, muscle and spleen. These findings suggest that Ca 2+-stimulated STC secretion in fishes is mediated by a calcium ion-sensing receptor similar to that in mammals.

8-Amino-5-nitro-6-phenoxyquinolines: Potential Non-peptidic Neuropeptide Y Receptor Ligands

The synthesis and pharmacological evaluation of analogues of PD 160170, a neuropeptide Y1 (NPY) receptor antagonist are reported. Phamacomodulation of this 8-amino-5-nitro-6-phenylsulfonylquinoline was carried out by replacing the sulfone moiety by oxygen. The corresponding ethers 11 - 16 were obtained by nucleophilic substitution of 8-acetamido-6-chloro-5-nitroquinoline 4 with phenols, followed by acidic hydrolysis of the intermediary amides 5 - 10. The test compounds 11 - 16 exerted no appreciable Y1 activity and they were also inactive in terms of Y5 receptor binding; their IC 50 values were >1 μM and 10 μM, respectively. The dramatic decrease in potency resulting from replacement of the sulfone function by an ether was confirmed by IP administration of 16 to ob / ob mice; after a 4-day administration, no decrease in food consumption or weight was observed.

Effect of administration route on FES uptake into MCF-7 tumors

We have observed that intraperitoneal administration of [ 18F]fluoroestradiol (FES), a radiolabeled estrogen receptor ligand, results in higher abdominal organ uptake and slower blood clearance than intravenous administration in female mice. In SCID mice bearing MCF-7 human tumors SC, IP administration resulted in tumor uptake that was only about one third that obtained with IV administration. Thus, the route of administration of a radiopharmaceutical for imaging or radiotherapy of a tumor in the abdomen, an ovarian tumor, for example, could have a profound effect on the efficiency and selectivity of delivery of the agent to the tumor.

ICAM-1 antisense oligodeoxynucleotide improves islet allograft survival and function.

Expression of intercellular adhesion molecule-1 (ICAM-1) and its ligand, leukocyte function antigen-1 (LFA-1), after pancreatic islet transplantation may affect both nonspecific and alloantigen-specific phases of graft destruction. We examined the effects of ICAM-1/LFA-1 blockade on the survival of islet allografts. Fresh C57BL/10 (H2h) pancreatic islets were transplanted under the renal subcapsular space (KC) or embolized into the liver after portal vein (PV) injection to C3H (H2k) mice. Recipients remained untreated or were treated for 7 days by i.p. administration of: ICAM-1 antisense phosphorothioate oligodeoxynucleotide (oligo) alone; anti-1CAM-1 (alphaICAM-1) monoclonal antibody (mAb) alone: alphaLFA-1 mAb alone; ICAM-1 oligo/alphaLFA mAb combination; alphaICAM-1 mAb/alphaLFA-1 mAb combination; or control oligo IP-8997 or IP-1082. In some experiments, donors were pretreated with ICAM-1 oligo. Inhibition of single ligand with 5.0 mg/kg ICAM-1 oligo (25.1 +/- 10.3), 100 microg/daily alphaICAM-1 mAb (24.2 +/- 8.0 days), or 50 microg/daily alphaLFA-1 mAb (42.8 +/- 25.9 days) prolonged the survivals of KC islet allografts in comparison with untreated controls (11.9 +/- 1.0 days; all p < 0.01). However, dual ICAM-1/LFA-1 blockade with either ICAM-1 oligo/alphaLFA-1 mAb (78.3 +/- 16.5 days) or (alphaICAM-1 mAb/aLFA-1 mAb (65.2 +/- 31.3 days) was the most effective therapy. Although pretreatment of donors with ICAM-1 oligo alone was ineffective (12.2 +/- 0.8 days; NS), a combination of donor pretreatment and recipient treatment started 1 day prior to grafting with ICAM-1 oligo (39.2 +/- 14.0 days) was more effective than the recipient treatment alone (24.6 +/- 8.8 days). Furthermore, ICAM-1/LFA-1 blockade improved islet function as evaluated by glucose tolerance test, and decreased inflammation in comparison with untreated controls. Similar in vivo results were obtained following PV administration of islet allografts. Thus, ICAM-1/LFA-1 blockade prolongs the survival of pancreatic islet allografts and improves their early function.

Covalent protein adducts of hydroquinone in tissues from rats: quantitation of sulfhydryl-bound forms following single gavage or intraperitoneal administration or repetitive gavage administration.

The current studies were conducted to investigate the degree and type of protein binding of hydroquinone (HQ) in the rat following single oral or intraperitoneal (ip) or repeated oral administrations. Male or female F-344 rats or male SD rats received a single dose of HQ at 0, 25, 50, or 100 mg/kg by either gavage or ip injection (SD rats only). In addition, male or female F-344 or male SD rats received HQ by gavage for 6 weeks (5 days/week) at 0, 25, or 50 mg/kg/day. Sulfhydryl-bound HQ was quantitated in protein from blood, kidneys, livers, or spleens 24 h after treatment using an alkaline permethylation procedure. The amount of total protein-S adducts increased with increasing dose in all the tissues that were assayed. Female rats had higher levels of adducts in blood, livers, and kidneys than did male rats when they were treated orally. Male F-344 rats treated orally had elevated levels of adducts in these same tissues compared to SD rats treated orally. For all genders and strains of rats and for all treatment regimens, mono-adducts predominated in livers (>72% of total). In the kidneys, tri- and tetrasubstituted adducts predominated with the summation accounting for >60% of the total. Ip administration of HQ resulted in significantly elevated levels of adducts in all the tissues that were examined, with the greatest increases seen for protein from blood and spleens. Levels of protein-S adducts of HQ in rat kidney following a single gavage administration correlated well with previously published differences in acute HQ nephrotoxicity in rats (female F-344 rat > male F-344 rat > male SD rat). Elevated levels of HQ protein-S adducts following repeated gavage administration did not correlate to measurable clinical signs of nephrotoxicity. Evidence is presented suggesting a possible role for the prostaglandin H synthase complex in the metabolic activation of HQ. In addition, protein arylation alone cannot account for the greater sensitivity of male F-344 rats toward chronic administration of HQ. The sensitivity of male F-344 rats to HQ is likely due to other factors, including the incidence and severity of chronic progressive nephropathy.

The in vivo and in vitro effects of exogenous leptin on ovulation in the rat.

Leptin, a hormonal product of the Lep gene, is expressed by adipocytes and is thought to play a role in regulating food intake and reproduction. The leptin protein has been localized in many reproductive tissues, including the ovary. Several publications indicate that the ovary is directly affected by leptin and that leptin may be a factor linking obesity and reproductive dysfunction. In this study, the effect of systemic leptin administration on ovulation in the rat ovary, both in vivo and in vitro, was investigated. Ip administration of leptin (30 microg at 3 hourly intervals for 15 h) to immature gonadotropin-primed rats caused a decline in ovulation in vivo, from 15.9+/-2.0 oocytes in the control animals to 5.3+/-1.6 oocytes in the leptin-treated animals (P < 0.001). Plasma progesterone and estradiol levels were analyzed immediately before ovulation, and neither was altered significantly in animals receiving the leptin treatment. Food consumption and body weight decreased following leptin treatment; however, a loss in body weight alone (pair-fed controls) was insufficient to explain the decrease in ovulation observed in the leptin-treated animals. In vitro perfusion of FSH-primed whole ovaries showed that treatment with leptin in combination with LH significantly decreased ovulations from 5.7+/-1.6 per ovary perfused with LH alone to 1.3+/-0.6 in those with LH and 1 microg/ml leptin (P < 0.05). Progesterone and estradiol levels in the samples taken during the perfusion period were unaffected by leptin treatment. In summary, leptin administration resulted in fewer ovulations, both in vivo and in vitro, but did not influence steroid levels. Systemic leptin administration at these doses can therefore inhibit ovulation, a process that occurs through a direct effect on the ovary.

The in Vivo and in Vitro Effects of Exogenous Leptin on Ovulation in the Rat

Leptin, a hormonal product of the Lep gene, is expressed by adipocytes and is thought to play a role in regulating food intake and reproduction. The leptin protein has been localized in many reproductive tissues, including the ovary. Several publications indicate that the ovary is directly affected by leptin and that leptin may be a factor linking obesity and reproductive dysfunction. In this study, the effect of systemic leptin administration on ovulation in the rat ovary, both in vivo and in vitro, was investigated. Ip administration of leptin (30 μg at 3 hourly intervals for 15 h) to immature gonadotropin-primed rats caused a decline in ovulation in vivo, from 15.9 ± 2.0 oocytes in the control animals to 5.3 ± 1.6 oocytes in the leptin-treated animals (P < 0.001). Plasma progesterone and estradiol levels were analyzed immediately before ovulation, and neither was altered significantly in animals receiving the leptin treatment. Food consumption and body weight decreased following leptin treatment; however, a loss in body weight alone (pair-fed controls) was insufficient to explain the decrease in ovulation observed in the leptin-treated animals. In vitro perfusion of FSH-primed whole ovaries showed that treatment with leptin in combination with LH significantly decreased ovulations from 5.7 ± 1.6 per ovary perfused with LH alone to 1.3 ± 0.6 in those with LH and 1 μg/ml leptin (P < 0.05). Progesterone and estradiol levels in the samples taken during the perfusion period were unaffected by leptin treatment. In summary, leptin administration resulted in fewer ovulations, both in vivo and in vitro, but did not influence steroid levels. Systemic leptin administration at these doses can therefore inhibit ovulation, a process that occurs through a direct effect on the ovary.

Anticonvulsant Activity and Plasma Level of 2,3-Benzodiazepin-4-ones (CFMs) in Genetically Epilepsy-Prone Rats

DE SARRO G., M. RIZZO, C. SPAGNOLO, R. GITTO, A. DE SARRO, G. SCOTTO, M. ZAPPALA AND A. CHIMIRRI. Anticonvulsant activity and plasma level of 2,3-benzodiazepin-4-ones (CFMs) in genetically epilepsy-prone rats. PHARMACOL BIOCHEM BEHAV 63 (4), 621–627, 1999.—Anticonvulsant properties of some 2,3-benzodiazepine derivatives acting as α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) antagonists have been examined in vivo in the genetically epilepsy-prone rats using an audiogenic seizures assay. 2,3-Benzodiazepin-4-ones (CFMs) are nonselective AMPA antagonists that have been found to be potent anticonvulsant compound is in acute models of epilepsy. Because very little is known about their actions in a chronic model of epilepsy, and no correlations exist between anticonvulsant potency and plasma levels of these derivatives, we planned to investigate such a relationship. Maximal anticonvulsant protection occurred 15–60 min after the IP administration of GYKI 52466, 30–90 min after CFM-2, and 45–120 min after CFM-3. In addition, maximal anticonvulsant effect was observed 60–120 min after the IP administration of CFM-4 and at 90 min after CFM-5. The therapeutic index revealed that GYKI 52466 was slightly more toxic than CFM-2 and CFM-3. The time course of plasma levels of rats treated showed that peak plasma concentration was observed 45 min after IP administration of CFM-2 and CFM-3 and 75 min after CFM-4 and CFM-5. Following IP administration of CFM-3 two curves were detected, one is referred to the injected compound, and the other to its demethylated metabolite, which corresponds to CFM-2. Also, for the nitroderivative CFM-4 two curves were detected: one of an injected compound and the second due to its reduced metabolite (CFM-2). Finally, three different metabolites were detected in rat plasma after IP administration of CFM-5. The present study demonstrated that CFMs showed a significant protection against auditory stimulation during the period of peak plasma concentrations, suggesting a marked inhibition of those brain structures involved in the initiation and/or spreading of the audiogenic seizures.

Lead-Induced Decrements in Waiting Behavior: Involvement of D 2-Like Dopamine Receptors

Some behavioral changes produced by chronic postweaning lead (Pb) exposure have been linked to mesolimbic dopamine (DA) system alterations. This study sought to determine the role of DA systems in Pb-induced changes in a fixed ratio (FR) waiting-for-reward paradigm. Rats exposed chronically from weaning to 0, 50, or 150 ppm Pb acetate drinking solutions earned free reinforcers for waiting after completion of an FR, with increasing time between successive free reinforcers. Responses during the waiting period reset the FR requirement. Once performance stabilized, the effects of acute IP administration of the D 1 agonist SKF82958, the D 2 agonist quinpirole, the D 1 antagonist SCH23390, and the D 2 antagonist eticlopride were determined. Pb itself increased FR response rates and decreased mean waiting time, a pattern of behavior that increased the number of earned reinforcers, but doubled the number of responses/reinforcer. None of the DA compounds mimicked Pb effects when administered to controls. Only DA agonists altered waiting behavior and responses per reinforcer. Quinpirole, in particular, appeared to reverse Pb effects on the FR wait baseline by increasing waiting time and decreasing FR resets to control levels. These findings point to a particular role for D 2 DA function in Pb’s detrimental effects on waiting.

Comparison of the Effects of the Selective Serotonin-Reuptake Inhibitors Fluoxetine, Paroxetine, Citalopram and Fluvoxamine in Alcohol-Preferring cAA Rats

Clinical studies indicate that selective serotonin-reuptake inhibitors (SSRIs) may decrease alcohol intake and craving in particular subgroups of alcoholics. The aim of the present study was to compare the behavioral profile of various SSRIs in alcohol-preferring cAA rats, a genetic model of alcoholism. The effects of acute IP administration of fluoxetine (doses in mg/kg 1–10), citalopram (3–30), fluvoxamine (3–30) and paroxetine (1–10) on ethanol (EtOH) intake and preference, as well as food and total fluid intake, were determined in a 12-h access, water vs. 10% v/v EtOH two-bottle choice paradigm. Each compound reduced EtOH intake [Minimal Effective Doses (MEDs) 5, 10, 30 and 1 mg/kg for fluoxetine, citalopram, fluvoxamine, and paroxetine, respectively]. The degree of selectivity, that is, the extent to which reductions in EtOH intake could be separated from reductions in food and/or total fluid intake varied across the compounds. Thus, whereas EtOH intake was more markedly affected than food intake by fluoxetine, both parameters were equally affected by citalopram, and food intake was more markedly affected than EtOH intake by fluvoxamine and paroxetine. The anti-alcohol effect also differed with respect to specificity, that is, the degree to which effects on EtOH intake coincided with effects on EtOH preference. Whereas fluoxetine showed the highest level of specificity, followed by citalopram and fluvoxamine, the effect of paroxetine was nonspecific. The observed variation in the degree of selectivity and specificity of the anti-alcohol effect of SSRIs suggests that reductions in EtOH intake are not merely a consequence of a general suppressive effect on consummatory behavior. It is hypothesized that differences between the behavioral profiles of these compounds reflect a differential involvement of 5-HT receptor subtypes.

Cardioprotective Effect of the Ischemic Preconditioning: Its Relation to Activation of Protein Kinase C

Background:We tested recent evidences that IP triggers selective activation of protein kinase C (PKC isozymes using isolated Langendorff-perfused rabbit heart with PKC activator, phorbol ester (PMA, 0.01 nM or inhibitor (calphostin C, 200 nM. Methods:After stabilization of baseline hemodynamics, the hearts were subjected to 45 min global ischemia (Ⅰ followed by 120 min reperfusion (R with IP (IP group, n=18 or without IP (ischemic control group, n=16. IP was induced by single episode of 5 min Ⅰ and 10 min R. In the PMA-treated group (n=19 and calphostin C-treated preconditioned group (n=15, PMA and calphostin C was given for 5 and 15 min before 45 min Ⅰ, respectively. Myocardial cytosolic and membrane PKC activities were measured by 32P-γ-ATP incorporation into PKC-specific pepetide;PKC isozymes were analyzed by Western blot with monoclonal antibodies. Results:IP significantly increased the recovery of the LV function including LVDP and coronary flow (p<0.05; however, enhancement of the functional recovery disappeared by calphostin C or PMA treatment. Cytosolic PKC activity decreased to 82-76% in the IP and PMA-treated group (p<0.05; membrane PKC activity increased to 218-272% (p<0.01. However, both fraction of PKC activity was not changed in the calphostin C-treated preconditioned group. In addition, Western blot revealed that PKC-α and e, especially e, were selectively translocated during subsequent sustained ischemia after IP or PMA administration. IP and PMA also reduced infarct size (frim 38 to 10-20%, p<0.05. However, calphostin C blocked infarct reduction effect of IP. Conclusion:These results indicate that in isolated rabbit heart model, cardioprotective effect of IP may be related, at least in part, to trigger selective translocation of PKC, especially e isotype. (Korean Circulation J 1999;29(6 :602-611

Antinociception, Tolerance, and Physical Dependence Comparison Between Morphine and Tramadol

The mechanism of action of tramadol includes the activation of opioid receptors, and the potential ability of the drug to induce tolerance and physical dependence has been evaluated in different animal species and humans. This work was designed to study the involvement of opioid receptors in the antinociceptive activity and the potential ability to develop tolerance, crosstolerance, and/or physical dependence of tramadol. The writhes induced by acetic acid administration was used as algesiometric test. After chronic administration of tramadol, tolerance was evaluated by measuring the antinociceptive activity, and physical dependence was measured by naloxone administration. Morphine was used as drug of comparison. The IP administration of tramadol produced a dose-dependent antinociception with an ED 50 value of 7.82 ± 1.16 mg/kg, which was unchanged after chronic administration of either tramadol (39.1 or 100 mg/kg) or morphine (1.05 or 100 mg/kg). By contrast, the ED 50 for morphine (0.21 ± 0.08 mg/kg) was significantly reduced only by chronic pretreatment with both doses of morphine (tolerance). Physical dependence was developed only in mice pretreated with morphine, as evidenced by the presence of jumps, wet-dog shakes, tachypnea, piloerection, seizures, diarrhea, and urination after the administration of naloxone (1 mg/kg). These findings suggest that the antinociceptive activity of tramadol in mice is due to activation of opioid and nonopioid mechanisms, and as opposed to morphine, is not likely to induce tolerance and physical dependence.

Relationship Between Anticonvulsant Activity and Plasma Level of Some 2,3-Benzodiazepines in Genetically Epilepsy-Prone Rats

DE SARRO, G. M. RIZZO, V. A. SINOPOLI, R. GITTO, A. DE SARRO, M. ZAPPALA AND A. CHIMIRRI. Relationship between anticonvulsant activity and plasma level of some 2,3-benzodiazepines in genetically epilepsy-prone rats. PHARMACOL BIOCHEM BEHAV 61(3) 215–220, 1998.—The anticonvulsant effects of some novel 2,3-benzodiazepines acting as α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid/kainate (AMPA/KA) antagonists were evaluated in genetically epilepsy prone rats. The ED 50 values against clonic and tonic seizures (in μmol/kg) revealed that the rank order of anticonvulsant activity was: GYKI 52466 > 2,3BZ-2 > 2,3 MBZ-2 > NBQX. Maximal anticonvulsant protection was observed 15–45 min after the IP administration of NBQX and GYKI 52466, 30–90 min after the IP administration of 2,3BZ-2, and 45–120 min after the IP administration of 2,3MBZ-2. The time course of plasma levels of rats treated with GYKI 52466 showed that peak plasma concentration was observed 15 min after IP administration, 2,3BZ-2 revealed that peak plasma concentration was achieved 45 min after IP administration, whereas following 2,3MBZ-2 administered IP, two curves were detected; one is referred to the parent compound and the other to its demethylate metabolite that corresponds to 2,3BZ-2. The therapeutic index (ratio of TD 50 values for impaired rotarod performance and ED 50 values for anticonvulsant activity) revealed that NBQX and GYKI 52466 were slighly more toxic than 2,3BZ-2 and 2,3MBZ-2. The present data suggest that 2,3-benzodiazepines acting at AMPA/kainate receptors play an important role in the generation and/or propagation of the audiogenic seizures in genetically epilepsy-prone rats.

Effect of intra-articular versus systemic anti-inflammatory drugs in a rabbit model of temporomandibular joint inflammation

Purpose: In an attempt to better understand the time course of inflammatory mediator production or release in inflammatory joint disease, a rabbit model of acute temporomandibular joint (TMJ) inflammation was established. This model was used to evaluate the effects of specific anti-inflammatory agents administered either systemically (intraperitoneal, IP) or locally (intra-articular, IA) on the modulation of in vivo tissue levels of two prototypic inflammatory mediators, prostaglandin E 2 (PGE 2) and bradykinin (BK). Materials and Methods: An experimental model of inflammation was created by administering carrageenan (carra) into one joint and an equivalent volume of saline (control) into the contralateral joint of 42 male New Zealand White rabbits. The development of hyperthermia was assessed by placement of a microthermister probe into the joint space. The inflammatory mediators, immunoreactive PGE 2 (iPGE 2) and BK (iBK), were recovered with microdialysis probes, and samples were assayed in conjunction with specific pharmacologic interventions. In the first part of the study, the time course for the release or production of iBK and iPGE 2 was determined. In the second part, the effects of IP versus IA administration of dexamethasone and a nonsteroidal anti-inflammatory drug, ketorolac tromethamine, were compared. Dexamethasone and ketorolac were administered at 3 hours and 1 hour, respectively, before the peak release of the inflammatory mediators. Results: The onset of IA hyperthermia, an index of inflammation, was evident by 90 minutes post-carra and reached a maximum of 1.2 °C above core temperature by 150 minutes post-carra. Intra-articular levels of iPGE 2 and iBK peaked at 240 minutes (3.35 ± 1.9 nmol/L) and 270 minutes (0.45 ± 0.29 nmol/L), respectively, after the induction of inflammation in the superior joint space. iBK levels within the superior joint space were significantly decreased by dexamethasone and ketorolac. Ketorolac (50 μg) decreased iBK and iPGE 2 levels when given IA or IP. With dexamethasone (3 mg), the levels of iBK were significantly reduced, and iPGE 2 levels were not changed. Conclusions: This study shows that the rabbit model of TMJ inflammation, with concurrent collection of iBK and iPGE 2 via microdialysis, is a reproducible and reliable method to investigate the time course of inflammatory mediator release and their modulation by either the local or systemic administration of anti-inflammatory medications.

Ethanol and negative feedback regulation of mesolimbic dopamine release in rats.

The objectives of this study were to examine the relationship between somatodendritic and terminal field dopamine (DA) release following manipulation of DA D2 receptors in the ventral tegmental area (VTA), systemic administration of ethanol, and inhibition of DA uptake in the nucleus accumbens (ACB). Perfusion of 5, 25 and 100 microM quinpirole (a D2 agonist), or sulpiride (a D2 antagonist) through the microdialysis probe in the VTA produced dose-related decreases or increases, respectively, in the extracellular levels of DA in both the VTA and ACB of adult Wistar rats. The IP administration of 2-3 g/kg ethanol produced a sustained increase in the extracellular levels of DA (150-200% of baseline) in the ACB for at least 2 h after injection, whereas only a transient increase was observed in the VTA. Local perfusion of the ACB with 100 microM GBR12909, a DA uptake inhibitor, elevated the extracellular levels of DA in the ACB to approximately 400% of baseline, but decreased the extracellular levels of DA in the VTA to approximately 50% of baseline. Overall, the results suggest that (a) there is an association between somatodendritic and terminal field DA release when D2 cell body autoreceptors in the VTA are manipulated, (b) elevating synaptic levels of DA in the terminal field activates a long-loop negative feedback system to the VTA, and (c) different mechanisms may be mediating the actions of ethanol on DA neuronal activity and terminal DA release.