Gary Pastor

The N-methyl-d-aspartate antagonists CGS 19755 and CPP reduce ischemic brain damage in gerbils

N-Methyl-D-aspartate (NMDA) antagonists reduce ischemic brain damage and associated hypermotility. Two potent, selective and competitive NMDA antagonists, cis-4-(phosphonomethyl)-2-piperidine-carboxylic acid (CGS 19755) and 4-(3-phosphonopropyl)-2-piperazine-carboxylic acid (CPP), were characterized in the gerbil ischemia model with respect to dose-response and time course effects. Both drugs were effective in reducing ischemia-induced hippocampal brain damage as well as hypermotility. In this model, CGS 19755 was more potent than CPP, and had protective effects when given after longer delays between ischemia and drug administration.

Fluorescently labeled mesenchymal stem cells (MSCs) maintain multilineage potential and can be detected following implantation into articular cartilage defects

Several studies have reported enhanced repair of damaged cartilage following implantation of mesenchymal stem cells (MSCs) into full-thickness cartilage defects suggesting that the cells in the repair tissue were derived from the implant. However, it cannot be excluded that the enhanced tissue repair is derived from host cells recruited to the defect in response to the implant, rather than the re-population of the tissue by the implanted MSCs. Our objective was to study the short-term fate of fluorescently labeled MSCs after implantation into full-thickness cartilage defects in vivo. The fluorescent dye used in our studies did not affect MSC viability or their ability to undergo osteogenic and chondrogenic differentiation in vitro. MSC gelatin constructs were implanted into full-thickness cartilage defects in goats. These cells retained the dye and were detectable by histology and flow cytometry. At intervals spanning 2 weeks post-implantation we observed gradual loss of implanted cells in the defect as well as fragments of gelatin sponge containing labeled MSCs in deep marrow spaces indicating fragmentation, dislodgement and passive migration. Fluorescent labeling enabled us to determine whether the implanted cells were lost during early time points after implantation as well as their spatial orientation throughout the defect. By determining the fate of implanted cells, new biomaterials could be engineered to correct undesirable characteristics. Testing of new biomaterials in short-term in vivo models would provide faster optimization for cell retention needed for successful, long-term cartilage regeneration.

Antinociceptive effects of baclofen and muscimol upon intraventricular administration

The effects of intraventricularly administered baclofen and muscimol were investigated on tail-flick responding and on vocalization and motor responses to nociceptive pinch. Baclofen (1 microgram) and muscimol (0.1 microgram) strongly reduced responding to pinch, particularly vocalization, without altering tail-flick responding. When given systemically, however, baclofen markedly attenuated tail-flick as well as pinch responding. Muscimol produced only weak antinociception by systemic administration, suggesting that it may have poor access to brain. At antinociceptive doses, i. vent. muscimol produced less apparent muscle relaxation than did baclofen. These results suggest that baclofens antinociceptive action may be mediated in part by a supraspinal, GABAergic substrate, in addition to a spinal component which may not directly involve GABA.

Characterization of motor activity patterns induced by N-methyl-D-aspartate antagonists in gerbils

A computerized motor activity data collection and analysis system is described. An example of the utilization of the Digiscan system is provided, in which motor activity patterns induced by three N-methyl-D-aspartate (NMDA) antagonists and the dissociative anesthetic, ketamine, are compared. All of these compounds produce a distinct pattern of motor activity characterized by an increase in distance traveled, movement time, speed and perimeter walking, with a decrease in vertical activity. Recently described links between NMDA and phencyclidine (PCP) binding sites may account for these findings. The utility of computerized motor activity apparatus is clearly demonstrated.

Delayed emergence of antidepressant efficacy following withdrawal in olfactory bulbectomized rats

Repeated antidepressant treatment attenuates the step-down passive avoidance deficit which is induced by olfactory bulbectomy in rats. Using a shuttlebox passive avoidance procedure, the effects of antidepressants were investigated after various drug withdrawal intervals. Imipramine, amitriptyline, doxepin, bupropion and mianserin were effective at 48 and usually 72 hours after withdrawal, but no significant attenuation of the deficit was seen 4 hours after withdrawal from any antidepressant tested. At least 4 to 7 days of imipramine treatment were required for efficacy. A high dose of d-amphetamine (5 mg/kg) produced similar results while tranylcypromine and haloperidol were inactive at all withdrawal intervals tested. The olfactory bulbectomy syndrome may reflect functional serotonin deficiency, which would be ameliorated through antidepressant-induced alterations in serotonin receptor sensitivity.

Effect of capsaicin on carrageenan-induced inflammation in rat pleurisy and exudate substance P level.

Injection of 2.5 mg of λ-carrageenan into the rat pleural cavity resulted in a time-dependent increase in pleural exudate substance P (SP) levels up to 24 hr. Synergistic increases in the exudate formation were observed when a sub-optimal quantity of carrageenan was injected with SP. Pre-treatment of rats with capsaicin at 50 and 100 mg/kg s.c. daily for one week prior to the induction of pleurisy blocked the increase in exudate volume and SP levels when compared to that normally detected after carrageenan injection. These results suggest that inhibition of SP production may improve inflammatory conditions.

Postynaptic dopamine agonist properties of TL-99 are revealed by yohimbine co-treatment

The claim that TL-99 (6,7-dihydroxy-2-dimethylaminotetralin hydrobromide) is a selective dopamine autoreceptor agonist relies partly upon indirect behavioral evidence, particularly the absence of stereotyped behavior in treated rats. The possibility was examined that concurrent alpha 2-adrenoceptor agonist properties of TL-99 could have masked postsynaptic dopamine agonist activity. Co-administration of yohimbine or piperoxan with a high dose of TL-99 (30 mg/kg) dramatically increased motor activity in reserpinized rats, whereas each drug by itself had no effect. Contralateral rotational behavior in 6-hydroxydopamine-lesioned rats resulted from combined treatment with yohimbine and a high dose of TL-99 (30 mg/kg) but appeared to be suppressed by concurrent flaccidity if TL-99 was given by itself. Yohimbine failed to alter the effects of 3-PPP (N-n-propyl-3-(3-hydroxyphenyl)-piperidine), another putative dopamine autoreceptor agonist, in either model of postsynaptic dopamine agonism. It is concluded that a concurrent behaviorally depressant action of TL-99, possibly alpha 2-agonism, masks the stimulation of postsynaptic dopamine receptors by high doses of TL-99.

CGS 8216, a benzodiazepine antagonist, reduces food intake in food-deprived rats

CGS 8216, a benzodiazepine receptor antagonist with weak inverse agonist properties, reduced food intake in food-deprived rats when administered orally or intraperitoneally at doses that antagonize diazepam. This effect was sustained when CGS 8216 was administered daily for five days, indicating no rapid tolerance to the anorectic effect. Ro 15-1788 did not reduce feeding when administered orally, and was active only at high intraperitoneal doses (54 and 100 mg/kg). CGS 9896, a close analog of CGS 8216 but a benzodiazepine partial agonist with anxiolytic properties, did not reduce food intake at doses as high as 100 mg/kg IP or PO. These results support prior suggestions that benzodiazepine receptors may modulate feeding behavior, and suggest that CGS 8216 may have appetite suppressant properties.

Effect of CGS 25019C and other LTB4 antagonists in the mouse ear edema and rat neutropenia models

The pro-inflammatory lipid mediator leukotriene B 4 (LTB4) is derived from arachidonic acid (AA) metabolism through the activation of the 5-1ipoxygenase enzyme [1, 2]. Increased levels of LTB4 have been detected in patients with a variety of inflammatory diseases [3]. It has thus been postulated that LTB 4 receptor antagonists may have unique anti-inflammatory activity. As a result of extensive research, reports of potent, orally active, and selective LTB 4 receptor antagonists have emerged as potential anti-inflammatory agents [4, 5]. We have identified novel basic aryl amidines as LTB4 receptor antagonists that block LTB4-induced neutrophil func: tions including C D l l b up-regulation, calcium influx, aggregation, chemotaxis, and degranulation [5, 6]. Here, we present evidence of in vivo activities of two potent LTB4 receptor antagonists, CGS 25019C (4-{5-{4(aminoiminomethyl)phenoxy}pentoxy}-3-methoxy-N,Nbis(1-methylethyl) (Z)-2-butenedioate (1:1)) and a structural analog, CGS 24426A, from this chemical series. The compounds were evaluated in the AAinduced ear edema model in mice and LTB4-induced neutropenia model in rats.