Biomedical subjects

M A Moskowitz

Publications and source records attributed to M A Moskowitz.

At least 109 records · Page 6Linked to original sources

PubMed1998

Effects of nitric oxide synthase gene knockout on neurotransmitter release in vivo.

Nitric oxide serves as a diffusible messenger within the neuronal networks of the brain. Recent studies have suggested that nitric oxide may amplify neurotransmitter release via its ability to diffuse in a retrograde manner from postsynaptic to presynaptic neurons. Two isoforms of nitric oxide synthase may be present in neurons: Type I nitric oxide synthase (neuronal isoform) and Type III nitric oxide synthase (endothelial isoform). In this study, we examined the role of nitric oxide as an amplifier of neurotransmitter release by using K+ and N-methyl-D-aspartate stimulations via microdialysis probes located in cortex, striatum, and hippocampus. We compared responses obtained in wild-type mice versus knockout mice deficient in either neuronal isoform of nitric oxide synthase or endothelial isoform of nitric oxide synthase gene expression. No significant differences in glutamate and GABA release were observed between knockout mice and wild-type mice after K+ stimulations. In contrast, N-methyl-D-aspartate-stimulated glutamate release in cortex was significantly reduced in the neuronal NOS knockout mice, and N-methyl-D-aspartate-stimulated GABA release was significantly reduced in all brain regions of endothelial NOS knockout mice. These data suggest that the two nitric oxide synthase isoforms, most likely due to their specific neuronal localizations, may serve different roles in the modulation of excitatory versus inhibitory neurotransmission in mammalian brain.

Animals↗

PubMed1998

Mismatch between cerebral blood volume and flow index during transient focal ischemia studied with MRI and GD-BOPTA.

We investigated the regional and temporal changes in cerebral blood volume (CBV), cerebral blood flow (CBF), and vascular transit time in seven mongrel cats during 30 min transient focal ischemia, caused by occlusion of the middle cerebral artery. Dynamic susceptibility contrast magnetic resonance imaging was done at 4.7 T, using fast gradient echo T2* weighted imaging and intravenous injection of gadolinium-BOPTA/Dimeglumine. During occlusion, the areas showing a blood volume change were predominantly within the middle cerebral artery territory and could be divided into areas showing either CBV increases or decreases. The area with decreased blood volume also had decreased blood flow as measured by our flow-based index (p < 0.05) and was located in the central territory of the middle cerebral artery. Peripheral to this region was an area showing increased blood volume but without significant CBF changes (p > 0.05). During reperfusion, the CBF increased in the entire zone showing changes in blood volume during occlusion, and remained significantly elevated until 45 min post-occlusion, while CBV remained elevated in the hyperemic rim for at least 2 h. The presence of a peri-ischemic zone showing flow/volume mismatch identified a region wherein baseline CBF is maintained by means of compensatory vasodilatation, but where the ratio of CBF to CBV is decreased. Dynamic susceptibility contrast magnetic resonance imaging with gadolinium-BOPTA/Dimeglumine may be a valuable technique for the investigation of regional and temporal perturbations of hemodynamics during ischemia and reperfusion.

Animals↗

PubMed1998

Synergistic effects of caspase inhibitors and MK-801 in brain injury after transient focal cerebral ischaemia in mice.

1. Excitotoxic and apoptotic mechanisms have been implicated in the pathophysiology of cerebral ischaemia. Both MK-801, an NMDA receptor antagonist, or peptide inhibitors of the caspase family (z-VAD.FMK and z-DEVD.FMK), protect mouse brain from ischaemic cell damage. In this study, we examined whether these drugs which act via distinct mechanisms, afford even greater neuroprotection when given in combination following 2 h MCA occlusion (filament model) and 18 h reperfusion. 2. Given alone as pretreatment, MK-801 (1, 3 and 5 mg kg(-1), but not 0.3 mg kg(-1), i.p.) decreased infarct size by 34-75%. When injected 1 h after occlusion and before reperfusion, 3 mg kg(-1) reduced injury but not when administered I h after reperfusion. 3. Pretreatment with a subthreshold dose of MK-801 (0.3 mg kg(-1)) plus a subthreshold dose of z-VAD.FMK (27 ng) or z-DEVD (80 ng) significantly decreased infarct size by 29 and 30%, respectively, and enhanced neurological function. 4. Administering a subthreshold dose of z-VAD.FMK (27 ng) or z-DEVD.FMK (80 ng) as pretreatment extended the time window for MK-801 (3 mg kg(-1)) by 2 h from 1 h before reperfusion to at least 1 h after reperfusion. 5. Pretreating with a subthreshold dose of MK-801 (0.3 mg kg(-1)) extended the time window for z-DEVD.FMK (480 ng) from 1 h after reperfusion to at least 3 h after reperfusion. 6. We conclude that caspase inhibitors which putatively block apoptotic cell death and inhibit cytokine production and the NMDA antagonist MK-801 act synergistically and prolong their respective therapeutic windows in cerebral ischaemia.

Animals↗

PubMed1998

Relationships of gender and career motivation to medical faculty members' production of academic publications.

PURPOSE: To evaluate the relationships between both internal and external career-motivating factors and academic productivity (as measured by the total numbers of publications) among full-time medical faculty, and whether these relationships differ for men and women. METHOD: In 1995 a 177-item survey was mailed to 3,013 full-time faculty at 24 randomly selected U.S. medical schools stratified on area of medical specialization, length of service, and gender. Two-tailed t-tests and regression analyses were used to study the data. RESULTS: A total of 1,764 faculty were used in the final analyses. The women had published two thirds as many articles as had the men (mean, 24.2 vs. 37.8). Intrinsic and extrinsic career motivation were rated similarly (on a three-point scale) by the women and the men: intrinsic career motivation was rated higher (women's mean rating: 2.8, men's mean rating: 2.9) than was extrinsic career motivation (mean rating: 2.1 for both). The main findings of the regression analyses were (1) intrinsic career motivation was positively associated, and extrinsic career motivation was negatively associated, with the number of publications; (2) publication rates were higher for the men than for the women after controlling for career motivation; and (3) there was no significant effect of gender on these relationships. CONCLUSION: The women faculty published less than did their men colleagues, but this difference cannot be accounted for by gender differences in career motivation. Further research on institutional support, family obligations, harassment, and other factors that could affect academic productivity is necessary to understand the gender difference in numbers of publications.

Attitude of Health Personnel↗

PubMed1998

Junior faculty members' mentoring relationships and their professional development in U.S. medical schools.

PURPOSE: To determine (1) the prevalence of mentoring relationships for U.S. medical school junior faculty; (2) the quality of these mentoring relationships; (3) any variation by gender or race; and (4) the relationship between mentoring and junior faculty members' perceptions of institutional professional support; research-, teaching-, and clinical-skills development; allocation of time to professional activities; and career satisfaction. METHOD: In 1995 a 177-item survey was mailed to 3,013 full-time faculty at 24 randomly selected U.S. medical schools stratified on an area of medical specialization, graduation cohort, and gender. Mentoring was defined as "dynamic reciprocal relationship between an advanced career incumbent (the mentor) and a junior faculty member (the protégé) aimed at fostering the development of the junior person/protégé." Because mentoring is most crucial for junior faculty, the study focused on mentoring relationships within the previous three years ("recent mentoring") for faculty who were not full professors. Chisquare tests, analysis of variance, and principal-components analysis were used to analyze the data. RESULTS: In all, 1,808 (60%) of the 3,013 faculty surveyed, of whom 72% were junior faculty, returned completed questionaires. Fifty-four percent of the junior faculty had had a recent mentoring relationship. There was no significant difference between the men and the women faculty or between majority and minority faculty in the prevalence and quality of the mentoring relationships. The faculty with mentors rated their research preparation and research skills higher than did the faculty without mentors. Most of the women faculty (80%) and the minority faculty (86%) who had had mentors reported that it was not important to have a mentor of the same gender or minority group. CONCLUSION: Mentoring relationships are prevalent in academic medicine and should be promoted to support the career growth of junior faculty.

Faculty, Medical↗

PubMed1998

Attenuation of delayed neuronal death after mild focal ischemia in mice by inhibition of the caspase family.

Inhibitors of apoptosis and of excitotoxic cell death reduce brain damage after transient and permanent middle cerebral artery occlusion. We compared the neuroprotective effects of two caspase family inhibitors with the N-methyl-D-aspartate receptor antagonist (+)-MK-801 hydrogen maleate (MK-801) in a newly characterized cycloheximide-sensitive murine model of transient middle cerebral artery occlusion (30 minutes) in which apoptotic cell death is prominent. Ischemic infarction, undetected by 2,3,5-triphenyltetrazolium chloride staining at 24-hour reperfusion, featured prominently in the striatum at 72 hours and 7 days on hematoxylin-eosin-stained sections. Markers of apoptosis, such as oligonucleosomal DNA damage (laddering) and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL)-positive cells first appeared at 24 hours and increased significantly at 72 hours and 7 days after reperfusion. The TUNEL-labeled cells were mostly neurons and stained negative for glial (GFAP, glial fibrillary acid protein) and leukocyte specific markers (CD-45). The caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD.FMK; 120 ng intracerebroventricularly) or N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl ketone (z-DEVD.FMK; 480 ng intracerebroventricularly) decreased infarct size and neurologic deficits when administered 6 hours after reperfusion. The extent of protection was greater than in models of more prolonged ischemia or after permanent occlusion, and the therapeutic window was extended from 0 to 1 hours after 2-hour middle cerebral artery occlusion to at least 6 hours after brief ischemia. Also, z-VAD.FMK and z-DEVD.FMK treatment decreased oligonucleosomal DNA damage (DNA laddering) as assessed by quantitative autoradiography after gel electrophoresis. By contrast, MK-801 protected brain tissue only when given before ischemia (3 mg/kg intraperitoneally), but not at 3 or 6 hours after reperfusion. Despite a decrease in infarct size after MK-801 pretreatment, the amount of DNA laddering did not decrease 72 hours after reperfusion, thereby suggesting a mechanism distinct from inhibition of apoptosis. Hence, 30 minutes of reversible ischemia augments apoptotic cell death, which can be attenuated by delayed z-VAD.FMK and z-DEVD.FMK administration with preservation of neurologic function. By contrast, the therapeutic window for MK-801 does not extend beyond the time of occlusion, probably because its primary mechanism of action does not block the development of apoptotic cell death.

Amino Acid Chloromethyl Ketones↗

PubMed1998

Prolonged therapeutic window for ischemic brain damage caused by delayed caspase activation.

Apoptotic cell death is prominent in neurodegenerative disorders, such as Alzheimer's disease and Huntington's disease, and is found in cerebral ischemia. Using a murine model of delayed cell death, we determined that cleavage of zDEVD-amino-4-trifluoromethyl coumarin (zDEVD-afc) in brain homogenate, a measure of caspase activation, increased initially 9 hours after brief (30 minutes) middle cerebral artery occlusion along with caspase-3p20 immunoreactive cleavage product as determined by immunoblotting. zDEVD-afc cleavage activity was blocked by pretreatment or posttreatment with the caspase-inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl-ketone (zDEVD-fmk), and ischemic damage was reduced when the drug was injected up to 9 hours after reperfusion. The protection was long lasting (21 days). Hence, the period before caspase activation defined the therapeutic opportunity for this neuroprotective agent after mild ischemic brain injury. Prolonged protection after caspase inhibition plus the extended treatment window may be especially relevant to the treatment of neurodegenerative disorders.

Animals↗

PubMed1998

Physician variability and uncertainty in the management of breast cancer. Results from a factorial experiment.

OBJECTIVES: The purpose of this research was to determine the influence of patient and physician characteristics on physicians' level of variability and certainty in breast cancer care. METHODS: One hundred twenty-eight physicians viewed a videotape of a simulated physician-patient interaction in which the patient has an "atypical" breast lump. Six patient characteristics (age, race, socioeconomic status, physical mobility, comorbidity, presentation style) were manipulated experimentally, resulting in a balanced set of 32 different "patients." Physician subjects were recruited to fill four equal strata defined by specialty (surgeons versus nonsurgeons) and experience (< or = 15 or > 15 years since graduation from medical school). RESULTS: More than half of the physicians offered a diagnosis of benign breast disease, a third offered a diagnosis of breast cancer, and the rest believed that the patient had a normal breast or something "other." Results also indicated that physicians' level of certainty and test ordering behavior varied with the diagnosis that was offered. Of the six patient characteristics, only socioeconomic status influenced physician certainty; physicians were more certain of their diagnosis when the patient was of a higher socioeconomic status. Surgeons were found to be more certain of their diagnosis compared with nonsurgeons. However, surgeons were less likely to order radiologic tests or a tissue sample for metastatic evaluation than were nonsurgeons. CONCLUSIONS: Overall, physicians displayed considerable variability and uncertainty when diagnosing and managing possible breast cancer.

Adult↗

PubMed1998

Reducing random variation in reported rates of pressure ulcer development.

OBJECTIVES: The authors evaluated methods of reporting on rates of pressure ulcer development in long-term care to identify approaches that lead to more stable estimates of actual performance. METHODS: Performance measures for facilities that adequately adjust for both random variation and casemix should be relatively stable from one time period to the next. The authors calculated facility rates of pressure ulcer development over eight consecutive time periods and correlated measures over time using different reporting methods including z-scores, combining rates from several time periods, and limiting analyses to large facilities. Results were compared with a Monte Carlo simulation. RESULTS: Observed facility rates of pressure ulcer development varied considerably over time. The average correlation coefficient across seven time comparisons for observed rates was 0.17. Reporting performance as a z-score or limiting the analyses to large facilities increased the correlation. Combining two time periods was effective only when used with one of these other approaches. The correlation coefficient based on a simulation using only large facilities was 0.51. CONCLUSIONS: Random variation affects reported rates of pressure ulcer development. Using only large facilities and combining two time periods limits the effects of random variation and results in more stable estimates of performance. When describing performance, management must consider tradeoffs between having more accurate data, the frequency with which data are provided, and whether it is given to all providers.

Bias↗

PubMed1998

Profiling outcomes of ambulatory care: casemix affects perceived performance.

OBJECTIVES: The authors explored the role of casemix adjustment when profiling outcomes of ambulatory care. METHODS: The authors reviewed the medical records of 656 patients with hypertension, diabetes, or chronic obstructive pulmonary disease (COPD) receiving care at one of three Department of Veterans Affairs medical centers. Outcomes included measures of physiological control for hypertension and diabetes, and of exacerbations for COPD. Predictors of poor outcomes, including physical examination findings, symptoms, and comorbidities, were identified and entered into regression models. Observed minus expected performance was described for each site, both before and after casemix adjustment. RESULTS: Risk-adjustment models were developed that were clinically plausible and had good performance properties. Differences existed among the three sites in the severity of the patients being cared for. For example, the percentage of patients expected to have poor blood pressure control were 35% at site 1, 37% at site 2, and 44% at site 3 (P < 0.01). Casemix-adjusted measures of performance were different from unadjusted measures. Sites that were outliers (P < 0.05) with one approach had observed performance no different from expected with another approach. CONCLUSIONS: Casemix adjustment models can be developed for outpatient medical conditions. Sites differ in the severity of patients they treat, and adjusting for these differences can alter judgments of site performance. Casemix adjustment is necessary when profiling outpatient medical conditions.

Aged↗

PubMed1998

Neuronal NOS-cGMP-dependent ACh-induced relaxation in pial arterioles of endothelial NOS knockout mice.

We evaluated the effects of superfusing 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), eNOS null (B) an inhibitor of soluble guanylyl cyclase, and 7-nitroindazole sodium (7-NI), a selective neuronal nitric oxide synthase (nNOS) inhibitor, on the acetylcholine (ACh) response in endothelial NOS (eNOS) null mice. Pial arteriolar diameter was measured by intravital microscopy through a closed cranial window under alpha-chloralose anesthesia. NOS activity was measured by [3H]arginine-to-[3H]citrulline conversion in subjacent cortex in vitro. The density and distribution of muscarinic receptors in the brain were determined by quantitative [3H]quinuclidinyl benzilate autoradiography and did not differ between the eNOS mutants and wild-type mice. ACh superfusion (1 and 10 microM) dose dependently dilated pial arterioles in eNOS null and wild-type mice. ODQ (10 microM) attenuated ACh-induced dilation in both eNOS mutants (41% decrease at 10 microM ACh, P < 0.01, n = 6) and wild-type strains (n = 5 per group). By contrast, topical superfusion of 7-NI (100 microM) attenuated the ACh response in eNOS mutants only (66%, P < 0.05, and 25% decrease, P < 0.05, at 1 and 10 microM ACh, respectively). Our findings suggest that nNOS-guanosine 3',5'-cyclic monophosphate (cGMP)-dependent pathways dilate pial arterioles by compensatory mechanisms after eNOS gene disruption.

Acetylcholine↗

PubMed1998

YM872, a highly water-soluble AMPA receptor antagonist, preserves the hemodynamic penumbra and reduces brain injury after permanent focal ischemia in rats.

BACKGROUND AND PURPOSE: We recently described an image analysis technique based on the temporal correlation mapping (TCM) of injected contrast agents that can be used to distinguish the hemodynamic core and hemodynamic penumbra after focal ischemia. In this study we used this technique for the first time to investigate the effects of the water-soluble AMPA receptor antagonist YM872 in permanent focal ischemia. METHODS: Fischer 344 rats were subjected to permanent occlusion of the middle cerebral artery. Approximately 30 minutes after ischemia, functional CT images were collected with the use of a dynamic scanning protocol with bolus injections of nonionic contrast agent iohexol (1 mL/kg). TCM analysis defined the distributions of hemodynamic core and hemodynamic penumbra. Cerebral perfusion indices were calculated on the basis of the area under the first-pass transit curves. One hour after ischemia, animals were randomly treated with YM872 (n=8, 20 mg/kg per hour over 4 hours) or normal saline (n=10). Twenty-four hours later, neurological deficits were evaluated, and conventional CT and triphenyltetrazolium chloride staining were used to define volumes of ischemic damage. RESULTS: At 24 hours after ischemia, hypodense lesions were visible on conventional CT scans that were highly correlated with triphenyltetrazolium chloride lesion volumes. YM872 improved neurological deficits and reduced volumes of ischemic damage in cortex (90+/-14 versus 170+/-16 mm3 in controls) but not striatum (57+/-14 versus 79+/-6 mm3 in controls). Comparison of early TCM images with conventional CT scans of ischemic injury showed that the hemodynamic core was always damaged in all rats. In controls, 54% of the tissue within the hemodynamic penumbra evolved into ischemic damage compared with 24% in YM872-treated rats. Furthermore, the perfusion index corresponding to the ischemic damage threshold was significantly reduced by YM872 (28+/-2% versus 37+/-2% in controls). CONCLUSIONS: These results indicate that YM872 is a neuroprotective compound that ameliorates the deterioration of the hemodynamic penumbra after focal ischemia.

Animals↗

PubMed1998

Problems in assessing diabetes control in an ambulatory setting.

Problems in using medical records to assess outcomes of diabetes care have not been well defined. We reviewed the medical records of 288 patients with diabetes receiving ambulatory care over a 2-year period. We determined the availability of different tests of glycemic control and described site performance as the percentage of patients with a blood glucose exceeding either 180 or 240 mg/dl. Glycosylated hemoglobin determinations were performed in only 26.7% of patients. A blood glucose was available in 208 patients (72.2%) during a 6-month outcome period. For almost 50% of the sample, the glucose was greater than 180 mg/dl, whereas in 20% it exceeded 240 mg/dl. Judgments of whether sites differed in performance depended on how control was defined. Using a single glucose determination and a threshold of 180 mg/dl, similar fractions of patients were poorly controlled at each site (51.2 versus 45.0 versus 47.0%) (P = 0.75). At 240 mg/dl, although, one site performed much worse than the other two (14.6 versus 16.7 versus 31.8%) (P = 0.02). These results highlight difficulties in defining the outcome measure when using medical records to evaluate quality of care.

Aged↗

PubMed1998

Evaluation of complication rates after coronary artery bypass surgery using administrative data.

Our objectives were (1) to determine if studying hospital complication rates after coronary artery bypass graft (CABG) surgery provides information not available when only mortality is studied, and (2) to reexplore the utility of ICD-9-CM administrative data for CABG outcomes assessment. Using data from Massachusetts, we identified CABG cohorts from 1990 and 1992 to respectively develop and validate multivariate risk adjustment models predicting in-hospital mortality and complications. The resulting models had good discrimination and calibration. In 1992, adjusted hospital complication rates ranged widely from 13.0% to 57.6%, while mortality rates ranged from 1.4% to 6.1%. Hospitals with high complication rates tended to have high mortality (r = 0.74, p = 0.006), but 2 of the 12 hospitals studied ranked quite differently when judged by complications rather than mortality. We conclude that (1) complications after CABG occur frequently and may provide information about hospital quality beyond that obtained from hospital mortality rates, and that (2) administrative data continue to be a promising resource for outcomes research.

Aged↗

PubMed1997

Reduced fertility and postischaemic brain injury in mice deficient in cytosolic phospholipase A2.

Phospholipase A2 (PLA2) enzymes are critical regulators of prostaglandin and leukotriene synthesis and can directly modify the composition of cellular membranes. PLA2 enzymes release fatty acids and lysophospholipids, including the precursor of platelet-activating factor, PAF, from phospholipids. Free fatty acids, eicosanoids, lysophospholipids and PAF are potent regulators of inflammation, reproduction and neurotoxicity. The physiological roles of the various forms of PLA2 are not well defined. The cytosolic form, cPLA2, preferentially releases arachidonic acid from phospholipids and is regulated by changes in intracellular calcium concentration. We have now created 'knockout' (cPLA2-/-) mice that lack this enzyme, in order to evaluate its physiological importance. We find that cPLA2-/- mice develop normally, but that the females produce only small litters in which the pups are usually dead. Stimulated peritoneal macrophages from cPLA2-/- animals did not produce prostaglandin E2 or leukotriene B4 or C4. After transient middle cerebral artery occlusion, cPLA2-/- mice had smaller infarcts and developed less brain oedema and fewer neurological deficits. Thus cPLA2 is important for macrophage production of inflammatory mediators, fertility, and in the pathophysiology of neuronal death after transient focal cerebral ischaemia.

Animals↗

PubMed1997

Alteration of protein kinase C activity after transient focal cerebral ischemia in mice using in vitro [3H]phorbol-12,13-dibutyrate binding autoradiography.

Changes in the regional distribution of protein kinase C (PKC) after transient focal cerebral ischemia in SV-129 mice were assessed by quantitative autoradiography using [3H]phorbol-12,13-dibutyrate ([3H]PDBu) binding. [3H]PDBu binding did not change up to 10 min after reperfusion of 3 h ischemia, but at 1 h after reperfusion markedly decreased to 40-50% of control (pre-ischemia) in the ipsilateral striatum and the middle cerebral artery (MCA) region of cortex in SV-129 mice. The binding decreased to 20% of control at 3-7 days after reperfusion, but did not change in the ipsilateral anterior cerebral artery (ACA) territory or the contralateral brain. In the ipsilateral substantia nigra, which lies outside the ischemic zone, [3H]PDBu binding was not significantly changed compared to the control values (pre-ischemia) at early phase (up to 3 h after reperfusion), but marked reduction of the binding was observed 1 day after reperfusion. After 3 h ischemia followed by 3 h reperfusion, the morphological damage and the decrease in [3H]PDBu binding in the ipsilateral striatum and the MCA region of cortex was smaller in mice lacking the expression of neuronal nitric oxide synthase (type I NOS) gene mutant mice compared to wild-type (SV-129 and C57black/6) mice. Our data suggest that postischemic alterations of PKC binding activity were observed in the ischemic and non-ischemic lesions in the mouse brain.

Animals↗

PubMed1997

The selectivity of MDL 74,721 in models of neurogenic versus vascular components of migraine.

MDL 74,721 (R)-2-(N1,N1-dipropylamino)-8-methylaminosulfonylmethyl-1,2,3,4-te trahydronaphthalene, a sulfonamidotetralin, has been found to exhibit a 10,000-fold greater potency in neurogenic versus vascular models of migraine. Sumatriptan, a relatively pure 5-HT1D/5-HT1B receptor agonist, also showed higher potency versus neurogenic inflammation. However, for sumatriptan the potency difference (100-fold) in the two pathophysiological models was less pronounced than seen for MDL 74,721. The affinity profile of MDL 74,721 at 5-HT1 receptor subtypes may in part explain its ability to differentiate these two physiological responses. MDL 74,721 demonstrated nanomolar affinity for 5-HT1A (12.7 +/- 0.3 nM) and 5-HT1D (41.3 +/- 10.9 nM) but considerably lower affinity for 5-HT1B receptors (> 1000 nM). Serotonin-like activity was seen in in vitro functional assays including inhibition of forskolin-stimulated cAMP accumulation in human 5-HT1D receptor-transfected fibroblasts or eliciting vasoconstriction in isolated human pial arteries. The intrinsic activity (relative to 5 - HT[E(Amax)]) and affinity (pD2) for the human cerebrovascular 5-HT receptors were: 5-HT (100%, 7.51 +/- 0.09), sumatriptan (94%, 6.85 +/- 0.1) and MDL 74,721 (66%, 5.70 +/- 0.23). In anaesthetised cats, treatment with MDL 74,721 resulted in a dose-related reduction in the percentage of carotid flow going through the arteriovenous anastomoses to the lungs, with an ED50 of 0.3 mg/kg i.v., the same as sumatriptan. However, in the guinea-pig neurogenic model, MDL 74,721 inhibited plasma protein extravasation with an ED50 of 0.023 microg/kg compared to 2.5 microg/kg for sumatriptan. MDL 74,721 was also effective in this model (in rats) after oral administration. In conclusion, MDL 74,721 demonstrates a preclinical profile consistent with anti-migraine efficacy. Its marked preference for inhibiting neurogenic inflammation makes this compound a useful tool for assessing the relative contribution of this pathophysiological mechanism to the human disease state.

Animals↗

PubMed1997

Mechanisms of reduced striatal NMDA excitotoxicity in type I nitric oxide synthase knock-out mice.

We investigated the role of neuronal (type I) nitric oxide synthase (nNOS) in NMDA-mediated excitotoxicity in wild-type (SV129 and C57BL/6J) and type I NOS knock-out (nNOS-/-) mice and examined its relationship to apoptosis. Excitotoxic lesions were produced by intrastriatal stereotactic NMDA microinjections (10-20 nmol). Lesion size was dose- and time-dependent, completely blocked by MK-801 pretreatment, and smaller in nNOS knock-out mice compared with wild-type littermates (nNOS+/+, 11.7 +/- 1.7 mm3; n = 8; nNOS-/-, 6. 4 +/- 1.8 mm3; n = 7). The density and distribution of striatal NMDA binding sites, determined by NMDA receptor autoradiography, did not differ between strains. Pharmacological inhibition of nNOS by 7-nitroindazole (50 mg/kg, i.p.) decreased NMDA lesion size by 32% in wild-type mice (n = 7). Neurochemical and immunohistochemical measurements of brain nitrotyrosine, a product of peroxynitrite formation, were increased markedly in wild-type but not in the nNOS-/- mice. Moreover, elevations in 2,3- and 2,5-dihydroxybenzoic acid levels were significantly reduced in the mutant striatum, as a measure of hydroxyl radical production. The importance of apoptosis to NMDA receptor-mediated toxicity was evaluated by DNA laddering and by quantitative histochemistry [terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) staining]. DNA laddering was first detected within lesioned tissue after 12-24 hr. TUNEL-positive cells were first observed at 12 hr, increased in number at 48 hr and 7 d, and were located predominantly in proximity to the lesion border. The density was significantly lower in nNOS-/- mice. Hence, oligonucleosomal DNA breakdown suggesting apoptosis develops as a late consequence of NMDA microinjection and is reduced in nNOS mutants. The mechanism of protection in nNOS-/- mice may relate to decreased oxygen free radical production and related NO reaction products and, in part, involves mechanisms of neuronal death associated with the delayed appearance of apoptosis.

Animals↗