RESUMO
Activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors is implicated in the pathophysiology of traumatic brain injury. Here, the effects of mechanical injury on the voltage-dependent magnesium (Mg2+) block of NMDA currents in cultured rat cortical neurons were examined. Stretch-induced injury was found to reduce the Mg2+ blockade, resulting in significantly larger ionic currents and increases in intracellular free calcium (Ca2+) concentration after NMDA stimulation of injured neurons. The Mg2+ blockade was partially restored by increased extracellular Mg2+ concentration or by pretreatment with the protein kinase C inhibitor calphostin C. These findings could account for the secondary pathological changes associated with traumatic brain injury.
Assuntos
Córtex Cerebral/metabolismo , Magnésio/farmacologia , N-Metilaspartato/farmacologia , Neurônios/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Lesões Encefálicas/metabolismo , Cálcio/metabolismo , Células Cultivadas , Córtex Cerebral/citologia , Maleato de Dizocilpina/farmacologia , Inibidores Enzimáticos/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais da Membrana , Naftalenos/farmacologia , Neurônios/citologia , Técnicas de Patch-Clamp , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/efeitos dos fármacosRESUMO
Application of arachidonic acid or prostaglandin G(2) to the brain surface of anesthetized cats induced cerebral arteriolar damage. Scavengers of free oxygen radicals inhibited this damage. Prostaglandin H(2), prostaglandin E(2), and 11,14,17-eicosatrienoic acid did not produce arteriolar damage. It appears that increased prostaglandin synthesis produces cerebral vascular damage by generating free oxygen radicals.
Assuntos
Ácidos Araquidônicos/farmacologia , Artérias Cerebrais/efeitos dos fármacos , Hipertensão/patologia , Endoperóxidos de Prostaglandina/farmacologia , Prostaglandinas G/farmacologia , Animais , Arteríolas/efeitos dos fármacos , Arteríolas/patologia , Gatos , Artérias Cerebrais/patologia , Endotélio/efeitos dos fármacos , Endotélio/patologia , Prostaglandinas E/farmacologia , Prostaglandinas H/farmacologia , Vasodilatação/efeitos dos fármacosRESUMO
When human platelets are aggregated by thrombin, material is released that rapidly contracts strips of spirally cut porcine coronary artery. Prevention of the contraction by indomethacin suggested mediation by a prostaglandin. The contraction produced by aggregating platelets was unlike those produced by prostaglandins E2, F2alpha, G2, or H2, but resembled that evoked by thromboxane A2, which is formed by platelets during aggregation.
Assuntos
Circulação Coronária/efeitos dos fármacos , Hidroxiácidos/isolamento & purificação , Agregação Plaquetária , Prostaglandinas/sangue , Piranos/isolamento & purificação , Vasoconstritores , Artérias , Plaquetas/metabolismo , Humanos , Masculino , Contração Muscular/efeitos dos fármacos , Músculo Liso , Prostaglandinas/metabolismo , Prostaglandinas/farmacologiaRESUMO
Although prostaglandins E(2) and F(2alpha) have been suggested as mediators of the pulmonary hypertension seen after endotoxin infusion or during alveolar hypoxia, their precursors, the endoperoxides (prostaglandins G(2) and H(2)) are much more potent vasoconstrictors in vitro. In this study we compared the effects of prostaglandin (PG)H(2), a stable 9-methylene ether analogue of PGH(2) (PGH(2)-A), PGE(2), and PGF(2alpha) on pulmonary hemodynamics in awake sheep. The animals were prepared to allow for measurement of (a) lung lymph flow; (b) plasma and lymph protein concentration; (c) systemic and pulmonary vascular pressures; and (d) cardiac output. We also determined the effect of prolonged PGH(2)-A infusions on lung fluid balance and vascular permeability by indicator dilution methods, and by assessing the response of lung lymph. Both PGH(2) and PGH(2)-A caused a dose-related increase in pulmonary artery pressure: 0.25 mug/kg x min tripled pulmonary vascular resistance without substantially affecting systemic pressures. Both were 100 times more potent than PGE(2) or PGF(2alpha) in this preparation. PGH(2)-A, as our analysis of lung lymph and indicator dilution measurements show, does not increase the permeability of exchanging vessels in the lung to fluid and protein. It does, however, augment lung fluid transport by increasing hydrostatic pressure in the pulmonary circulation. We conclude: (a) that PGH(2) is likely to be an important mediator of pulmonary vasoconstriction; (b) its effects are probably not a result of its metabolites PGE(2) or PGF(2alpha).
Assuntos
Endoperóxidos Sintéticos de Prostaglandinas/farmacologia , Circulação Pulmonar/efeitos dos fármacos , Animais , Pressão Sanguínea/efeitos dos fármacos , Permeabilidade Capilar/efeitos dos fármacos , Pulmão/fisiologia , Linfa/efeitos dos fármacos , Prostaglandinas H/farmacologia , Ovinos , Resistência Vascular/efeitos dos fármacos , Vasoconstrição/efeitos dos fármacosRESUMO
Overactivation of ionotropic glutamate receptors has been implicated in the pathophysiology of traumatic brain injury. Using an in vitro cell injury model, we examined the effects of stretch-induced traumatic injury on the AMPA subtype of ionotropic glutamate receptors in cultured neonatal cortical neurons. Recordings made using the whole-cell patch-clamp technique revealed that a subpopulation of injured neurons exhibited an increased current in response to AMPA. The current-voltage relationship of these injured neurons showed an increased slope conductance but no change in reversal potential compared with uninjured neurons. Additionally, the EC(50) values of uninjured and injured neurons were nearly identical. Thus, current potentiation was not caused by changes in the voltage-dependence, ion selectivity, or apparent agonist affinity of the AMPA channel. AMPA-elicited current could also be fully inhibited by the application of selective AMPA receptor antagonists, thereby excluding the possibility that current potentiation in injured neurons was caused by the activation of other, nondesensitizing receptors. The difference in current densities between control and injured neurons was abolished when AMPA receptor desensitization was inhibited by the coapplication of AMPA and cyclothiazide or by the use of kainate as an agonist, suggesting that mechanical injury alters AMPA receptor desensitization. Reduction of AMPA receptor desensitization after brain injury would be expected to further exacerbate the effects of increased postinjury extracellular glutamate and contribute to trauma-related cell loss and dysfunctional synaptic information processing.
Assuntos
Lesões Encefálicas/fisiopatologia , Neocórtex/fisiologia , Neurônios/fisiologia , Células Piramidais/fisiologia , Receptores de AMPA/fisiologia , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/farmacologia , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Animais Recém-Nascidos , Benzodiazepinas/farmacologia , Técnicas de Cultura de Células/métodos , Células Cultivadas , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Modelos Neurológicos , Neocórtex/citologia , Neurônios/citologia , Neurônios/efeitos dos fármacos , Técnicas de Patch-Clamp , Células Piramidais/citologia , Células Piramidais/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/antagonistas & inibidores , Valores de ReferênciaRESUMO
Calcium influx and elevation of intracellular free calcium ([Ca2+]i), with subsequent activation of degradative enzymes, is hypothesized to cause cell injury and death after traumatic brain injury. We examined the effects of mild-to-severe stretch-induced traumatic injury on [Ca2+]i dynamics in cortical neurons cultured on silastic membranes. [Ca2+]i was rapidly elevated after injury, however, the increase was transient with neuronal [Ca2+]i returning to basal levels by 3 h after injury, except in the most severely injured cells. Despite a return of [Ca2+]i to basal levels, there were persistent alterations in calcium-mediated signal transduction through 24 h after injury. [Ca2+]i elevation in response to glutamate or NMDA was enhanced after injury. We also found novel alterations in intracellular calcium store-mediated signaling. Neuronal calcium stores failed to respond to a stimulus 15 min after injury and exhibited potentiated responses to stimuli at 3 and 24 h post-injury. Thus, changes in calcium-mediated cellular signaling may contribute to the pathology that is observed after traumatic brain injury.
Assuntos
Lesões Encefálicas/metabolismo , Sinalização do Cálcio , Córtex Cerebral/lesões , Córtex Cerebral/metabolismo , Neurônios/metabolismo , Animais , Cálcio/metabolismo , Células Cultivadas , Córtex Cerebral/citologia , Cicloleucina/análogos & derivados , Cicloleucina/farmacologia , Inibidores Enzimáticos/farmacologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Ácido Glutâmico/metabolismo , N-Metilaspartato/farmacologia , Neuroglia/citologia , Neuroglia/metabolismo , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Ratos , Ratos Sprague-Dawley , Tapsigargina/farmacologiaRESUMO
To determine the possible role that leukotrienes (LTs) may play in the regulation of cerebral blood flow, the responses of cerebral arterioles to LTs and 12-hydroxyeicosatetraenoic acid (12-HETE) were studied in vivo in rabbits equipped with a cranial window for direct observation of the microcirculation. Topical application of LTC4, LTD4, or 12-HETE (1.6 X 10(-9)-3.1 X 10(-6) M) neither constricted nor dilated the pial arteries. LTB4 produced only a 5% vasoconstriction at 3.0 X 10(-6) M. However, bradykinin induced dose-dependent arteriolar vasodilation and histamine and 5-hydroxytryptamine induced dose-dependent arteriolar vasoconstriction. Although some LTs have potent vasoconstrictor activity in peripheral tissues and 5-lipoxygenase products have been hypothesized to be mediators of vasospasm after subarachnoid hemorrhage, LTB4, LTC4, LTD4, and 12-HETE apparently are unable to induce significant constriction of the cerebral arterioles in the anesthetized rabbit.
Assuntos
Bradicinina/farmacologia , Artérias Cerebrais/efeitos dos fármacos , Circulação Cerebrovascular/efeitos dos fármacos , Histamina/farmacologia , Ácidos Hidroxieicosatetraenoicos/farmacologia , SRS-A/farmacologia , Serotonina/farmacologia , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico , Animais , Artérias/efeitos dos fármacos , Artérias Cerebrais/anatomia & histologia , Masculino , Microcirculação/efeitos dos fármacos , Pia-Máter/irrigação sanguínea , CoelhosRESUMO
Thimerosal causes synthesis and/or release of both endothelium-derived relaxing factor (EDRF) and prostaglandins from conductance vessels in vitro. We tested its effects and mechanism of action on mouse pial arterioles in vivo using intravital microscopic techniques. Topical thimerosal dilated pial arterioles. This effect was eliminated by endothelial injury produced by a laser/Evans blue technique. Dilation was also eliminated by topical L-NMMA, a reported inhibitor of EDRF synthesis. Topical thimerosal also reduced the incidence of platelet adhesion/aggregation ("capture") at a site of minimal endothelial damage. This effect was eliminated by L-NMMA pretreatment. The ability of thimerosal to dilate arterioles was eliminated not only by treatments thought to eliminate synthesis/release of EDRF, but also by cyclooxygenase inhibitors. However, inhibition of platelet adhesion/aggregation was not affected by cyclooxygenase inhibition. Thimerosal significantly increased production of prostaglandin E2 recovered from a closed cranial window. We conclude that the dilating effects of thimerosal on diameter require two endothelium-derived agents: EDRF and one or more prostaglandins acting in concert. However, the inhibiting effect of thimerosal on local platelet adhesion/aggregation appears to be caused only by an increase in EDRF at the injured site.
Assuntos
6-Cetoprostaglandina F1 alfa/farmacologia , Arteríolas/fisiologia , Dinoprostona/farmacologia , Óxido Nítrico/farmacologia , Pia-Máter/irrigação sanguínea , Timerosal/farmacologia , Animais , Arginina/análogos & derivados , Arginina/farmacologia , Masculino , Camundongos , Vasodilatação/efeitos dos fármacos , ômega-N-MetilargininaRESUMO
Effects of varying doses of troleandomycin (TAO) on methylprednisolone disposition were examined in five steroid-dependent asthmatic patients. The characteristic reduction in methylprednisolone elimination in the presence of TAO after a 40 mg IV methylprednisolone was also present after methylprednisolone doses as low as 4 mg. In patients receiving continuous TAO on an every-other-day basis, inhibition of methylprednisolone elimination was impaired to a greater extent on the "day on" TAO than on the "day off" TAO Methylprednisolone elimination on the day off TAO was still slower than that before TAO, however, TAO on a multiple-dose schedule resulted in greater reduction of methylprednisolone elimination than after a single TAO dose. These results suggest that TAO induces immediate and continued inhibition of methylprednisolone disposition.
Assuntos
Asma/tratamento farmacológico , Metilprednisolona/metabolismo , Troleandomicina/administração & dosagem , Relação Dose-Resposta a Droga , Interações Medicamentosas , Quimioterapia Combinada , Humanos , Cinética , Metilprednisolona/uso terapêutico , Fatores de Tempo , Troleandomicina/uso terapêuticoRESUMO
The pharmacokinetics of theophylline following intravenous injection of aminophylline, 4 mg/kg of body weight, were determined in 30 children with asthma and in 6 normal adult volunteers. The average total clearance of theophylline was 87 ml/hr/kg in the children and 57 ml/hr/kg in the adults. The biologic half-life of theophylline in the children ranged from 1.42 to 7.85 hours, reflecting mainly pronounced interindividual differences in the elimination rate constant of the drug. There was no significant difference between the children and adults with respect to the distribution rate constants and apparent volumes of distribution of theophylline, but the elimination rate constant of the drug was considerably higher in children than in adults. Thus, children eliminate theophylline more rapidly on the average than do adults and also show pronounced interindividual differences in the elimination of the drug. Compared to adults, children tend to require relatively larger amounts of theophylline per day and the doses may have to be given at shorter intervals of time.
Assuntos
Aminofilina/metabolismo , Asma/tratamento farmacológico , Adolescente , Adulto , Fatores Etários , Aminofilina/administração & dosagem , Aminofilina/uso terapêutico , Criança , Feminino , Meia-Vida , Humanos , Injeções Intravenosas , Cinética , Masculino , Taxa de Depuração MetabólicaRESUMO
Nucleotides are known to enhance cyclooxygenase product formation in several tissues and, in addition, are believed to function as cofactors for mammalian 5-lipoxygenases. Since nucleotides are released by stimulated platelets and by damaged tissue, we examined the hypothesis that nucleotides can affect the metabolism of arachidonic acid (AA) in washed human platelets. The various nucleotides were given 15 sec prior to the addition of 3 microM arachidonic acid and 1 muCi [3H]AA. We found that the phosphorylated adenine derivatives (ATP, ADP, and AMP) increased the formation of 12-hydroxyeicosatetraenoic acid (12-HETE) by 2-fold without altering the formation of cyclooxygenase products. Adenosine was without effect on 12-HETE formation. ATP also stimulated 12-HETE formation in lysed platelets. This suggests that the 12-lipoxygenase enzyme of platelets can be regulated by adenine nucleotides. We next determined the portion of the nucleotide molecule responsible for the enhanced 12-lipoxygenase activity of platelets. Alteration of the nucleotide base led to a decrease in stimulation, with GTP less active than ATP, and UTP even less active than GTP. Studies with adenine nucleotides showed that the length of the phosphate chain was not important. We also found that the stable methylene isosters of ATP (alpha, beta-methylene ATP and beta, gamma-methylene ATP) increased 12-HETE formation, suggesting that the conformation and hydrolysis of the phosphate chain are not responsible for the stimulatory activity. Cyclic 3',5'AMP and 3'AMP were inactive, implying the necessity for a free phosphate at the 5' position for nucleotide stimulation of 12-HETE synthesis. In conclusion, platelet 12-lipoxygenase was stimulated by ATP, as is true for several mammalian 5-lipoxygenases. However, cyclooxygenase product formation by platelets was not altered by nucleotide addition. These studies suggest that following in vivo injury or platelet aggregation, when local concentrations of nucleotides are high, platelet lipoxygenase activity may be stimulated.
Assuntos
Nucleotídeos de Adenina/farmacologia , Araquidonato 12-Lipoxigenase/sangue , Araquidonato Lipoxigenases/sangue , Ácidos Araquidônicos/sangue , Plaquetas/enzimologia , Prostaglandina-Endoperóxido Sintases/sangue , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico , Difosfato de Adenosina/farmacologia , Monofosfato de Adenosina/farmacologia , Trifosfato de Adenosina/farmacologia , Adulto , Ácido Araquidônico , Plaquetas/efeitos dos fármacos , Guanosina Trifosfato/farmacologia , Humanos , Ácidos Hidroxieicosatetraenoicos/sangue , Uridina Trifosfato/farmacologiaRESUMO
During secondary aggregation, platelets release 5-hydroxytryptamine (5-HT) from their dense granule stores concurrent with arachidonic acid (AA) metabolism. To examine the hypothesis that released 5-HT has a modulatory effect on the metabolism of AA by platelets, we incubated nonaggregating washed human platelets with 5-HT in the presence of [3H]AA. Stimulation with 10(-4) M 5-HT, followed by incubation with 3 microM AA and 1 microCi [3H]AA for 5 min, resulted in a decrease in the formation of thromboxane B2 (TxB2) and 12-hydroxyheptadecatrienoic acid (HHT, P less than 0.05). The same treatment conditions and stimulation with 10(-7) to 10(-4) M 5-HT resulted in an elevation of 12-hydroxyeicosatetraenoic acid (12-HETE) formation (P less than 0.05). Treatment with the monoamine uptake inhibitor imipramine (20 microM) further increased the stimulation of 12-HETE formation observed in the presence of 10(-4) M 5-HT, suggesting that 5-HT may act at the platelet surface. A 5-HT1A receptor agonist, 8-hydroxy-dipropylaminotetralin (DPAT, 10(-6) to 10(-4) M) stimulated the formation of platelet cyclooxygenase (CO) products, whereas (+/-)1-(2,5-dimethoxy-4-iodo phenyl)-amino propane hydrochloride (DOI, 10(-6) to 10(-4) M), a 5-HT2 receptor agonist, had no significant effect on CO product formation. In addition, the 5-HT2 receptor antagonist ketanserin (10(-7) M) did not block the changes in CO or lipoxygenase metabolism induced by 5-HT. Since both DOI and DPAT stimulated 12-HETE formation whereas ketanserin was unable to reverse the 5-HT-enhanced 12-HETE formation, it seems unlikely that the stimulation of a 5-HT2 receptor is responsible for this action of 5-HT on platelets. We conclude that 5-HT depresses CO product formation while increasing 12-HETE formation through interaction with a platelet serotonergic binding site other than the 5-HT2 receptor.
Assuntos
Ácidos Araquidônicos/metabolismo , Plaquetas/efeitos dos fármacos , Lipoxigenase/fisiologia , Prostaglandina-Endoperóxido Sintases/fisiologia , Serotonina/farmacologia , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico , 8-Hidroxi-2-(di-n-propilamino)tetralina , Adulto , Ácido Araquidônico , Plaquetas/metabolismo , Humanos , Ácidos Hidroxieicosatetraenoicos/metabolismo , Imipramina/farmacologia , Técnicas In Vitro , Receptores de Serotonina/efeitos dos fármacos , Tetra-Hidronaftalenos/farmacologiaRESUMO
The purpose of this study was to investigate whether anandamide induces cannabimimetic responses, mainly mobilization of arachidonic acid, in primary cultures of rat brain cortical astrocytes. Confluent monolayer cultures of astrocytes, prelabeled with [3H]arachidonic acid, were incubated with anandamide or delta9-tetrahydrocannabinol (delta9-THC) in the presence or absence of thimerosal, a fatty acid acyl CoA transferase inhibitor and phenylmethylsulfonyl fluoride, an amidohydrolase inhibitor. Anandamide and delta9-THC induced a time- and concentration-dependent release of arachidonic acid in the presence, but not in the absence, of thimerosal. Anandamide- and delta9-THC-stimulated arachidonic acid release was pertussis toxin-sensitive, indicating a receptor/G-protein involvement. A novel and selective cannabinoid receptor antagonist, SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4- methyl-1H-pyrazole-3-carboximide hydrochloride], blocked the arachidonic acid release, suggesting a cannabinoid receptor-mediated pathway. In astrocytes, the magnitude of anandamide-induced arachidonic acid release was equal to that released by equimolar concentrations of delta9-THC. Furthermore, direct assay of amidohydrolase activity indicated that degradation of anandamide into arachidonic acid and ethanolamine was negligible in cortical astrocytes. Our results suggest that anandamide stimulates receptor-mediated release of arachidonic acid, and the receptor may be the cannabinoid receptor. Astrocytes, containing a cannabinoid receptor and lower or negligible amidohydrolase activity, may be an important brain cell model in which to study the cannabimimetic effects of anandamide at a cellular and molecular level.
Assuntos
Ácido Araquidônico/metabolismo , Ácidos Araquidônicos/farmacologia , Canabinoides/farmacologia , Dronabinol/farmacologia , Piperidinas/farmacologia , Pirazóis/farmacologia , Amidoidrolases/fisiologia , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Células Cultivadas , Endocanabinoides , Toxina Pertussis , Alcamidas Poli-Insaturadas , Ratos , Rimonabanto , Fatores de Virulência de Bordetella/farmacologiaRESUMO
Traumatic brain injury causes alterations in cerebral blood flow that are thought to influence secondary pathophysiology and neurologic outcome in humans. Since it is difficult to study early changes in blood flow in head-injured patients, animal models of brain injury must be employed. However, techniques to monitor brain blood flow in animals are labor intensive and generally provide discontinuous flow measurements. The present study examines the application of laser-Doppler flowmetry for measurement of cerebral blood flow following experimental brain injury. This method allows continuous monitoring of local cerebral blood flow before, during, and after injury. Rats (n = 9) were prepared for lateral fluid percussion injury under barbiturate anesthesia. Injury (2.10 +/- 0.02 atm) was induced over the right parietal cortex, and blood flow was monitored in the contralateral cortex. Seconds after the peak hypertension after injury, blood flow in the left parietal cortex increased 226% +/- 18% (means +/- SEM). This increase was transient, with blood flow falling below control values within minutes. Five minutes after injury, blood flow was 83% +/- 8% of control, and at 1 h, this value had fallen to 56% +/- 6%. Blood flow at 60 min was 93% +/- 5% of control in the sham-injured group (n = 10). The reduction in cerebral blood flow in our laser-Doppler study was of similar magnitude as previously reported in rats injured at a similar intensity when blood flow was examined with radiolabeled microspheres. Given these results, we believe laser-Doppler flowmetry can be used to continuously monitor posttraumatic blood flow following experimental brain injury.
Assuntos
Lesões Encefálicas/fisiopatologia , Circulação Cerebrovascular/fisiologia , Animais , Pressão Sanguínea/fisiologia , Córtex Cerebral/irrigação sanguínea , Fluxometria por Laser-Doppler , Masculino , Microcirculação/fisiologia , Microesferas , Monitorização Fisiológica , Percussão , Ratos , Ratos Sprague-DawleyRESUMO
Oxygen free radicals, such as the superoxide anion, are known to mediate damage to the cerebral microcirculation following traumatic brain injury. The purpose of this study was to determine if superoxide dismutase (SOD), a scavenger of superoxide anion, could alter posttraumatic cortical blood flow. Following barbiturate anesthesia, rats were surgically prepared for moderate fluid percussion brain injury. Cortical blood flow contralateral to the site of injury was measured using laser-Doppler flowmetry. Laser-Doppler flowmetry assesses flow by measuring cell volume and velocity, which are multiplied electronically to give flow. Starting 10 min before injury, animals received either superoxide dismutase (24,000 U/kg bolus, followed by continuous infusion of 1600 U/kg/min) or an equal volume of saline. Blood pressure, heart rate, and cortical blood flow were measured up to 1 h posttrauma. Rats receiving superoxide dismutase had significantly higher cortical blood flow posttrauma (F = 6.91, p < 0.02). One hour posttrauma, the blood flow in SOD-treated rats was 89 +/- 8% of preinjury baseline, whereas this value was only 66 +/- 6% of control in saline-treated rats. SOD caused not only greater blood velocity but also less reduction in cortical blood volume after injury. There were no significant differences between the groups with respect to blood pressure or heart rate. This study further supports the role of oxygen radical-mediated cerebrovascular dysfunction following traumatic brain injury and is the first to show the beneficial effect of SOD on cortical blood flow following fluid percussion brain injury.
Assuntos
Lesões Encefálicas/fisiopatologia , Córtex Cerebral/irrigação sanguínea , Circulação Cerebrovascular/efeitos dos fármacos , Superóxido Dismutase/farmacologia , Animais , Velocidade do Fluxo Sanguíneo/efeitos dos fármacos , Volume Sanguíneo/efeitos dos fármacos , Fluxometria por Laser-Doppler , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
Polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) is being explored as an agent to reduce oxygen radical-mediated damage following brain injury. Yet little is known concerning the site of action of IV-administered PEG-SOD or the capacity of this conjugated enzyme to enter the brain. The purpose of this study was to determine the brain content of PEG-SOD in normal and fluid percussion injured rats. The fluid percussion device was attached over the right parietal cortex and a moderate (2.0 atm) intensity injury was produced. PEG-SOD was conjugated with 125I and given (2000 U/kg, 5 microCi/kg) to rats either 30 min before or 30 min after brain injury. Another group received [125I]PEG-SOD but was not injured. Plasma and left and right brain hemispheres were counted for [125I]PEG-SOD. Plasma levels of [125I]PEG-SOD declined similarly in all three groups during the 90-min period after IV administration. Brain [125I]PEG-SOD was low in control animals (0.034 U/g wet wt). In animals given PEG-SOD after injury the brain level was elevated sixfold in both the left and right hemispheres, compared to control. In rats given the drug before injury, [125I]PEG-SOD was 10 times control level in the right hemisphere, which is the side on which the injury device is attached, and 6 times control level in the left hemisphere. We conclude that traumatic brain injury produces an increase in brain PEG-SOD. The exact cellular site of the increased brain PEG-SOD remains to be clarified.
Assuntos
Lesões Encefálicas/metabolismo , Encéfalo/metabolismo , Polietilenoglicóis/farmacocinética , Superóxido Dismutase/farmacocinética , Animais , Gasometria , Pressão Sanguínea/fisiologia , Lesões Encefálicas/fisiopatologia , Injeções Intravenosas , Radioisótopos do Iodo , Masculino , Polietilenoglicóis/administração & dosagem , Ratos , Ratos Sprague-Dawley , Superóxido Dismutase/administração & dosagemRESUMO
Previous investigations have shown that brain prostaglandin levels are transiently elevated following experimental fluid percussion brain injury. Associated with these increased prostaglandin levels there is free radical production and abnormalities in cerebral arteriolar function. The purpose of this study was to determine whether experimental fluid percussion brain injury in cats is associated with increased systemic levels of prostaglandins and the lipoxygenase product, 12-HETE. Blood samples were collected before and at various periods of time after 2.7 atm of fluid percussion brain injury was produced in adult cats. Prostaglandin and 12-HETE analysis was performed by radioimmunoassay after extraction of the plasma samples. The control levels for 6-keto-PGF1 alpha, PGE2, and 12-HETE were 477 +/- 42, 2,372 +/- 431, and 13,328 +/- 1,769 pg/ml, respectively. Following injury all three eicosanoids reached peak plasma levels by 1-5 min after injury. The percentile increases for all eicosanoids were similar and increased from 70 to 110%. The increases were sustained at up to 30 min postinjury and by 1 h after injury were at control levels. As in previous studies, hypertension following injury was maximal by 1 min postinjury and blood pressure had returned to near normal levels by 5 min postinjury. These studies demonstrate prolonged systemic increases in eicosanoids following injury. Since free radical production and vascular damage occur concomitantly with eicosanoid production, the prolonged increases in these products suggest that there is an attainable therapeutic window following injury during which administration of free radical scavengers may decrease radical damage and reduce the consequences of injury.
Assuntos
6-Cetoprostaglandina F1 alfa/sangue , Concussão Encefálica/sangue , Dinoprostona/sangue , Ácidos Hidroxieicosatetraenoicos/sangue , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico , Animais , Gatos , Lipoxigenase/metabolismo , Prostaglandina-Endoperóxido Sintases/metabolismo , Valores de Referência , Fatores de TempoRESUMO
One of the goals of our laboratory is to examine how the presence of drugs of abuse will influence traumatic brain injury. Previous studies in our laboratory have shown that cocaine or lidocaine treatment before experimental fluid percussion brain injury in rats reduces the cortical hypoperfusion normally found in the early posttraumatic period. The purpose of the current study was to determine if pretreatment with cocaine or lidocaine is also associated with changes in trauma-induced suppression of reflexes and motor and cognitive dysfunction that occurs following traumatic brain injury (TBI). Twenty-four hours after surgical preparation, rats were randomly assigned to a saline or drug pretreatment group, cocaine (0.5, 2, or 5 mg/kg) or lidocaine (2 mg/kg), which was injected via the tail vein. None of the drug pretreatments worsened injury. Lidocaine and cocaine decreased the duration of suppression of some neurological reflexes and reduced posttraumatic body weight losses. Lidocaine and cocaine both decreased postinjury motor deficits. Lidocaine and cocaine did not affect cognitive function on days 11-15 postinjury. The mechanism by which lidocaine improves acute neurological and motor function following brain injury is unknown, but may involve improved posttraumatic cortical blood flow, as seen in our previous study. Our results, along with other studies showing lidocaine to be neuroprotective in animal models of ischemia, suggest that studies of the effect of posttraumatic administration of lidocaine are warranted.
Assuntos
Comportamento Animal/efeitos dos fármacos , Lesões Encefálicas/psicologia , Cocaína/farmacologia , Lidocaína/farmacologia , Ferimentos não Penetrantes/psicologia , Animais , Peso Corporal/efeitos dos fármacos , Lesões Encefálicas/patologia , Lesões Encefálicas/fisiopatologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Sistema Nervoso/fisiopatologia , Equilíbrio Postural/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Fatores de Tempo , Ferimentos não Penetrantes/patologia , Ferimentos não Penetrantes/fisiopatologiaRESUMO
The purpose of this study was to develop a simple, reproducible model for examining the morphologic, physiologic, and biochemical consequences of stretch-induced injury on tissue-cultured cells of brain origin. Rat cortical astrocytes from 1- to 2-day-old rats were cultured to confluency in commercially available 25-mm-diameter tissue culture wells with a 2-mm-thick flexible silastic bottom. A cell injury controller was used to produce a closed system and exert a rapid positive pressure of known amplitude (psi) and duration (msec). The deformation of the membrane, and thus the stretch of the cells growing on the membrane, was proportional to the amplitude and duration of the air pressure pulse. Extent of cell injury was qualitatively assessed by light and electron microscopy and quantitatively assessed by nuclear uptake of the fluorescent dye propidium iodide, which is excluded from cells with intact membranes. Lactate dehydrogenase (LDH) enzyme release was measured spectrophotometrically. Cell injury was found to be proportional to the extent of the silastic membrane deformation. Increasing cell stretch caused mitochondrial swelling and vacuolization as well as disruption of glial filaments. Stretching also caused increased dye uptake, with maximum dye uptake occurring with a 50 msec pressure pulse duration, whereas deformations produced over longer periods of time (seconds) caused little dye uptake. With increasing postinjury survival fewer cells took up dye, implying cell repair. LDH release was also proportional to the amplitude of cell stretch, with maximum release occurring within 2 h of injury. In summary we have developed a simple, reproducible model to produce graded, strain-related injuries in cultured cells. Our continuing experiments suggest that this model can be used to study the biochemistry and physiology of injury as well as serve as a tool to examine the efficacy of therapeutic agents.
Assuntos
Astrócitos/patologia , Lesões Encefálicas/patologia , Técnicas de Cultura de Células/métodos , Modelos Animais de Doenças , Pressão do Ar , Animais , Astrócitos/enzimologia , Astrócitos/ultraestrutura , Lesões Encefálicas/enzimologia , Lesões Encefálicas/metabolismo , Técnicas de Cultura de Células/instrumentação , Morte Celular/fisiologia , Membrana Celular/fisiologia , Núcleo Celular/metabolismo , Tamanho Celular/fisiologia , Sobrevivência Celular/fisiologia , Células Cultivadas/patologia , L-Lactato Desidrogenase/metabolismo , Dilatação Mitocondrial/fisiologia , Neuroglia/patologia , Propídio , Ratos , Ratos Endogâmicos , Resistência à TraçãoRESUMO
Previous studies in our laboratory have shown that polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) or lidocaine treatment before experimental fluid-percussion brain injury in rats reduces the cortical hypoperfusion normally found in the early posttraumatic period. The purpose of the current study was to determine if posttreatment with PEG-SOD or lidocaine is also associated with changes in the trauma-induced suppression of motor and cognitive function that occurs following traumatic brain injury (TBI). Twenty-four hours after surgical preparation, rats were randomly assigned to a saline or drug posttreatment group, PEG-SOD (pegorgotein, Dismutec 10,000 IU/kg) or lidocaine (2 mg/kg), which was injected iv 30 min after moderate injury. PEG-SOD completely prevented beam walk deficits on days 1-5 postinjury while lidocaine similarly prevented beam walk deficits on days 2 through 5 postinjury. Both drugs produced a statistically insignificant trend for a decrease in beam balance duration deficits on days 1-5 postinjury and had no effect on cognitive function, as assessed by the Morris water maze, on days 11 through 15 postinjury. The mechanism by which PEG-SOD and lidocaine reduce posttraumatic motor deficits may be related to their free radical scavenging effect or previously reported effects on posttraumatic cerebral blood flow. To our knowledge, this is the first report of the effectiveness of these two agents in laboratory animals when administered after traumatic injury.