Anticonvulsive effects of the dopamine agonist lisuride maleate after experimental traumatic brain injury.
ABSTRACT Traumatic brain injury is a heterogeneous disease, encompassing a wide range of pathologies. The dopamine agonist lisuride is well established in the therapy of Parkinson's disease. Additionally to its dopaminergic effects it decreases prolactine release, reducing the amount of inflammatory mediators such as TNF-alpha or Il-6. Lisuride has strong binding affinity to serotonergic and histaminergic receptors on neuronal and glial cells leading to scavenging of highly reactive free radicals. Due to its interaction with dopaminergic D2 and D4 receptors as well as 5-HT-1A receptors, NMDA-receptor signaling and glutamate-mediated excitotoxicity can be modulated beneficially. Despite of these promising neuroprotective effects, experimental data scrutinizing the effects of lisuride after acute brain injury are sparse. We therefore investigated the effect of lisuride after controlled cortical impact injury (CCII) in rats. 70 male Sprague-Dawley rats were randomized to lisuride or to placebo treatment by an initial s.c. loading dose (0.3mg/kg BW) and following continuous application (0.5mg/kg/d) by s.c. implanted osmotic pumps. In three experimental groups we determined (sub)acute neuro-physiological changes after trauma. Mean arterial blood pressure, intracranial pressure, and electrical brain activity were monitored acutely for up to 3h after trauma. Brain edema formation was assessed 24h after CCII. Furthermore, contusion volumes were quantified by magnetic resonance tomography and neurological testing was performed for up to 7 days after injury. Associated with the administration of lisuride there was a significant reduction in duration and number of post-traumatic seizures. Despite of a sustained arterial hypotension following the initial bolus administration in the treatment group, contusion volumes and neurological function tests did not differ significantly in comparison to the control group. Overall, lisuride seems to have significant anticonvulsive effects but seems not to influence secondary brain damage in this experimental model.
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ABSTRACT: Clinical and experimental studies implicate most neuromodulatory systems in epileptogenesis. The dopaminergic system has a seizure-modulating effect that crucially depends on the different subtypes of dopamine (DA) receptors involved and the brain regions in which they are activated. Specifically, DA plays a major role in the control of seizures arising in the limbic system. Studies performed in a wide variety of animal models contributed to illustrate the opposite actions of D1-like and D2-like receptor signaling in limbic epileptogenesis. Indeed, signaling from D1-like receptors is generally pro-epileptogenic, whereas D2-like receptor signaling exerts an anti-epileptogenic effect. However, this view might appear quite simplistic as the complex neuromodulatory action of DA in the control of epileptogenesis likely requires a physiological balance in the activation of circuits modulated by these two major DA receptor subtypes, which determines the response to seizure-promoting stimuli. Here we will review recent evidences on the identification of molecules activated by DA transduction pathways in the generation and spread of seizures in the limbic system. We will discuss the intracellular signaling pathways triggered by activation of different DA receptors in relation to their role in limbic epileptogenesis, which lead to the activation of neuronal death/survival cascades. A deep understanding of the signaling pathways involved in epileptogenesis is crucial for the identification of novel targets for the treatment of epilepsy.Frontiers in Cellular Neuroscience 01/2013; 7:157. · 4.18 Impact Factor
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ABSTRACT: The similarities and differences of acute nonconvulsive seizures (NCS) and other epileptic events, e.g. periodic epileptiform discharges (PED) and intermittent rhythmic delta activities (IRDA), were characterized in rat models of penetrating and ischemic brain injuries. The NCS were spontaneously induced by either unilateral frontal penetrating ballistic-like brain injury (PBBI) or permanent middle cerebral artery occlusion (pMCAO) and detected by continuous EEG monitoring begun immediately after the injury and continued for 72 h or 24 h, respectively. Analysis of NCS profiles (incidence, frequency, duration, and time distribution) revealed a high NCS incidence in both injury models. The EEG waveform expressions of NCS and PED exhibited intrinsic variations which resembled human electrographic manifestations of post-traumatic and post-ischemic ictal and inter-ictal events, but these waveform variations were not distinguishable between two types of brain injury. However, the NCS after pMCAO occurred more acutely and intensely (latency=0.6 h, frequency = 25 episodes/rat) compared to the PBBI-induced NCS (latency=26 h, frequency = 10 episodes/rat), such that the most salient features differentiating post-traumatic and post-ischemic NCS were the intensity and time distribution of the NCS profiles. After pMCAO, nearly 50% of the seizures occurred within the first 2 h of injury, whereas after PBBI, NCS occurred sporadically (0-5% per hour) throughout the 72 h recording period. The PED were episodically associated with NCS. By contrast, the IRDA appeared to be independent of other epileptic events. This study provided comprehensive comparisons of post-traumatic and post-ischemic epileptic profiles. The identification of the similarities and differences across a broad spectrum of epileptic events may lead to differential strategies for post-traumatic and post-stroke seizure interventions.Journal of neurotrauma 12/2012; · 4.25 Impact Factor
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ABSTRACT: Analgesics and sedatives are frequently used in the treatment of acute brain injury and subsequent brain swelling. Most agents act on specific receptors to modulate neuronal activity, which is normally involved in feedback loops that direct system building and maintenance. We investigated the neurodegenerative effects of midazolam and isoflurane in a rat model of controlled cortical impact injury (CCII). Two hours prior to CCII, four experimental groups were treated with different agents including a minimum alveolar concentration (MAC 1.0) of isoflurane. For additional sedation, isoflurane MAC 1.67, midazolam alone, or midazolam in combination with flumazenil was used. Blood pressure and blood gas analysis were monitored to investigate systemic side effects. Two days after treatment, relative apoptotic cell counts were determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. With isoflurane and midazolam, electroencephalographic (EEG) recordings revealed a decrease in amplitude size and altered frequency distribution. Treatment using deep sedation with isoflurane MAC 1.67 or midazolam increased relative apoptotic cell count by 14.8% (95% CI 3.6 to 26.1, p<0.01) and 18.0% (95% CI 6.8 to 29.3, p<0.01), respectively. Co-treatment with flumazenil reversed the neurodegenerative effect of midazolam by -13.2% (95% CI -24.5 to -2.0, p<0.05). Functional neurological outcome was worse after isoflurane MAC 1.67 (18.8 score points; p<0.01) and midazolam (21.4 score points, p<0.001). Flumazenil antagonized the neurodegenerative effects of midazolam. In conclusion, neuronal survival and functional recovery are reduced by sedative use in a rat model of acute brain injury.Brain research 03/2013; · 2.83 Impact Factor