The nootropic compound BMY-21502 improves spatial learning ability in brain injured rats

Combination Therapy for Multi-Target Manipulation of Secondary Brain Injury Mechanisms

Traumatic brain injury (TBI) is a major healthcare problem that affects millions of people worldwide. Despite advances in understanding and developing preventative and treatment strategies using preclinical animal models, clinical trials to date have failed, and a 'magic bullet' for effectively treating TBI-induced damage does not exist. Thus, novel pharmacological strategies to effectively manipulate the complex and heterogeneous pathophysiology of secondary injury mechanisms are needed. Given that goal, this paper discusses the relevance and advantages of combination therapies (COMTs) for 'multi-target manipulation' of the secondary injury cascade by administering multiple drugs to achieve an optimal therapeutic window of opportunity (e.g., temporally broad window) and compares these regimens to monotherapies that manipulate a single target with a single drug at a given time. Furthermore, we posit that integrated mechanistic multiscale models that combine primary injury biomechanics, secondary injury mechanobiology/neurobiology, physiology, pharmacology and mathematical programming techniques could account for vast differences in the biological space and time scales and help to accelerate drug development, to optimize pharmacological COMT protocols and to improve treatment outcomes.

Pathophysiology and Treatment of Memory Dysfunction After Traumatic Brain Injury

Memory is fundamental to everyday life, and cognitive impairments resulting from traumatic brain injury (TBI) have devastating effects on TBI survivors. A contributing component to memory impairments caused by TBI is alteration in the neural circuits associated with memory function. In this review, we aim to bring together experimental findings that characterize behavioral memory deficits and the underlying pathophysiology of memory-involved circuits after TBI. While there is little doubt that TBI causes memory and cognitive dysfunction, it is difficult to conclude which memory phase, i.e., encoding, maintenance, or retrieval, is specifically altered by TBI. This is most likely due to variation in behavioral protocols and experimental models. Additionally, we review a selection of experimental treatments that hold translational potential to mitigate memory dysfunction following injury.

Fluorine-Containing Diazines in Medicinal Chemistry and Agrochemistry

The combination of a fluorine atom and a diazine ring, which both possess unique structural and chemical features, can generate new relevant building blocks for the discovery of efficient fluorinated biologically active agents. Herein we give a comprehensive review on the biological activity and synthesis of fluorine containing, pyrimidine, pyrazine and pyridazine derivatives with relevance to medicinal and agrochemistry.

A review of pharmacological treatments used in experimental models of traumatic brain injury

PRIMARY OBJECTIVE

We provide a review of recent chronic and delayed rehabilitative pharmacological treatments examined in experimental models of traumatic brain injury. There is a specific emphasis on studies aiming to enhance cognitive recovery.

MAIN OUTCOMES AND RESULTS

Decreased neuronal activity is believed to contribute to persistent cognitive disabilities. Neurotransmitter based rehabilitative treatments that increase neuronal activity may assist in the recovery of cognitive function. However, timing and dosage of drug treatment are influential in cognitive enhancement. Drug treatments that affect single and multiple neurotransmitter systems have the ability to significantly influence recovery of function following brain injury.

CONCLUSIONS

Understanding the relationship between neural disturbances and functional deficits following brain injury is challenging. Cognitive impairment may be the result of a single event or multiple events that occur after the initial insult. Increasing neuronal activity during the chronic phase of injury seems to be an effective treatment strategy for facilitating cognitive recovery. Pharmacological agents do not necessarily display the same effects in an injured brain as in a non-injured brain. Thus, further research is needed to establish the effectiveness of rehabilitative drug treatments.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

Overexpression of Bcl-2 is neuroprotective after experimental brain injury in transgenic mice

The cell death regulatory protein, Bcl-2, has been suggested to participate in the pathophysiology of various neurological disorders, including traumatic brain injury (TBI). The cognitive function and histopathologic sequelae after controlled cortical impact brain injury were evaluated in transgenic (TG) mice that overexpress human Bcl-2 protein (n = 13) and their wild type (WT) controls (n = 9). Although brain-injured Bcl-2 TG mice exhibited similar posttraumatic deficits in a Morris water maze (MWM) test of spatial memory as their WT counterparts at 1 week postinjury, the preinjury learning ability of Bcl-2 TG mice was impaired significantly compared with their WT littermates (P < 0.05). In contrast, histopathologic analysis revealed significantly attenuated tissue loss in the ipsilateral hemisphere (p < 0.01) and decreased tissue loss in ipsilateral hippocampal area CA3 (P < 0.001) and the dentate gyrus (P < 0.01) in brain-injured Bcl-2 TG mice compared with brain-injured WT mice. Immunohistochemical evaluation of glial fibrillary acidic protein also revealed a significant decrease in reactive astrocytosis in the ipsilateral dorsal thalamus (P < 0.05) and the ventral thalamus (P < 0.01) in brain-injured Bcl-2 TG mice. These results suggest that overexpression of Bcl-2 protein may play a protective role in neuropathologic sequelae after TBI.

Effects of six weeks of chronic ethanol administration on the behavioral outcome of rats after lateral fluid percussion brain injury

This study examined the effects of 6 weeks of chronic ethanol administration on the behavioral outcome in rats after lateral fluid percussion (FP) brain injury. Rats were given either an ethanol liquid diet (ethanol diet-groups) or a pair-fed isocaloric sucrose control diet (control diet groups) for 6 weeks. After 6 weeks, the ethanol diet was discontinued for the ethanol diet rats and they were then given the control sucrose diet for 2 days. During those 2 days, the rats were trained to perform a beam-walking task and subjected to either lateral FP brain injury of low to moderate severity (1.8 atm) or to sham operation. In both the control diet and the ethanol diet groups, lateral FP brain injury caused beam-walking impairment on days 1 and 2 and spatial learning disability on days 7 and 8 after brain injury. There were no significant differences in beam-walking performance and spatial learning disability between brain injured animals from the control and ethanol diet groups. However, a trend towards greater behavioral deficits was observed in brain injured animals in the ethanol diet group. Histologic analysis of both diet groups after behavioral assessment revealed comparable ipsilateral cortical damage and observable CA3 neuronal loss in the ipsilateral hippocampus. These results only suggest that chronic ethanol administration, longer than six weeks of administration, may worsen behavioral outcome following lateral FP brain injury. For more significant behavioral and/or morphological change to occur, we would suggest that the duration of chronic ethanol administration must be increased.

Enduring cognitive, neurobehavioral and histopathological changes persist for up to one year following severe experimental brain injury in rats

Clinical studies have demonstrated that patients sustain prolonged behavioral deficits following traumatic brain injury, in some cases culminating in the cognitive and histopathological hallmarks of Alzheimer's disease. However, few studies have examined the long-term consequences of experimental traumatic brain injury. In the present study, anesthetized male Sprague-Dawley rats (n = 185) were subjected to severe lateral fluid-percussion brain injury (n = 115) or sham injury (n = 70) and evaluated up to one year post-injury for cognitive and neurological deficits and histopathological changes. Compared with sham-injured controls, brain-injured animals showed a spatial learning impairment that persisted up to one year post-injury. In addition, deficits in specific neurologic motor function tasks also persisted up to one year post-injury. Immunohistochemistry using multiple antibodies to the amyloid precursor protein and/or amyloid precursor protein-like proteins revealed novel axonal degeneration in the striatum, corpus callosum and injured cortex up to one year post-injury and in the thalamus up to six months post-injury. Histologic evaluation of injured brains demonstrated a progressive expansion of the cortical cavity, enlargement of the lateral ventricles, deformation of the hippocampus, and thalamic calcifications. Taken together, these findings indicate that experimental traumatic brain injury can cause long-term cognitive and neurologic motor dysfunction accompanied by continuing neurodegeneration.

Twofold overexpression of human beta-amyloid precursor proteins in transgenic mice does not affect the neuromotor, cognitive, or neurodegenerative sequelae following experimental brain injury

By using transgenic mice that overexpress human beta-amyloid precursor proteins (APPs) at levels twofold higher than endogenous APPs, following introduction of the human APP gene in a yeast artificial chromosome (YAC), we examined the effects of controlled cortical impact (CCI) brain injury on neuromotor/cognitive dysfunction and the development of Alzheimer's disease (AD)-like neuropathology. Neuropathological analyses included Nissl-staining and immunohistochemistry to detect APPs, beta-amyloid (Abeta), neurofilament proteins, and glial fibrillary acidic protein, whereas Abeta levels were measured in brain homogenates from mice subjected to CCI and control mice by using a sensitive sandwich enzyme-linked immunosorbent assay. Twenty APP-YAC transgenic mice and 17 wild type (WT) littermate controls were anesthetized and subjected to CCI (velocity, 5 m/second; deformation depth, 1 mm). Sham (anesthetized but uninjured) controls (n = 10 APP-YAC; n = 8 WT) also were studied. Motor function was evaluated by using rotarod, inclined-plane, and forelimb/hindlimb flexion tests. The Morris water maze was used to assess memory. Although CCI induced significant motor dysfunction and cognitive deficits, no differences were observed between brain-injured APP-YAC mice and WT mice at 24 hours and 1 week postinjury. By 1 week postinjury, both cortical and hippocampal CA3 neuron loss as well as extensive astrogliosis were observed in all injured animals, suggesting that overexpression of human APPs exhibited no neuroprotective effects. Although AD-like pathology (including amyloid plaques) was not observed in either sham or brain-inj ured animals, a significant decrease in brain concentrations of only Abeta terminating at amino acid 40 (Abeta x-40) was observed following brain injury in APP-YAC mice (P < 0.05 compared with sham control levels). Our data show that the APP-YAC mice do not develop AD-like neuropathology following traumatic brain injury. This may be because this injury does not induce elevated levels of the more amyloidogenic forms of human Abeta (i.e., Abeta x-42/43) in these mice.

Repeated acquisition of a spatial navigation task in mice: effects of spacing of trials and of unilateral middle cerebral artery occlusion

The working memory version of the Morris water escape task, the repeated acquisition task, consists of trial pairs in which an animal is started twice from the same start position. Animals have mastered this task when they need less time to find the platform in the second of the two trials. In this study, study, male C57BL mice were trained on this task with massed, spaced, or spaced delay trials in which there was a 90-min delay between the first and second trials of a pair. The mice trained with spaced trials learned the repeated acquisition task, whereas the mice trained with massed or spaced delay trials were not consistently able to do so. When the mice had reached a stable baseline performance, the middle cerebral artery (MCA) was occluded or the mice were sham-operated. Then, the effects of the MCA occlusion (MCA-O) on the performance in the repeated acquisition tasks were studied. MCA occlusion hardly affected the performance in this task, irrespective of the spacing condition of the trials, although surgery per se seemed to have a transient disruptive effect.

Effect of tetrahydroaminoacridine, a cholinesterase inhibitor, on cognitive performance following experimental brain injury

An emerging literature exists in support of deficits in cholinergic neurotransmission days to weeks following experimental traumatic brain injury (TBI). In addition, novel cholinomimetic therapeutics have been demonstrated to improve cognitive outcome following TBI in rats. We examined the effects of repeated postinjury administration of a cholinesterase inhibitor, tetrahydroaminoacridine (THA), on cognitive performance following experimental TBI. Rats were either injured at a moderate level of central fluid percussion TBI (2.1+/-0.1 atm) or were surgically prepared but not delivered a fluid pulse (sham injury). Beginning 24 h after TBI or sham injury, rats were injected (IP) daily for 15 days with an equal volume (1.0 ml/kg) of either 0.0, 1.0, 3.0, or 9.0 mg/kg THA (TBI: n = 8, 8, 10, and 7, respectively, and Sham: n = 5, 7, 8, 7, respectively). Cognitive performance was assessed on Days 11-15 after injury in a Morris water maze (MWM). Analysis of maze latencies over days indicated that chronic administration of THA produced a dose-related impairment in MWM performance in both the injured and sham groups, with the 9.0 mg/kg dose producing the largest deficit. The 1.0 and 3.0 mg/kg doses of THA impaired MWM performance without affecting swimming speeds. Thus, the results of this investigation do not support the use of THA as a cholinomimetic therapeutic for the treatment of cognitive deficits following TBI.

Insulin-like growth factor-1 (IGF-1) improves both neurological motor and cognitive outcome following experimental brain injury

We evaluated the efficacy of insulin-like growth factor-1 (IGF-1) in attenuating neurobehavioral deficits following lateral fluid percussion (FP) brain injury. Male Sprague-Dawley rats (345-425 g, n = 88) were anesthetized and subjected to FP brain injury of moderate severity (2.4-2.9 atm). In Study 1, IGF-1 (1.0 mg/kg, n = 9) or vehicle (n = 14) was administered by subcutaneous injection at 15 min postinjury and similarly at 12-h intervals for 14 days. In animals evaluated daily for 14 days, IGF-1 treatment attenuated motor dysfunction over the 2-week period (P < 0.02). In Study 2, IGF-1 (4 mg/kg/day, n = 8 uninjured, n = 13 injured) or vehicle (n = 8 uninjured, n = 13 injured) was administered for 2 weeks via a subcutaneous pump implanted 15 min postinjury. IGF-1 administration was associated with increased body weight and mild, transient hypoglycemia which was more pronounced in brain-injured animals. At 2 weeks postinjury (P < 0.05), but not at 48 h or 1 week, brain-injured animals receiving IGF-1 showed improved neuromotor function compared with those receiving vehicle. IGF-1 administration also enhanced learning ability (P < 0.03) and memory retention (P < 0.01) in brain-injured animals at 2 weeks postinjury. Taken together, these data suggest that chronic, posttraumatic administration of the trophic factor IGF-1 may be efficacious in ameliorating neurobehavioral dysfunction associated with traumatic brain injury.

Progressive atrophy and neuron death for one year following brain trauma in the rat

Although atrophic changes have been well described following traumatic brain injury (TBI) in humans, little is known concerning the mechanisms or progression of brain tissue loss. In the present study, we evaluated the temporal profile of histopathological changes following parasagittal fluid-percussion (FP) brain injury in rats over 1 year postinjury. Anesthetized 3-4 month-old Sprague-Dawley Rats (n = 51) were subjected to FP brain injury of high severity (2.5-2.9 atm, n = 51) or sham treatment (n = 27). At 1 h, 2 h, 48 h, 1 week, 2 weeks, 1 month, 2 months, 6 months and 1 year after brain injury or sham treatment, these animals were humanely euthanized. Brain sections were analyzed with image-processing techniques to determine the extent of cortical tissue loss and shrinkage of the hippocampal pyramidal cell layer. In addition, cell counting was performed to determine the number of neurons in the dentate hilus of the hippocampus, and glial fibrillary acidic protein (GFAP) immunostaining was used to reveal reactive astrocytosis. Examination of the injured brains revealed substantial and progressive tissue loss with concomitant ventriculomegaly in the hemisphere ipsilateral to injury. The regions with the most notable progressive atrophy included the cortex, hippocampus, thalamus, and septum. Quantitative analysis demonstrated a significantly progressive loss of cortical tissue as well as shrinkage of the hippocampal pyramidal cell layer ipsilateral to injury over 1 year following injury. In addition, reactive astrocytosis in regions of atrophy and progressive bilateral death of neurons in the dentate hilus was observed for 1 year following injury. These results suggest that a chronically progressive degenerative process may be initiated by brain trauma. Thus, there is a temporally broad window within which to introduce novel therapeutic strategies designed to ameliorate the short and long-term consequences of brain trauma.

Morris water maze deficits in rats following traumatic brain injury: lateral controlled cortical impact

This experiment utilized a laterally placed controlled cortical impact model of traumatic brain injury (TBI) to assess changes on spatial learning and memory in the Morris water maze (MWM). Adult rats were subjected to one of two different levels of cortical injury, mild (1 mm) or moderate (2 mm) deformation, and subsequently tested for their ability to learn (acquisition) or remember (retention) a spatial task, 7 or 14 days after injury. Results revealed an injury-dependent deficit for experimental animals compared to sham-operated controls. Not only did the TBI result in longer escape latencies, but also significant deficits in search time and relative target visits. Although the moderately injured animals demonstrated significant histopathology in the cortex and hippocampus, mildly injured subjects demonstrated no obvious tissue destruction, but did manifest significant behavioral change. These results demonstrate that a laterally placed controlled cortical impact is capable of producing significant cognitive deficits on both acquisition and retention paradigms utilizing the MWM.

Effects of VA-045 on learning and memory deficits in traumatic brain injury (TBI)-induced retrograde and anterograde amnesic mice

1. No specific regimen has been developed to treat post-traumatic amnesia in man. In the present study, we examined the effects of (+)-eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a novel derivative of apovincaminic acid, on learning and memory deficits associated with a mild traumatic brain injury (TBI) in mice. 2. Two kinds of amnesia, TBI-induced retrograde amnesia (TRA) and anterograde amnesia (TAA), were produced by means of post- and pre-acquisition head injury, respectively, by a simple weight-drop device. A novel procedure of water-finding task was used to assess learning and memory functions. 3. Both TRA and TAA mice were dramatically impaired in the task performance, with prolonged latencies for finding and drinking in either retention test or retest, indicating that retention was impaired in TRA mice while learning and retention were impaired in TAA mice. 4. VA-045 administered 30 min post-trauma in TRA mice dramatically shortened the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the retention deficit observed in TRA mice. 5. VA-045 administered 30 min post-trauma in TAA mice dramatically attenuated the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the learning and retention deficits observed in TAA mice. 6. Administration of VA-045 30 min pre-trauma in normal mice markedly attenuated the delay of latencies for finding and drinking after trauma in both retention test and retest, which shows that VA-045 significantly prevented learning and retention deficits after TBI. 7. Motor activities were not significantly affected by either the TBI or the chemical treatment at the time of task examination in either experimental model. 8. It is concluded that VA-045 may have potential effects on learning and memory deficits observed in either TBI-induced retrograde or anterograde amnesia.

Neuronal cell loss in the CA3 subfield of the hippocampus following cortical contusion utilizing the optical disector method for cell counting

Unilateral cortical contusion in the rat results in cell loss in both the cortex and hippocampus. Pharmacological intervention with growth factors or excitatory neurotransmitter antagonists may reduce cell loss and improve neurological outcome. The window of opportunity for such intervention remains unclear because a detailed temporal analysis of neuronal loss has not been performed in the rodent cortical contusion model. To elucidate the time course of hippocampal CA3 neuronal death ensuing cortical contusion, we employed the optical disector method for assessing the total number of CA3 neurons at 1 and 6 hours, 1, 2, 10, and 30 days following injury. This stereological technique allows reporting of total cell numbers within a given region and is unaffected by change in the volume of the structure or cell size. A rapid and significant reduction in neurons/mm3 in the ipsilateral CA3 field was observed by 1 h following trauma. However, a significant increase in neurons/mm3 was seen at 30 days postinjury. This surprising finding is a result of CA3 volume shrinkage and redistribution of CA3 neurons. Utilization of the optical disector reveals that regardless of an increase in neurons/mm3 at 30 days following injury, CA3 cell loss reaches 41% of control animals by 1 day posttrauma and remains near that level at all subsequent time points examined. It is estimated that there are about 156,000 neurons in the CA3 region in control animals. By 1 h following cortical contusion the cell population decreases to 93,000 neurons indicating a very rapid cell loss. This suggests a window of less than 24 h for pharmacological intervention in order to save CA3 neurons following cortical contusion.

Effects of the novel NMDA antagonists CP-98,113, CP-101,581 and CP-101,606 on cognitive function and regional cerebral edema following experimental brain injury in the rat

The present study evaluated the effects of two novel N-methyl-D-aspartate (NMDA) receptor blockers and ifenprodil derivatives, CP-101,606 and CP-101,581, and their racemic mixture CP-98,113, on spatial memory and regional cerebral edema following experimental fluid-percussion (FP) brain injury in the rat (n = 66). Fifteen minutes after brain injury (2.5 atm), animals received either (1) CP-98,113 (5 mg/kg, i.p., n = 11), (2) CP-101,581 (5 mg/kg, i.p., n = 13), (3) CP-101,606 (6.5 mg/kg, i.p., n = 12), or (4) DMSO vehicle (equal volume, n = 12); followed by a continuous 24-h subcutaneous infusion of drug at a rate of 1.5 mg/kg/h by means of miniature osmotic (Alzet) pumps implanted subcutaneously. Control (uninjured) animals were subjected to identical anesthesia and surgery without injury and received DMSO vehicle (n = 8); CP-98,113 (5 mg/kg, i.p., n = 3); CP-101,581 (5 mg/kg, i.p., n = 3); or CP-101,606 (6.5 mg/kg, i.p., n = 3). FP brain injury produced a significant cognitive impairment assessed at 2 days postinjury using a well-characterized testing paradigm of visuospatial memory in the Morris Water Maze (MWM) (p < 0.001). Administration of either CP-98,113, CP-101,581, or CP-101,606 had no effect on sham (uninjured) animals, but significant attenuated spatial memory impairment assessed at 2 days postinjury (p = 0.004, p = 0.02, or p = 0.02, respectively). Administration of CP-89,113 but not CP-101,581 or CP-101,606 significantly reduced the extent of regional cerebral edema in the cortex adjacent to the site of injury (p < 0.05) and in the ipsilateral hippocampus (p < 0.05) and thalamus (p < 0.05). These results suggest that excitatory neurotransmission may play a pivotal role in the pathogenesis of memory dysfunction following traumatic brain injury (TBI) and that blockade of the NMDA receptor may significantly attenuate cognitive deficits associated with TBI.

Improvement of cognitive deficits and decreased cholinergic neuronal cell loss and apoptotic cell death following neurotrophin infusion after experimental traumatic brain injury

This study explores the effects of infusion of nerve growth factor (NGF) on behavioral outcome and cell death in the septal region using the clinically relevant model of fluid-percussion brain injury in the rat. Animals were subjected to fluid-percussion brain injury and 24 hours later a miniosmotic pump was implanted to infuse NGF (12 animals) or vehicle (12 animals) directly into the region of maximum injury for 2 weeks. Four weeks postinjury the animals were tested for cognitive function using a Morris Water Maze paradigm. Neurological motor function was evaluated over a 4-week postinjury period. The rats receiving NGF infusions had significantly higher memory scores than vehicle-treated animals. Examination of the cholinergic neurons in the medial septal region using choline acetyltransferase immunohistochemistry demonstrated significant cell loss after injury. Infusion of NGF significantly attenuated loss of these cholinergic neurons. A second group of animals was subjected to fluid-percussion brain injury alone (23 rats) or injury followed by NGF infusion (18 rats). These animals were killed between 24 hours and 2 weeks postinjury and the septal region was examined for the presence of apoptotic cells using the terminal deoxynucleotidyl transferase-mediated biotinylated-deoxyuridinetriphosphate nick-end labeling technique. Apoptotic cells were identified as early as 24 hours postinjury; their numbers peaked at 4 and 7 days, and then declined by 14 days. The NGF-treated animals had some apoptotic cells; however, even at 7 days there were significantly fewer of these cells. No significant motor differences were observed between the NGF- and vehicle-treated groups. These data indicate that NGF administration beginning 24 hours after fluid-percussion brain injury has a beneficial effect on cognition and results in sparing of cholinergic septal neurons. These improvements persist after cessation of NGF administration. The beneficial effects of NGF may be related to its ability to attenuate traumatically induced apoptotic cell death.

(+)-Eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a putative cognitive enhancer, facilitates recovery from concussive brain injury-induced learning and memory impairments in mice

We characterized alterations in the ability of concussive brain injury (CBI) models to perform a water-finding task and examined effects of (+)-eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a novel apovincaminic acid derivative, on post-traumatic impairments in latent learning and memory processes. Two types of CBI-induced amnesia (retrograde and anterograde) were produced by means of post- or preacquisition head impact using a simple weight-drop device. Profound impairments of latent learning and memory processes related to retention and retrieval were observed in the CBI mice. In the CBI-induced retrograde amnesia model, VA-045 (0.5-4.0 mg/kg) significantly ameliorated impairments of latent learning and retention in both the retention test and the retest. In the CBI-induced anterograde amnesia model, the protective effects of the compound on impairments in latent learning and retention or retrieval were significant in both the retention test and the retest. These results suggested that VA-045 may be a novel cognitive enhancer for attenuating or protecting against the learning and memory dysfunction associated with CBI.

Hippocampal degeneration inducing impairment of learning in rats: model of dementia?

In the pharmacological field, the development of drugs effective for dementia is now widely anticipated because of the increase in the elderly population. Dementia has some histological degeneration in the brain, including the hippocampus. Preclinical evaluations of such drugs use animal models with memory impairment, since memory impairment is a major criterion of dementia. We therefore investigated two animal models with hippocampal degeneration. Neonatal administration of monosodium glutamate (MSG) induced specific degeneration of hippocampal pyramidal cells in the CA1 region of Wistar rats in adulthood. In these animals, the correct response rate during the acquisition period of light-dark discrimination learning was significantly lower than that in the control group. No significant changes were noted in the hippocampal concentrations of neurotransmitter substances, including acetylcholine and glutamate. In the second model, similar histological changes were observed at 3 weeks after oral administration of trimethyltin (TMT). These histological changes were accompanied by a reduction in the intrahippocampal concentrations of acetylcholine and glutamate. In the case of light-dark discrimination learning, neither pre- nor post-training administration of TMT affected the correct response rate during both the acquisition and retention test periods. In the case of 8-arm radial maze learning, the increase in correct response rate was significantly suppressed in comparison with that of the control group when TMT was administered at 4 weeks before starting the acquisition trial. This suppression was followed by a lower response rate in the retention test. On the other hand, the correct response rates in retention tests were not affected when TMT was administered after completion of the acquisition trial. These findings indicate that sole degeneration of the hippocampus was able to induce different types of memory impairment, and single evaluation of a drug with one learning paradigm was difficult to justify that a drug is effective for dementia.

Indeloxazine hydrochloride improves impairment of passive avoidance performance after fluid percussion brain injury in rats

We studied behavioral and histological changes after fluid percussion brain injury and the effects of indeloxazine hydrochloride, a cerebral activator, on these post-traumatic changes in rats. An acquisition trial in passive avoidance task was conducted on the 3rd day after injury. The latency of step-through in injured rats was significantly (p < 0.05) shorter than that in sham-operated rats on the 4th, 10th and 14th days after the operation. There were injury-induced neurological deficits on days 1-4 post-injury. Histological changes were observed in the peripheral area of the cortical lesion at the impact site and in the thalamus but not in the hippocampus on the 14th day. Indeloxazine (10 and 20 mg/kg, p.o.) administered once a day from the 3rd (30 min prior to the acquisition trial) to the 9th day after injury significantly (p < 0.05) improved the impairment of the passive avoidance performance without affecting locomotor activity. Indeloxazine showed no significant effects on either neurological deficits or the cortical lesion area. These results suggest that impairment of passive avoidance performance occurs without apparent histological damage in the hippocampus after fluid percussion brain injury and is attenuated by post-traumatic treatment with indeloxazine.

Exposure to environmental complexity promotes recovery of cognitive function after traumatic brain injury

This study was designed to determine whether exposure to a complex environment after traumatic brain injury (TBI) would promote the recovery of cognitive function. Rats were injured at a moderate level of fluid percussion injury (2.1 atm) or were prepared for injury but were not injured (sham injury). Immediately after the injury or sham injury, the injured/complex (n = 8) and the sham/complex (n = 7) groups were placed into a complex environment. The complex environment was a 89 x 89-cm enclosure with different types of bedding and objects that provided motor, olfactory, tactile, and visual stimulation. The injured/standard (n = 8) and the sham/standard (n = 8) groups were returned to the animal vivarium where they were housed individually in standard wire mesh cages (24 x 20 x 18 cm). On days 11-15 (postinjury), performance in the Morris water maze was assessed. Analysis of the latency to reach the goal platform indicated that injured animals recuperating in the complex environment performed significantly better than injured animals recovering in the standard environment (p < 0.01). In fact, injured animals in the complex environment performed as well as both sham-injured groups. The improved performance of injured rats recovering in the enriched environment occurred in the absence of environmentally induced alterations in brain weight. These results indicate that exposure to environmental complexity enhances recovery of cognitive function after TBI.

Chronic postinjury administration of MDL 26,479 (Suritozole), a negative modulator at the GABAA receptor, and cognitive impairment in rats following traumatic brain injury

The present experiment examined the efficacy of postinjury administration of MDL 26,479 (Suritozole), a negative modulator at the gamma-aminobutyric acidA (GABAA) receptor that enhances cholinergic function, in attenuating spatial memory deficits after traumatic brain injury in the rat. Two experiments were performed. In the delayed-dosing experiment, rats received a moderate level (2.1 atm) of fluid-percussion brain injury and were tested in the Morris water maze 11 to 15 days following injury. These rats were injected with either 5 mg/kg (eight rats) or 10 mg/kg (eight rats) of MDL 26,479 60 minutes before each water maze test. Additional rats were injured and treated with saline (eight rats) or were surgically prepared but not injured (eight rats). In the second experiment, an early postinjury dosing procedure was followed. Rats were injured in the same manner but drug treatment began 24 hours after injury and continued daily through Day 15. Results indicated that the rats in the delayed chronic dosing regimen did not differ from the injured, saline-treated rats in their latency to reach the goal platform (p > 0.05). However, those treated chronically beginning 24 hours after injury had significantly shorter latencies than the injured, saline-treated rats (p < 0.05). These results suggest that administration of agents that enhance cholinergic function may be an appropriate strategy for promoting cognitive recovery when given after traumatic brain injury. Furthermore, prolonged treatment may be necessary to elicit beneficial effects.

Post-injury administration of BIBN 99, a selective muscarinic M2 receptor antagonist, improves cognitive performance following traumatic brain injury in rats

Mild to moderate traumatic brain injury (TBI) is associated with enduring impairments of cognitive function in both humans and animals. However, few experiments have investigated the role of post-injury pharmacologic strategies for attenuating the observed cognitive impairment after TBI. This investigation examined the effects of selective blockade of the presynaptic muscarinic M2 autoreceptor with BIBN 99 on cognitive recovery following rodent TBI. Experiment 1 investigated the effects of delayed post-injury administration of BIBN 99 on cognitive performance following moderate central fluid percussion TBI (2.1 +/- 0.05 atm). On days 11-15 after injury-cognitive performance was assessed with a Morris water maze (MWM) task. One hour before MWM testing injured rats were injected (s.c.) with either vehicle (n = 9), 0.5 (n = 8), or 1.0 (n = 8) mg/kg of BIBN 99. Results indicated that injured rats receiving the delayed post-injury treatment with BIBN 99 performed no better than injured-vehicle treated rats. In experiment 2, injured rats were injected (s.c.) once daily with either vehicle (n = 9), 0.5 (n = 9), or 1.0 (n = 9) mg/kg of BIBN 99 throughout the duration of the experiment beginning 24 h after TBI. Sham-injured animals injected (s.c.) with vehicle (n = 9) or 1.0 (n = 8) mg/kg of BIBN 99 were included for comparison. On days 11-15 after injury, cognitive performance was assessed with the MWM procedure. Results of the second experiment indicated that both doses of BIBN 99 were effective in attenuating cognitive deficits in the MWM as compared to the injured-vehicle treated animals (P < 0.05 for both comparisons).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term effect of HU-211, a novel non-competitive NMDA antagonist, on motor and memory functions after closed head injury in the rat

HU-211 is a synthetic, non-psychotropic cannabinoid which acts as a non-competitive NMDA antagonist and antioxidant. We studied the drug's therapeutic window as well as its long-term effect on cognitive and motor functions in a model of closed head injury (CHI) in the rat. A weight-drop device was used to induce CHI in either anesthetized male rats. HU-211 (5 mg/kg) was administered i.v. to the experimental groups. For the therapeutic window study, drug was injected at 4 or 6 h after CHI. Edema (water content) and clinical status (neurological severity score, NSS) were evaluated at 24 h. Reduction of edema was slight, whereas improvement of NSS was significant when the drug was administered at 4 or 6 h (P = 0.0023 and 0.059, respectively). To determine the drug's long-term effect, it was administered 1 h after CHI and additional doses were later given. NSS was evaluated for a period of 30 d. A single dose of HU-211 given 1 h post-CHI improved the clinical outcome during the 30 d period (P < 0.01). Repetitive doses of HU-211 injected during the post traumatic period had similar effects. Cognitive functions were evaluated in the Morris water maze, with rats trained either before or after CHI. CHI resulted in a highly significant impairment of these abilities, whereas HU-211 treatment 1 h after CHI improved performance. Our results indicate that HU-211 is a potent cerebroprotective agent, with a therapeutic window of about 4 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased anticholinergic sensitivity following closed skull impact and controlled cortical impact traumatic brain injury in the rat

Evidence suggests that prolonged memory deficits in several neurodegenerative diseases are attributable to deficits in central cholinergic neurotransmission. In traumatic brain injury (TBI), such cholinergic deficits also may contribute to prolonged memory disturbances. This study determined whether moderate magnitudes of TBI produced by controlled cortical impact and mild magnitudes of experimental TBI produced by a new closed head impact technique in rats would produce an enhanced vulnerability to the memory disruptive effects of scopolamine, a muscarinic cholinergic receptor antagonist. Water maze performance was used to determine changes in cholinergic hippocampal function following TBI. In the first experiment, rats received a moderate level of TBI by means of a controlled cortical impact. A Morris water maze task assessed spatial memory function on days 30-34 postinjury. During the 5 day assessment period, statistical analyses showed a group main effect for swim latency. Subsequent post hoc analyses indicated that injured rats had significantly longer latencies on days 30 and 31 (p < 0.05, injury vs sham controls). By days 32-35, injured rats showed no statistically significant deficits in spatial memory performance. On day 35, scopolamine (1 mg/kg, IP) was injected into injured rats and sham-injured rats 15 min prior to being retested in the maze. Results showed that although the scopolamine had no effects on the performance of the sham-injured rats, the same dose significantly (p < 0.05) increased the latency to find the hidden platform in the injured group. In the second experiment, rats received a mild concussive closed head impact. Water maze performance was assessed on days 8-12 postinjury. No significant water maze performance deficits were observed. On day 13, injured and uninjured rats were pharmacologically challenged with scopolamine (1 mg/kg) and retested. Similar to the first experiment, injured rats manifested a significantly greater (p < 0.05) sensitivity to scopolamine than sham controls. The results from both experiments suggest that concussive and more severe levels of TBI can produce an enhanced vulnerability to disruption of cholinergically mediated memory function, even when memory function appears normal in the absence of secondary challenges. These data demonstrate that covert deficits can persist after the recovery of normal function. These deficits may be attributable to a decrease in the ability of cholinergic neurons to function properly. These data also provide important insights into features of receptor-coupled disturbances that could contribute to the maintenance of enduring cognitive deficits following TBI.