Extended thromboprophylaxis following colorectal surgery in patients with inflammatory bowel disease: a comprehensive systematic clinical review

AIM

Patients with inflammatory bowel disease (IBD) are at increased risk of postoperative venous thromboembolism (VTE) following major abdominal surgery. The pathogenesis is multifactorial and not fully understood. A combination of pathophysiology, patient and surgical risk factors increase the risk of postoperative VTE in these patients. Despite being at increased risk, IBD patients are not regularly prescribed extended pharmacological thromboprophylaxis following colorectal surgery. Currently, there is a paucity of evidence-based guidelines. Thus, the aim of this review is to evaluate the role of extended pharmacological thromboprophylaxis in IBD patients undergoing colorectal surgery.

METHOD

A search of Ovid Medline, EMBASE and PubMed databases was performed. A qualitative analysis was performed using 10 clinical questions developed by colorectal surgeons and a thrombosis haematologist. The Newcastle-Ottawa Scale was utilized to assess the quality of evidence.

RESULTS

A total of 1229 studies were identified, 38 of which met the final inclusion criteria (37 retrospective, one case-control). Rates of postoperative VTE ranged between 0.6% and 8.9%. Patient-specific risk factors for postoperative VTE included ulcerative colitis, increased age and obesity. Surgery-specific risk factors for postoperative VTE included open surgery, emergent surgery and ileostomy creation. Patients with IBD were more frequently at increased risk in the included studies for postoperative VTE than patients with colorectal cancer. The risk of bias assessment demonstrated low risk of bias in patient selection and comparability, with variable risk of bias in reported outcomes.

CONCLUSION

There is a lack of evidence regarding the use of extended pharmacological thromboprophylaxis in patients with IBD following colorectal surgery. As these patients are at heightened risk of postoperative VTE, future study and consideration of the use of extended pharmacological thromboprophylaxis is warranted.

Attenuation of acute mitochondrial dysfunction after traumatic brain injury in mice by NIM811, a non-immunosuppressive cyclosporin A analog

Following traumatic brain injury (TBI), mitochondrial function becomes compromised. Mitochondrial dysfunction is characterized by intra-mitochondrial Ca(2+) accumulation, induction of oxidative damage, and mitochondrial permeability transition (mPT). Experimental studies show that cyclosporin A (CsA) inhibits mPT. However, CsA also inhibits calcineurin. In the present study, we conducted a dose-response analysis of NIM811, a non-calcineurin inhibitory CsA analog, on mitochondrial dysfunction following TBI in mice, and compared the effects of the optimal dose of NIM811 (10 mg/kg i.p.) against an optimized dose of CsA (20 mg/kg i.p.). Male CF-1 mice were subjected to severe TBI utilizing the controlled cortical impact model. Mitochondrial respiration was assessed from animals treated with either NIM811, CsA, or vehicle 15 min post-injury. The respiratory control ratio (RCR) of mitochondria from vehicle-treated animals was significantly (p<0.01) lower at 3 or 12 h post-TBI, relative to shams. Treatment of animals with either NIM811 or CsA significantly (p<0.03) attenuated this reduction. Consistent with this finding, both NIM811 and CsA significantly reduced lipid peroxidative and protein nitrative damage to mitochondria at 12 h post-TBI. These results showing the ability of NIM811 to fully duplicate the mitochondrial protective efficacy of CsA supports the conclusion that inhibition of the mPT may be sufficient to explain CsA's protective effects.

Mitochondrial permeability transition in CNS trauma: Cause or effect of neuronal cell death?

Experimental traumatic brain injury (TBI) and spinal cord injury (SCI) result in a rapid and significant necrosis of neuronal tissue at the site of injury. In the ensuing hours and days, secondary injury exacerbates the primary damage, resulting in significant neurologic dysfunction. It is believed that alterations in excitatory amino acids (EAA), increased reactive oxygen species (ROS), and the disruption of Ca(2+) homeostasis are major factors contributing to the ensuing neuropathology. Mitochondria serve as the powerhouse of the cell by maintaining ratios of ATP:ADP that thermodynamically favor the hydrolysis of ATP to ADP + P(i), yet a byproduct of this process is the generation of ROS. Proton-pumping by components of the electron transport system (ETS) generates a membrane potential (DeltaPsi) that can then be used to phosphorylate ADP or sequester Ca(2+) out of the cytosol into the mitochondrial matrix. This allows mitochondria to act as cellular Ca(2+) sinks and to be in phase with changes in cytosolic Ca(2+) levels. Under extreme loads of Ca(2+), however, opening of the mitochondrial permeability transition pore (mPTP) results in the extrusion of mitochondrial Ca(2+) and other high- and low-molecular weight components. This catastrophic event discharges DeltaPsi and uncouples the ETS from ATP production. Cyclosporin A (CsA), a potent immunosuppressive drug, inhibits mitochondrial permeability transition (mPT) by binding to matrix cyclophilin D and blocking its binding to the adenine nucleotide translocator. Peripherally administered CsA attenuates mitochondrial dysfunction and neuronal damage in an experimental rodent model of TBI, in a dose-dependent manner. The underlying mechanism of neuroprotection afforded by CsA is most likely via interaction with the mPTP because the immunosuppressant FK506, which has no effect on the mPT, was not neuroprotective. When CsA was administrated after experimental SCI at the same dosage and regimen used TBI paradigms, however, it had no beneficial neuroprotective effects. This review takes a comprehensive and critical look at the evidence supporting the role for mPT in central nervous system (CNS) trauma and highlights the differential responses of CNS mitochondria to mPT induction and the implications this has for therapeutically targeting the mPT in TBI and SCI.

Overexpression of GDNF induces and maintains hyperinnervation of muscle fibers and multiple end-plate formation

This study examined the role of glial cell line-derived neurotrophic factor (GDNF) in synaptic plasticity at the developing neuromuscular junction. Transgenic mice overexpressing GDNF in skeletal muscle under the myosin light chain-1 promoter were isolated. Northern blot and ELISA at 6 weeks of age indicated that GDNF mRNA and protein levels were elevated threefold in the lateral gastrocnemius muscle (LGM) of the GDNF-transgenic animals. Histochemical examination of LGM tissue sections at 6 weeks of age revealed a 70% increase in the number of cholinesterase-positive end plates without changes in end-plate area. Multiple end plates on a single muscle fiber were also observed, in addition to multiple axonal processes terminating on individual end plates. No change in the number of spinal motoneurons, overall LGM size, or muscle type composition was observed. Finally, overexpression of GDNF in muscle caused hypertrophy of neuronal somata in dorsal root ganglia without affecting their number. These findings demonstrate that overexpression of a single neurotrophic factor in skeletal muscle induces multiple end-plate formation and maintains hyperinnervation well beyond the normal developmental period. We suggest that GDNF, a muscle-derived motoneuron neurotrophic factor, serves an important role in the regulation of synaptic plasticity in the developing and adult neuromuscular junction.

Caspase-3 apoptotic signaling following injury to the central nervous system

Apoptotic cell death is a fundamental and highly regulated biological process in which a cell is instructed to participate actively in its own demise. This process of cellular suicide is activated by developmental and environmental cues and normally plays an essential role in eliminating superfluous, damaged, and senescent cells of many tissue types. In recent years, a number of experimental studies have provided evidence of widespread neuronal and glial apoptosis following injury to the central nervous system (CNS). These studies indicate that injury-induced apoptosis can be detected from hours to days following injury and may contribute to neurological dysfunction. Given these findings, understanding the biochemical signaling events controlling apoptosis is a first step towards developing therapeutic agents which would target this cell death process. This review will focus on the molecular cell death pathways responsible for generating the apoptotic phenotype, summarize what is currently known about apoptotic signals activated in the injured CNS, and what potential strategies might be pursued to reduce this cell death process as a means to promote functional recovery.

Calcineurin-mediated BAD dephosphorylation activates the caspase-3 apoptotic cascade in traumatic spinal cord injury

We report here that activation of the caspase-3 apoptotic cascade in spinal cord injury is regulated, in part, by calcineurin-mediated BAD dephosphorylation. BAD, a proapoptotic member of the bcl-2 gene family, is rapidly dephosphorylated after injury, dissociates from 14-3-3 in the cytosol, and translocates to the mitochondria of neurons where it binds to Bcl-x(L). Pretreatment of animals with FK506, a potent inhibitor of calcineurin activity, or MK801, an NMDA glutamate receptor antagonist, blocked BAD dephosphorylation and abolished activation of the caspase-3 apoptotic cascade. These findings extend previous in vitro observations and are the first to implicate the involvement of glutamate-mediated calcineurin activation and BAD dephosphorylation as upstream, premitochondrial signaling events leading to caspase-3 activation in traumatic spinal cord injury.

Riluzole and methylprednisolone combined treatment improves functional recovery in traumatic spinal cord injury

The potential use of riluzole (a glutamate release inhibitor) alone or in combination with methyl-prednisolone (MP) in treating acute spinal cored injury (SCI) was examined. Rats received a contusion injury to the spinal cord using the NYU impactor and were treated with vehicle, riluzole (8 mg/kg), MP(30 mg/kg), or riluzole + MP at 2 and 4 h following injury. Animals continued to receive riluzole treatment (8 mg/kg) for a period of 1 week. The animals were then tested weekly for functional recovery using the BBB open field locomotor score. At the end of testing (6 weeks after injury), each spinal cord was examined for the amount of remaining tissue at the injury site and a myelination index was used to quantify remaining axons in the ventromedial white matter. In this study, only the combination treatment was found to significantly improve behavioral recovery as assessed using the BBB open field locomotor scale. In addition, the combination treatment promoted tissue sparing at the lesion epicenter, but had no clear effect on the index of myelination. The results of this study clearly demonstrate the potential beneficial effects of a combination approach in the treatment of traumatic SCI.

Riluzole increases high-affinity glutamate uptake in rat spinal cord synaptosomes

The purpose of this study was to examine the effect of the anti-convulsant agent, riluzole, on high-affinity glutamate uptake as measured in rat spinal cord synaptosomes. The rate of glutamate uptake was significantly increased in the presence of 0.1 microM and 1.0 microM riluzole, but not at the higher concentrations examined. Kinetics analysis demonstrated that riluzole (0.1 microM) decreased the apparent K(m) by 21% and increased the V(max) by 31%. Glutamate uptake also was significantly increased in spinal cord synaptosomes obtained from rats treated with 8 mg/kg (i.p.) of riluzole and sacrificed 4 h later. The increase in glutamate uptake in vitro was not affected by pretreatment either with H7, an inhibitor of PKA and PKC, or with the PKC activating phorbol ester, 12-O-tetradecanoylphorbol 13-acetate. Previous studies have shown that some of the actions of riluzole are mediated by G proteins sensitive to pertussis toxin. Surprisingly, treatment of synaptosomes with pertussis toxin alone increased the rate of glutamate uptake, while having no effect on uptake in the presence of riluzole. However, pretreatment with cholera toxin was found to completely block the effects of riluzole on glutamate uptake. These results reveal an additional mechanism by which riluzole can affect glutamatergic neurotransmission, and provides further support that riluzole may prove beneficial in the treatment of traumatic central nervous system injuries involving the excitotoxic actions of glutamate.

Riluzole improves measures of oxidative stress following traumatic spinal cord injury

Rats received a contusion injury to the spinal cord followed by treatment with riluzole (a glutamate release inhibitor, 8 mg/kg), methylprednisolone (MP 30 mg/kg) or both. At 4 h following injury, spinal cords were removed and synaptosomes prepared and examined using five measures of oxidative stress. Riluzole treatment was found to improve mitochondrial function, and enhance glutamate and glucose uptake. As expected, MP treatment was found to reduce lipid peroxidation, but also improved glutamate and glucose uptake. Interestingly, the combination treatment was found to be effective in improving all five measures of oxidative stress. The results of this study clearly demonstrate the potential beneficial effects of a combination approach in the treatment of oxidative stress events in traumatic spinal cord injury.

Vitamin D-receptor genotypes as independent genetic predictors of decreased bone mineral density in primary biliary cirrhosis

BACKGROUND & AIMS

Hepatic osteodystrophy is a complication of primary biliary cirrhosis (PBC). Allelic polymorphisms of the vitamin D receptor (VDR) gene are related to bone mineral density (BMD) in normal cohorts and those with primary osteoporosis. We sought to establish the prevalence of reduced bone mass in PBC, correlate BMD with VDR gene polymorphisms, and identify risk factors for the development of hepatic osteodystrophy.

METHODS

Seventy-two female patients with PBC were evaluated prospectively. Clinical information, BMD assessment, disease severity, and osteoporosis risk factors were documented, and multivariate regression modeling was performed.

RESULTS

Twenty-four percent of the patients were osteoporotic at the lumbar spine and 32% at the femur. Severe bone loss (z score <-2.0) occurs 4 times more frequently in patients with PBC compared with controls. Body weight (P = 0.003) and postmenopausal status (P = 0.012) correlated independently with BMD. VDR genotype (P = 0.01) correlated with lower BMD at the spine only.

CONCLUSIONS

Osteoporosis is a common complication of PBC. VDR genotype predicts lower BMD in patients with PBC. Studies are warranted to investigate the mechanism(s) by which VDR as well as other candidate genes may contribute to the development of hepatic osteodystrophy in PBC.

ALS-linked Cu/Zn-SOD mutation increases vulnerability of motor neurons to excitotoxicity by a mechanism involving increased oxidative stress and perturbed calcium homeostasis

We employed a mouse model of ALS, in which overexpression of a familial ALS-linked Cu/Zn-SOD mutation leads to progressive MN loss and a clinical phenotype remarkably similar to that of human ALS patients, to directly test the excitotoxicity hypothesis of ALS. Under basal culture conditions, MNs in mixed spinal cord cultures from the Cu/Zn-SOD mutant mice exhibited enhanced oxyradical production, lipid peroxidation, increased intracellular calcium levels, decreased intramitochondrial calcium levels, and mitochondrial dysfunction. MNs from the Cu/Zn-SOD mutant mice exhibited greatly increased vulnerability to glutamate toxicity mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors. The increased vulnerability of MNs from Cu/Zn-SOD mutant mice to glutamate toxicity was associated with enhanced oxyradical production, sustained elevations of intracellular calcium levels, and mitochondrial dysfunction. Pretreatment of cultures with vitamin E, nitric oxide-suppressing agents, peroxynitrite scavengers, and estrogen protected MNs from Cu/Zn-SOD mutant mice against excitotoxicity. Excitotoxin-induced degeneration of spinal cord MNs in adult mice was more extensive in Cu/Zn-SOD mutant mice than in wild-type mice. The mitochondrial dysfunction associated with Cu/Zn-SOD mutations may play an important role in disturbing calcium homeostasis and increasing oxyradical production, thereby increasing the vulnerability of MNs to excitotoxicity.

Activation of the caspase-3 apoptotic cascade in traumatic spinal cord injury

Traumatic spinal cord injury often results in complete loss of voluntary motor and sensory function below the site of injury. The long-term neurological deficits after spinal cord trauma may be due in part to widespread apoptosis of neurons and oligodendroglia in regions distant from and relatively unaffected by the initial injury. The caspase family of cysteine proteases regulates the execution of the mammalian apoptotic cell death program. Caspase-3 cleaves several essential downstream substrates involved in the expression of the apoptotic phenotype in vitro, including gelsolin, PAK2, fodrin, nuclear lamins and the inhibitory subunit of DNA fragmentation factor. Caspase-3 activation in vitro can be triggered by upstream events, leading to the release of cytochrome c from the mitochondria and the subsequent transactivation of procaspase-9 by Apaf-1. We report here that these upstream and downstream components of the caspase-3 apoptotic pathway are activated after traumatic spinal cord injury in rats, and occur early in neurons in the injury site and hours to days later in oligodendroglia adjacent to and distant from the injury site. Given these findings, targeting the upstream events of the caspase-3 cascade has therapeutic potential in the treatment of acute traumatic injury to the spinal cord.

BDNF and NT4/5 promote survival and neurite outgrowth of pontocerebellar mossy fiber neurons

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and NT4/5 are all found in the developing cerebellum. Granule cells, the major target neurons of mossy fibers, express BDNF during mossy fiber synaptogenesis. To determine whether neurotrophins contribute to the development of cerebellar afferent axons, we characterized the effects of neurotrophins on the growth of mossy fiber neurons from mice and rats in vitro. For a mossy fiber source, we used the basilar pontine nuclei (BPN), the major source of cerebellar mossy fibers in mammals. BDNF and NT4/5 increased BPN neuron survival, neurite outgrowth, growth cone size, and elongation rate, while neither NT3 nor NGF increased survival or outgrowth. In addition, BDNF and NT4/5 reduced the size of neurite bundles. Consistent with these effects, in situ hybridization on cultured basilar pontine neurons revealed the presence of mRNA encoding the TrkB receptor which binds both BDNF and NT4/5 with high affinity. We detected little or no message encoding the TrkC receptor which preferentially binds NT3. BDNF and NT4/5 also increased TrkB mRNA levels in BPN neurons. In addition to previously established functions as an autocrine/paracrine trophic factor for granule cells, the present results indicate that cerebellar BDNF may also act as a target-derived trophic factor for basilar pontine mossy fibers.

A rapid and sensitive assay for measuring mitochondrial metabolic activity in isolated neural tissue

In the present study, we used the oxidation-reduction sensitive dye Alamar Blue, a fluorometric/colorimetric indicator of metabolic activity, as a tool for examining mitochondrial function in rat spinal cord synaptosomes. At 15 min following incubation, Alamar Blue fluorescence levels were found to increase by 3-fold, and could be detected in samples containing as little as 25 microg of protein. Alamar Blue is non-toxic, making it possible to obtain measures of the metabolic rate and the maximal functional capacity of mitochondria in a single sample. The findings of this study demonstrate that Alamar Blue fluorescence levels increased in a near linear fashion when samples were measured every 15 min for a period of 1 h. To document that the changes in Alamar Blue fluorescence are directly related to mitochondrial function, synaptosomes were pre-incubated with antimycin A (10 microM) or malonate (50 mM), both of which are potent inhibitors of mitochondrial function. Pretreatment with either compound significantly reduced the Alamar Blue fluorometric signal at all time points examined. These results provide evidence that Alamar Blue is a valuable analytical tool for examining mitochondrial function in synaptosomal preparations from neural tissue. Moreover, the properties of Alamar Blue are such that it provides a more sensitive and simpler indicator compared to indicators used in existing assays.

Acute inflammatory response in spinal cord following impact injury

Numerous factors are involved in the spread of secondary damage in spinal cord after traumatic injury, including ischemia, edema, increased excitatory amino acids, and oxidative damage to the tissue from reactive oxygen species. Neutrophils and macrophages can produce reactive oxygen species when activated and thus may contribute to the lipid peroxidation that is known to occur after spinal cord injury. This study examined the rostral-caudal distribution of neutrophils and macrophages/microglia at 4, 6, 24, and 48 h after contusion injury to the T10 spinal cord of rat (10 g weight, 50 mm drop). Neutrophils were located predominantly in necrotic regions, with a time course that peaked at 24 h as measured with assays of myeloperoxidase activity (MPO). The sharpest peak of MPO activity was localized between 4 mm rostral and caudal to the injury. Macrophages/microglia were visualized with antibodies against ED1 and OX-42. Numerous cells with a phagocytic morphology were present by 24 h, with a higher number by 48 h. These cells were predominantly located within the gray matter and dorsal funiculus white matter. The number of cells gradually declined through 6 mm rostral and caudal to the lesion. OX-42 staining also revealed reactive microglia with blunt processes, particularly at levels distant to the lesion. The number of macrophages/microglia was significantly correlated with the amount of tissue damage at each level. Treatments to decrease the inflammatory response are likely to be beneficial to recovery of function after traumatic spinal cord injury.

Localization of glial cell line-derived neurotrophic factor receptor alpha and c-ret mRNA in rat central nervous system

Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophic factor that influences the survival and function of several neuronal populations in the central (CNS) and peripheral nervous systems. The actions of GDNF are mediated by a multicomponent receptor complex composed of the tyrosine kinase product of c-ret and the ligand-binding protein GDNF receptor alpha (GDNFR-alpha). In the present study, we used in situ hybridization to localize cells expressing the mRNA for these GDNF receptor subunits in rat CNS. As reported previously, GDNFR-alpha and c-ret mRNA are present in the substantia nigra and ventral tegmental area, regions containing GDNF-responsive dopamine neurons. However, both mRNA were found in motor neurons of spinal cord and brainstem nuclei that innervate skeletal muscle. These areas include alpha motor neurons in the ventral horn of spinal cord and neurons in hypoglossal, facial, trigeminal, and abducens nuclei. In areas rostral to the substantia nigra, c-ret mRNA is not detected, whereas GDNFR-alpha is found in numerous brain structures, including the hippocampus, cortex, medial geniculate, and the medial habenula, the latter area expressing the highest levels of GDNFR-alpha mRNA in brain. These results provide evidence that c-ret and GDNFR-alpha mRNA are expressed in neuronal populations involved in motor function and provides further support for GDNF as a target-derived neurotrophic for these motor neurons. The observation that GDNFR-alpha mRNA is localized in several brain structures that do not contain detectable levels of c-ret mRNA indicates that either GDNFR-alpha utilizes signal transduction molecules other than c-ret in these areas or that other GDNF-like ligands that utilize GDNFR-alpha as a receptor may be present.

Rapid calpain I activation and cytoskeletal protein degradation following traumatic spinal cord injury: attenuation with riluzole pretreatment

Immunocytochemical and immunoblotting techniques were used to investigate calpain I activation and the stability of the calpain-sensitive cytoskeletal proteins microtubule-associated protein 2 (MAP2) and spectrin at 1, 4, and 24 h after contusion injury to the spinal cord. Spinal cord injury resulted in the activation of calpain I at all time points examined, with the highest level of activation occurring at 1 h. At the same early time point, there was a loss of dendritic MAP2 staining in spinal cord sections, accompanied by pronounced perikaryal accumulation. The loss in MAP2 staining in the injured spinal cord progressed over the 24-h survival period to affect regions 3 mm distant to the site of injury. The presence of calpain I-specific spectrin degradation was apparent in neuronal cell bodies and fibers as early as 1 h after injury, with the most intense staining occurring within and juxtaposed to the injury site. Spectrin breakdown products in neuronal cell bodies declined rapidly at 4 h and were nearly undetectable at 24 h after injury. Immunoblot studies confirmed the immunocytochemical results by demonstrating a significant increase in calpain I activation, a significant decrease in MAP2 levels, and a significant increase in spectrin breakdown. Finally, treatment of animals with riluzole, an inhibitor of glutamate release, before surgery reduced significantly the loss of MAP2 levels observed at 24 h after injury. These results demonstrate that Ca2+-dependent protease activation and degradation of critical cytoskeletal proteins are early events after spinal cord injury and that treatments that minimize the actions of glutamate may limit their breakdown.

Rapid calpain I activation and cytoskeletal protein degradation following traumatic spinal cord injury: attenuation with riluzole pretreatment

Immunocytochemical and immunoblotting techniques were used to investigate calpain I activation and the stability of the calpain-sensitive cytoskeletal proteins microtubule-associated protein 2 (MAP2) and spectrin at 1, 4, and 24 h after contusion injury to the spinal cord. Spinal cord injury resulted in the activation of calpain I at all time points examined, with the highest level of activation occurring at 1 h. At the same early time point, there was a loss of dendritic MAP2 staining in spinal cord sections, accompanied by pronounced perikaryal accumulation. The loss in MAP2 staining in the injured spinal cord progressed over the 24-h survival period to affect regions 3 mm distant to the site of injury. The presence of calpain I-specific spectrin degradation was apparent in neuronal cell bodies and fibers as early as 1 h after injury, with the most intense staining occurring within and juxtaposed to the injury site. Spectrin breakdown products in neuronal cell bodies declined rapidly at 4 h and were nearly undetectable at 24 h after injury. Immunoblot studies confirmed the immunocytochemical results by demonstrating a significant increase in calpain I activation, a significant decrease in MAP2 levels, and a significant increase in spectrin breakdown. Finally, treatment of animals with riluzole, an inhibitor of glutamate release, before surgery reduced significantly the loss of MAP2 levels observed at 24 h after injury. These results demonstrate that Ca2+-dependent protease activation and degradation of critical cytoskeletal proteins are early events after spinal cord injury and that treatments that minimize the actions of glutamate may limit their breakdown.

Impaired mitochondrial function, oxidative stress and altered antioxidant enzyme activities following traumatic spinal cord injury

Glutamate-induced excitotoxicity involving the formation of reactive oxygen species (ROS) has been implicated in neuronal dysfunction and cell loss following ischemic and traumatic injury to the central nervous system (CNS). ROS are formed in mitochondria when energy metabolism is compromised, and are inactivated by the ROS scavengers superoxide dismutase (SOD), catalase, and glutathione (GSH). ROS can impair the function of several cellular components including proteins, nucleic acids, and lipids. In the present study, we measured indicators of mitochondrial metabolic activity, ROS formation, lipid peroxidation, and antioxidant enzyme activities in synaptosomes obtained from rat spinal cord at early times following traumatic injury. Mitochondrial metabolic activity was found to significantly decrease as early as 1 h following injury, and continued to be compromised over the remaining postinjury time points. ROS formation was found to be significantly increased at 4 and 24 h following injury, while lipid peroxidation levels were found to be significantly increased in the injured spinal cord at 1 and 24 h, but not 4 h following injury. SOD enzyme activity was unchanged at all postinjury time points, while catalase activity and GSH levels were significantly increased at 24 h following injury. These findings indicate that impaired mitochondrial function, ROS, and lipid peroxidation occur soon after traumatic spinal cord injury, while the compensatory activation of molecules important for neutralizing ROS occurs at later time points. Therapeutic strategies aimed at facilitating the actions of antioxidant enzymes or inhibiting ROS formation and lipid peroxidation in the CNS may prove beneficial in treating traumatic spinal cord injury, provided such treatments are initiated at early stages following injury.

FAC1 expression and localization in motor neurons of developing, adult, and amyotrophic lateral sclerosis spinal cord

In this study we report the localization and expression of FAC1 protein in developing, normal adult and amyotrophic lateral sclerosis (ALS) lumbar spinal cord. High levels of FAC1 protein were detected in cells throughout all areas (gray and white matter) of the developing lumbar spinal cord. FAC1 protein was localized predominately in nuclei and the cell body of motor neurons during early stages of spinal cord development. In contrast, low levels of FAC1 protein were observed in the adult lumbar spinal cord, localized only in the cell body of large alpha motor neurons found in lamina IX. Interestingly, FAC1 protein expression was elevated in surviving motor neurons of ALS spinal cord compared to the controls and was located both in the nucleus and throughout the cytoplasm of motor neurons. FAC1 protein was also observed in white matter cells and fibers in ALS spinal cord. In support of the immunocytochemical results, in situ hybridization studies demonstrated that FAC1 mRNA is also elevated in ALS spinal cord motor neurons. These data describe the developmental regulation of FAC1 protein in the spinal cord by immunocytochemical techniques and provide evidence that this protein is reexpressed in ALS motor neurons.

Endogenous glutamate levels regulate nerve growth factor mRNA expression in the rat dentate gyrus

The levels of nerve growth factor (NGF) mRNA can be regulated in vitro and in vivo in the hippocampal formation by events associated with pharmacological activation of glutamate receptors. In the present study, the level of NGF mRNA in the hippocampal formation was examined following an intrahippocampal injection of 1 nmole fluorocitrate, which temporarily inhibits the astrocyte metabolic activity in vivo. Consistent with previous findings, fluorocitrate treatment significantly increased glutamate levels and decreased glutamine levels in the dentate gyrus as determined by in vivo microdialysis. The increased ratio of glutamate to glutamine was followed by a significant increase in NGF mRNA expression selectively in dentate gyrus granule cells. The effects of increasing glutamate levels were blocked by pretreatment with 50 nmole 2-amino-5-phosphonovalerate (AP5), a competitive antagonist that acts at the N-methyl-D-aspartate (NMDA) glutamate receptor subtype. These findings suggest that NGF mRNA expression is regulated, in part, by changes in endogenous glutamate levels, partially through enhanced excitatory neurotransmission through NMDA receptors.

4-hydroxynonenal, a lipid peroxidation product, rapidly accumulates following traumatic spinal cord injury and inhibits glutamate uptake

Traumatic injury to the spinal cord initiates a host of pathophysiological events that are secondary to the initial insult. One such event is the accumulation of free radicals that damage lipids, proteins, and nucleic acids. A major reactive product formed following lipid peroxidation is the aldehyde, 4-hydroxynonenal (HNE), which cross-links to side chain amino acids and inhibits the function of several key metabolic enzymes. In the present study, we used immunocytochemical and immunoblotting techniques to examine the accumulation of protein-bound HNE, and synaptosomal preparations to study the effects of spinal cord injury and HNE formation on glutamate uptake. Protein-bound HNE increased in content in the damaged spinal cord at early times following injury (1-24 h) and was found to accumulate in myelinated fibers distant to the site of injury. Immunoblots revealed that protein-bound HNE levels increased dramatically over the same postinjury interval. Glutamate uptake in synaptosomal preparations from injured spinal cords was decreased by 65% at 24 h following injury. Treatment of control spinal cord synaptosomes with HNE was found to decrease significantly, in a dose-dependent fashion, glutamate uptake, an effect that was mimicked by inducers of lipid peroxidation. Taken together, these findings demonstrate that the lipid peroxidation product HNE rapidly accumulates in the spinal cord following injury and that a major consequence of HNE accumulation is a decrease in glutamate uptake, which may potentiate neuronal cell dysfunction and death through excitotoxic mechanisms.

Altered expression of bcl-2 and bax mRNA in amyotrophic lateral sclerosis spinal cord motor neurons

One of the primary neurodegenerative events occurring in amyotrophic lateral sclerosis (ALS) is the selective loss of spinal cord alpha motor neurons. To study the potential role of apoptosis in the degeneration of these motor neurons, in situ hybridization was used to measure the expression of two apoptotic cell death genes, bcl-2 and bax, in control and ALS lumbar spinal cord sections. The strongest hybridization signal for bcl-2 mRNA in neurological and nonneurological control spinal cords was found primarily in lamina IX alpha motor neurons, while a weaker hybridization signal was found in neurons of Clarke's nucleus and the proper sensory nucleus of the dorsal horn. Surviving lamina IX motor neurons in ALS spinal cord sections also expressed bcl-2 mRNA, but at levels that were significantly and selectively decreased (4.7-fold) compared with controls. bax mRNA hybridization signal was detected in several cells throughout the gray matter in control and ALS lumbar spinal cord, but was significantly and selectively increased (2.8-fold) in ALS motor neurons. Given the proposed interactive roles of these genes in apoptosis, the present findings favor a scenario in which this mode of cell death would contribute to spinal cord motor neuron degeneration in ALS.

cDNA sequence and differential mRNA regulation of two forms of glial cell line-derived neurotrophic factor in Schwann cells and rat skeletal muscle

Total RNA from rat Schwann cells grown in culture and adult rat skeletal muscle was reverse transcribed, amplified for glial cell line-derived neurotrophic factor (GDNF) messenger RNA (mRNA) using the polymerase chain reaction (PCR), and the PCR products sequenced. Two forms of GDNF were detected in the PCR step, one of a predicted size (GDNF633) and a second smaller form missing a 78-base pair sequence (GDNF555). Sequence analysis demonstrated that GDNF633 is similar to the published sequence of GDNF differing only at three nucleotides. Southern and Northern blot analyses reveal that the two forms are probably derived from a single RNA species that is alternatively spliced. Interestingly, GDNF633 mRNA was found to be selectively upregulated in denervated rat skeletal muscle at 1-2 weeks following axotomy, providing evidence that the innervation status of the muscle may determine the expression profile of the two alternatively spliced forms. Given these findings, we suggest that GDNF may function as a target-derived trophic factor for neuronal populations innervating skeletal muscle, including sensory neurons and spinal cord motoneurons.

Expression of GDNF mRNA in rat and human nervous tissue

A recently cloned neurotrophic factor, termed glial cell line-derived neurotrophic factor (GDNF), has been reported to exhibit selective neurotrophic properties on ventral mesencephalon dopaminergic neurons, which degenerate in patients with Parkinson's disease. In the present study, we used reverse transcriptase followed by polymerase chain reaction (PCR) and in situ hybridization to study the expression of GDNF messenger RNA (mRNA) in the adult rat and human central nervous system (CNS). GDNF transcripts were identified using PCR in all regions of the rat CNS analyzed including striatum, hippocampus, cortex, cerebellum, and spinal cord. Interestingly, the rat hippocampal formation contained two transcripts, i.e., a larger form in addition to the amplified GDNF cDNA found in all other areas analyzed. GDNF PCR products also were observed in human striatum, hippocampus, cortex, and spinal cord, but not cerebellum, and both the striatum and hippocampal formation contained two GDNF transcripts. Finally, GDNF transcripts were detected in a rat Schwann cell line previously shown to secrete a factor that exerts a neurotrophic effect on dopaminergic neurons. In situ hybridization experiments using a cRNA probe hybridized to adult rat brain sections demonstrated no positive GDNF mRNA signal. However, intense GDNF mRNA hybridization signal was found to be associated with dorsal root ganglia in Postnatal Day 1 rats. These findings provide evidence that GDNF is detectable using PCR in a number of nervous system structures and, in some areas, GDNF is expressed in more than one form.

Neurotrophic factor mRNA expression in dentate gyrus is increased following angular bundle transection

In the central nervous system, the highest levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA are found in the hippocampal formation. In the present study, we report that a unilateral transection of the angular bundle, which relays cortical information via the entorhinal cortex to the hippocampal formation, increases NGF and BDNF mRNA in the ipsilateral dentate gyrus. Within 4 hours following transection, the hybridization signal for NGF and BDNF mRNA increases in stratum granulosum 3- and 5-fold, respectively, compared to control levels. This lesion-induced increase of both mRNA returns to control levels within 24 hours and is maintained for at least 5 days. The induction is not prevented by pretreatment with AP-5, CNQX, or cholinergic denervation due to transection of the fimbria-fornix. Finally, the induction of neurotrophin mRNA is preceded by an increase in c-fos mRNA. These results provide evidence that transection of the cortical input to the hippocampal formation upregulates NGF and BDNF mRNA selectively in stratum granulosum. We suggest that the increased expression of NGF and BDNF mRNA may be an early step in the synaptic rearrangement of neurotrophin responsive cholinergic afferents observed following damage to the entorhinal cortex.

Neurotrophic factor mRNA expression in dentate gyrus is increased following in vivo stimulation of the angular bundle

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two structurally-related neurotrophins synthesized in dentate gyrus granule cells and pyramidal neurons of the hippocampal formation. These neurons receive excitatory glutamatergic afferents from the entorhinal cortex via the angular bundle/perforant path. In the present study, we tested whether electrophysiological stimulation of this glutamatergic pathway modifies NGF or BDNF messenger RNA (mRNA) expression in vivo. Within hours following brief trains of high frequency angular bundle stimulation, the levels of mRNA encoding both neurotrophins were increased exclusively in granule cells of the ipsilateral dentate gyrus. The increase in neurotrophic factor mRNA expression was found to be mediated through the N-methyl-D-aspartate (NMDA) glutamate receptor subtype, and occurred in the absence of seizure. These findings provide evidence that neurotrophic factor mRNA levels in the hippocampal formation are increased by direct activation of excitatory afferents originating in the entorhinal cortex. We suggest that the function of some neurotrophin-responsive neuronal populations may depend upon the integrity and activity of neurons in the entorhinal cortex, a population of neurons reported to be compromised in patients with Alzheimer's disease.

Activation of NMDA receptors increases brain-derived neurotrophic factor (BDNF) mRNA expression in the hippocampal formation

In the present study, it is demonstrated that activation of NMDA receptors upregulates brain-derived neurotrophic factor (BDNF) in granule cells of the dentate gyrus and CA3 pyramidal neurons. BDNF mRNA levels in the granule cells peaked within 4 h, were still evident at 24 h, and returned to control levels within 48 h. In the CA3 region, BDNF mRNA levels were significantly increased at 2 h, peaked at 4 h, and returned to control values by 8 h following NMDA treatment. Finally, the effects of NMDA on BDNF mRNA expression were blocked by AP5, an NMDA receptor antagonist. These findings provide evidence that the in vivo activation of NMDA receptors may regulate the expression of this neurotrophin.

Experimental rationale for the therapeutic use of neurotrophins in amyotrophic lateral sclerosis

Current therapeutic efforts to treat chronic and progressive neurodegenerative disease include, for the first time, attempts to regenerate affected nervous tissue using neurotrophic factors. The rationale for using trophic factors includes the understanding that they support neuronal survival and regrowth processes. The potential benefits of trophic factor therapy will be no more realized in the near future than in the treatment of amyotrophic lateral sclerosis (ALS). ALS is pathologically characterized by the selective degeneration of specific populations of cranial and spinal motoneurons. Evidence for the existence of factors that support motoneurons has come from studies demonstrating that motoneurons receive trophic influences from various tissues, both central and peripheral, within their local environment. Although the identity of these putative tissue-derived factors has remained enigmatic, recent studies have demonstrated that several previously characterized trophic factors exhibit trophic influences on motoneurons. Among these are several members of the neurotrophin family, most notably brain-derived neurotrophic factor. These neurotrophins meet most of the criteria to be considered motoneuron trophic factors: they are locally available to motoneurons in vivo; motoneurons express specific receptors for these factors; and exogenous application of these factors mimicks the effects of the uncharacterized endogenous agents. The clinical use of these factors for the treatment of ALS, therefore, appears to be scientifically justified.

Experimental evidence for growth factor treatment and function in certain neurological disorders

This issue focuses on the potential utilization or involvement of growth factors in Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and epilepsy. Certainly, the role of growth factors in other neurological disorders associated with stroke, trauma, and neurodegeneration needs to be considered. While there is no direct evidence to indicate that a neurological disorder is associated with the compromised function of a specific growth factor, the use of these molecules as therapeutic agents is justifiable. Undoubtedly, the outcome of current clinical trials will certainly influence future decisions on the use of growth factor therapies.

Spinal cord motoneurons express p75NGFR and p145trkB mRNA in amyotrophic lateral sclerosis

In the present study, in situ hybridization was used to examine the expression of nerve growth factor (NGF) receptor (p75NGFR), trk (p140trk) and trkB (p145trkB) mRNA in spinal cord sections from patients with amyotrophic lateral sclerosis (ALS). We report that the expression of p75NGFR and p145trkB mRNA is elevated in alpha motoneurons in ALS sections. However, p140trk mRNA was not expressed in either ALS or control sections.

Regulation of nerve growth factor mRNA in the hippocampal formation effects of N-methyl-D-aspartate receptor activation

In the hippocampal formation, nerve growth factor (NGF) is produced in granule cells of the dentate gyrus and a few pyramidal cells of Ammon's horn. Both neuronal populations express N-methyl-D-aspartate (NMDA) receptors and receive putative glutamatergic afferents originating in the entorhinal cortex and projecting via the perforant path. We report in this study that intra-hippocampal or intraventricular injections of NMDA increase NGF mRNA levels in dentate gyrus granule cells as determined using in situ hybridization histochemistry and a solution hybridization assay. NGF mRNA induction is detected within 2 h following NMDA treatment and returns to control levels within 24 h. This NMDA effect is dose-dependent and blocked by pretreatment with 2-amino-5-phosphonopentanoic acid, a competitive NMDA antagonist. Finally, the induction of NGF mRNA is observed in the absence of detectable neurotoxicity or seizure activity. We postulate that normal physiological events associated with the activation of hippocampal NMDA receptors may regulate mRNA expression of this neurotrophic factor.

Co-grafts of embryonic dopamine neurons and adult sciatic nerve into the denervated striatum enhance behavioral and morphological recovery in rats

We have recently demonstrated that a diffusible factor(s) derived from explanted adult rat sciatic nerve can increase the number and neurite outgrowth of embryonic rat dopamine (DA) neurons in culture. The present study extends this finding to compare DA neuron-sciatic nerve co-grafts to grafts of DA-rich neural tissue alone for behavioral and morphological effects in rats with unilateral nigrostriatal lesions of the DA pathway. Our results indicate that the presence of a co-grafted segment of sciatic nerve increased the likelihood of rapid behavioral recovery and promoted complete recovery mediated by small grafts that yielded only modest behavioral changes in the absence of co-grafted nerve. These behavioral effects were accompanied by a modest increase in survival of grafted tyrosine hydroxylase-positive neurons in the striatum and a more pronounced increase in the area and density of striatal reinnervation provided by grafted DA neurons in co-grafted animals. This evidence supports the view that a diffusible product of explanted peripheral nerve acts as a growth-promoting factor for embryonic DA neurons and that the presence of this factor augments the behavioral efficacy of grafted DA neurons.

Non-radioactive detection of nerve growth factor receptor (NGFR) mRNA in rat brain using in situ hybridization histochemistry

Radioactively labeled RNA probes in conjunction with in situ hybridization histochemistry have become a useful method for studying gene expression in the central nervous system. We used digoxigenin-labeled uridine triphosphate to synthesize cRNA probes for localization of nerve growth factor receptor (NGFR) mRNA in the rat basal forebrain. Detection of cells containing digoxigenin-labeled NGFR mRNA was accomplished using a digoxigenin antibody conjugated with alkaline phosphatase. NGFR mRNA-positive cells were distributed in three major cell groups in the basal forebrain: the medial septal nucleus, vertical and horizontal limbs of the diagonal band of Broca, and nucleus basalis. This technique provides a rapid and sensitive method for high-resolution detection of mRNA species in the central nervous system, as well as the potential for co-localization of two different mRNA species within individual cells.

Diffusible factor(s) from adult rat sciatic nerve increases cell number and neurite outgrowth of cultured embryonic ventral mesencephalic tyrosine hydroxylase-positive neurons

Dissociated embryonic rat ventral mesencephalon containing the developing A8-A10 dopamine (DA) neurons was cultured alone or in the presence of a 10 mm segment of adult rat sciatic nerve that had been explanted and maintained in separate culture for 72 hours prior to introduction to mesencephalic cultures. Nerve segments were contained in a co-culture basket, so that midbrain cells and nerve shared medium but were not in physical contact. The number and morphology of cultured DA neurons was assessed via immunocytochemistry for tyrosine hydroxylase (TH). Co-cultures of ventral midbrain tissue and nerve exhibited an increased number of TH-positive neurons, with larger neuronal perikarya, and increased length and complexity of neurites, than cultures of midbrain tissue alone. Increased number and growth of TH-positive neurons was obtained with as little as 2 days of exposure to nerve. This evidence suggests that a diffusible, soluble factor(s) from sciatic nerve can enhance the number and development of TH-positive neurons detected in cultures of embryonic ventral mesencephalon.

Localization of nerve growth factor receptor mRNA in the rat basal forebrain with in situ hybridization histochemistry

1. In situ hybridization histochemistry was used to localize nerve growth factor receptor (NGFR) mRNA in the adult rat basal forebrain. 2. In emulsion-dipped sections 35S-labeled RNA antisense probes produced a high density of silver grains over cells located in the medial septum, vertical and horizontal limbs of the diagonal band of Broca, and nucleus basalis. 3. This distribution of NGFR mRNA overlaps with the distribution of NGFR protein localized using immunocytochemical techniques. 4. No hybridization signal was detected when sections were hybridized with a 35S-labeled RNA sense (control) probe. 5. We suggest that NGFRs are synthesized in these basal forebrain nuclei and transported to terminal areas where NGF is thought to be bound and internalized, an initial step in the many actions of this neurotrophic factor.

The use of hollow polymer fibers for the delivery of bioactive molecules to the brain

Experimental studies have provided evidence that bioactive molecules can be delivered to the central nervous system through the use of hollow polymer fibers. These implantable fibers can be used for the delivery of peptide solutions or serve as a carrier device for encapsulating tissue preparations and cell suspensions. This commentary will address the use of these polymer fibers as a potential therapeutic strategy for treating neurodegenerative disorders such as Alzheimer's disease.

Nerve growth factor receptors in the central nervous system

Nerve growth factor (NGF) is well known to be involved in the development, survival, and maintenance of sympathetic and neural crest-derived sensory neurons in the peripheral nervous system. Over the last 10-15 years, however, the role of NGF as a necessary trophic substrate for magnocellular cholinergic neurons in the central nervous system (CNS) has emerged. Because the trophic effects of NGF are initiated by its interaction with membrane-bound receptors, the characterization, localization, and function of these specific NGF receptors are essential to understanding the many actions of NGF. The first part of this review will summarize briefly the presence and possible role of NGF in the CNS, with the remainder of the review focusing on what is known about the receptor to NGF.

Transplantation of male mouse submaxillary gland increases survival of axotomized basal forebrain neurons

Transection of the fimbria-fornix results in a loss of magnocellular neurons in the medial septum and vertical limb of the diagonal band (MS/VDB), possibly due to the deprivation of a retrogradely transported trophic substance, such as nerve growth factor (NGF), derived from the hippocampal formation. We have utilized a transplantation model in which grafts of NGF-rich male mouse submaxillary gland were placed in the lateral ventricle adjacent to the MS/VDB of rats with transections of the fimbria-fornix. At 2-4 weeks following transection, animals with grafted submaxillary glands exhibited enhanced survival of MS/VDB neurons, which stained positive for acetylcholinesterase and were immunoreactive for the NGF receptor. These experiments demonstrate that grafts of male mouse submaxillary gland can facilitate the survival of axotomized MS/VDB cholinergic neurons and may therefore prove beneficial in promoting regeneration of damaged neural systems.

Regional analysis of age-related changes in the cholinergic system of the hippocampal formation and basal forebrain of the rat

In an attempt to clarify conflicting reports of age-related changes in cholinergic systems of the rat hippocampal formation and basal forebrain, we compared aged (40 months) and adult (12 months) male rats using quantitative, regional receptor autoradiography in addition to radiolabelled assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). The activities of ChAT and AChE in Ammon's horn/subiculum are 24% and 38% lower, respectively, in the aged brains. There is also a drop in both ChAT (38%) and AChE (28%) activities in the septum, and a 46% drop in ChAT activity in the nucleus basalis of aged rats. In the septal pole of the hippocampal formation there is no significant change with age in binding of the muscarinic antagonist, tritiated quinuclidinyl benzylate (3H-QNB) in any hippocampal subregion. However, specific binding in the temporal pole is higher in the subiculum (40%), CA (27%), and dentate gyrus (25%) of the aged animals. Because some of the neurons of the diagonal band of Broca project to the temporal areas of the hippocampal formation by way of a ventral pathway, it is possible that with age this septohippocampal pathway is selectively affected. Particularly in Ammon's horn and the subicular regions of the aged rat hippocampus, postsynaptic muscarinic receptors may upregulate to compensate for decreases in presynaptic cholinergic activity.

Demonstration of the retrograde transport of nerve growth factor receptor in the peripheral and central nervous system

NGF acts on responsive neurons by binding to specific NGF receptors on axonal termini, after which a critical biochemical signal is retrogradely transported to the cell body. The identity of the signal(s) is unknown; candidates include NGF itself or some other "second messenger." A possible second messenger is the NGF receptor. As a first step in assessing the possible role of NGF receptor in the generation of the NGF-dependent signal, and in understanding the economy of NGF receptor synthesis and utilization, we determined whether the NGF receptor is retrogradely transported. Using immunohistochemical staining with a monoclonal antibody (192-IgG) against rat NGF receptor, we looked for accumulation of NGF receptor molecules distal (retrograde transport), as well as proximal (anterograde transport), to sites of axonal ligation or transection. By 10-12 hr in both the ligated sciatic nerve and the lesioned fimbria-fornix, accumulated NGF receptor was detected proximal and distal to the ligation/lesion site. The transported receptor presumably was located in sympathetic and sensory neurons in the sciatic nerve and in forebrain cholinergic neurons projecting from the medial septum to the hippocampus. In both anatomical sites, accumulation of NGF receptor on the proximal (anterograde) side occurred in streams of fine axonal processes, whereas staining on the distal (retrograde) side occurred in varicose or granular configurations. These results raise the possibility that the NGF receptor has a role in the mechanism of NGF beyond the initial binding event at the plasma membrane of the axonal terminus.

Basal forebrain magnocellular neurons stain for nerve growth factor receptor: correlation with cholinergic cell bodies and effects of axotomy

Recent evidence has demonstrated the presence of nerve growth factor (NGF) in areas of the central nervous system characterized by cholinergic innervation. We report that a unique population of rat basal forebrain magnocellular neurons that project to the cortex and hippocampus are immunoreactive to a monoclonal antibody to the NGF receptor. Removal of target contact results in a time-dependent loss or shrinkage of cells in the basal forebrain that stain for NGF receptor and acetylcholinesterase, suggesting that under normal conditions, basal forebrain cholinergic neurons utilize NGF for trophic support.

Intrahippocampal injections of antiserum to nerve growth factor inhibit sympathohippocampal sprouting

Following lesions of the fimbria/fornix system in the rat, noradrenergic sympathetic fibers grow into the hippocampal formation. It has been postulated that these fibers collateralize in response to the presence of a neurotrophic substance similar to Nerve Growth Factor (NGF). We tested this by injecting into the rat hippocampus antibody to NGF, or control serum (contralateral control), immediately prior to a bilateral fimbria/fornix transection. In fluorescent histochemical preparations at four to five weeks following surgery, there are fewer large, brightly fluorescent fibers around the injection site on the experimental side when compared with the contralateral control side. These results support the hypothesis that NGF, or an NGF-like substance, plays an important role in the sprouting of sympathetic fibers into the denervated hippocampal formation.

Suppression of corticosterone synthesis alters the behavior of hippocampally lesioned rats

The suppression of corticosterone synthesis with metyrapone (25 mg/kg) reduced the hyperactivity and altered the exploratory activity of hippocampally lesioned animals (HPC) in the open field to the level of cortical and sham controls (Experiment 1). In a second experiment, corticosterone (600 micrograms/kg) pretreatment 2 h, but not 1 h, before metyrapone partially restored the hyperactivity of HPC animals that had been decreased by the corticosteroid-suppressant drug. Alterations in exploratory behavior induced by metyrapone were also prevented by corticosterone pretreatment. The results suggest that the suppression of corticosterone in hippocampally lesioned animals produces a normalization of behavior that can be prevented by pretreatment with corticosterone.

Differentiation of basal ganglia dopaminergic involvement in behavior after hippocampectomy

Large bilateral aspiration lesions of the hippocampus in rats lead to a variety of changes in spontaneous behavior measured in an open field/hole board, relative to sham and neocortically lesioned controls. These changes include increased locomotion, and decreased grooming frequency and rearing bout duration. When animals were injected with the dopamine (DA) agonist 3,4-dihydroxyphenylamino-2-imidazoline (DPI: 0.5, 1.0 and 5.0 microgram) into the nucleus accumbens one week after surgery, the behavior of hippocampally lesioned rats was restored to levels not different from control lesioned rats. Haloperidol injections (0.05, 0.1 and 0.5 microgram) into the caudate nucleus were not able to do this. Further, DPI injected into the caudate month after surgery was also able to attenuate some of the effects of hippocampal damage. On the other hand, haloperidol injections into the nucleus accumbens did not influence behavior. The results are interpreted in terms of hippocampal lesion-induced alteration of a balance in basal ganglia DA systems, indicated by modified response to pharmacological intervention and which mediate the behavioral effects of the lesion.

Dopamine depletion in nucleus accumbens reduces ACTH1-24-induced excessive grooming

Animals were pretreated with 6-OHDA or ascorbate vehicle injected into the nucleus accumbens and tested 10 days later for excessive grooming induced by intracerebroventricular injection of ACTH1-24. The animals pretreated with 6-OHDA showed a significant decrease in excessive grooming produced by the neuropeptide and this reduction was seen only in the last 30 minutes of a 60-min test session. The results suggest an interaction of ACTH with dopamine systems on the onset and maintenance of excessive grooming.

Catecholamine alterations in basal ganglia after hippocampal lesions

Rats were given sham, cortical, or hippocampal lesions and sacrificed 7 or 28 days following surgery. Levels of norepinephrine, dopamine, and the major dopamine metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA), were assayed in 3 brain regions. At day 7 there was a decrease in dopamine utilization and a decrease in norepinephrine levels in the nucleus accumbens after hippocampal damage but both of these measures returned to normal levels by day 28. In the neostriatum HVA levels decreased at day 7 after hippocampal damage. The utilization of dopamine in the neostriatum was decreased at day 28 in animals that received neocortical lesions but this was not observed in animals with hippocampal destruction. No effects of any lesion at any day were found in the olfactory tubercle region, the third brain region analyzed. It is thought that the removal of hippocampal and neocortical input to the basal ganglia influences catecholamine function reflected in the loss and subsequent recovery of dopamine utilization.

Behavioral assessment of norepinephrine and serotonin function and interaction in the hippocampal formation

Norepinephrine (NE) and serotonin (5-HT) were injected either into the dorsal or ventral hippocampal formation of rats in doses ranging from 0.005 microgram/microliter to 5.0 microgram/microliter. Behavioral reactivity was assessed by recording latency to paw lick when placed on a hot plate and magnitude of force displaced in a vertical direction to a footshock. In addition open field activity was measured. NE injections resulted in a dose-dependent increase in behavioral reactivity to the hot plate and footshock; 5-HT injections resulted in a dose-dependent decrease in behavioral reactivity to hot plate and footshock. Both NE and 5-HT injections resulted in a dose-dependent increase in open field activity. NE injections were more effective in increasing reactivity when injected into the dorsal hippocampus while 5-HT injections were more effective in decreasing behavioral reactivity when injected into the ventral hippocampus. Both NE and 5-HT were most effective in increasing open field behavior, however, when injected into the dorsal hippocampus. When NE and 5-HT were injected simultaneously they resulted in no change in behavioral reactivity as compared to saline injections. Simultaneous injections of NE and 5-HT neither enhanced nor antagonized the increase in open field activity of each amine injected alone. The results are discussed in terms of the functional significance of NE and 5-HT in the hippocampus, their modes of action and significance for understanding dorsal-ventral hippocampal differences.