Behavioral effects of chronic melatonin and pregnenolone injections in a myelin mutant rat (taiep)

Long-term taurine administration improves motor skills in a tubulinopathy rat model by decreasing oxidative stress and promoting myelination

The taiep rat undergoes hypomyelination and progressive demyelination caused by an abnormal microtubule accumulation in oligodendrocytes, which elicits neuroinflammation and motor behavior dysfunction. Based on taurine antioxidant and proliferative actions, this work explored whether its sustained administration from the embryonic age to adulthood could prevent neuroinflammation, stimulate cell proliferation, promote myelination, and relieve motor impairment. Taurine (50 mg/L of drinking water = 50 ppm) was given to taiep pregnant rats on gestational day 15 and afterward to the male offspring until eight months of age. We measured the levels of nitric oxide (NO), malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA), CXCL1, CXCR2 receptor, growth factors (BNDF and FGF2), cell proliferation, and myelin content over time. Integral motor behavior was also evaluated. Our results showed that taurine administration significantly decreased NO and MDA + 4-HDA levels, increased cell proliferation, and promoted myelination in an age- and brain region-dependent fashion compared with untreated taiep rats. Taurine effect on chemokines and growth factors was also variable. Taurine improved vestibular reflexes and limb muscular strength in perinatal rats and fine movements and immobility episodes in adult rats. These results show that chronic taurine administration partially alleviates the taiep neuropathology.

Age-related changes and effects of regular low-intensity exercise on gait, balance, and oxidative biomarkers in the spinal cord of Wistar rats

The present study aimed to analyze age-related changes to motor coordination, balance, spinal cord oxidative biomarkers in 3-, 6-, 18-, 24-, and 30-month-old rats. The effects of low-intensity exercise on these parameters were also analyzed in 6-, 18-, and 24-month-old rats. Body weight, blood glucose, total cholesterol, and high-density lipoprotein (HDL) cholesterol were assessed for all rats. The soleus muscle weight/body weight ratio was used to estimate skeletal muscle mass loss. Body weight increased until 24 months; only 30-month-old rats exhibited decreased blood glucose and increased total cholesterol and HDL cholesterol. The soleus muscle weight/body weight ratio increased until 18 months, followed by a small decrease in old rats. Exercise did not change any of these parameters. Stride length and step length increased from adult to middle age, but decreased at old age. Stride width increased while the sciatic functional index decreased in old rats. Performance in the balance beam test declined with age. While gait did not change, balance improved after exercise. Aging increased superoxide anion generation, hydrogen peroxide levels, total antioxidant capacity, and superoxide dismutase activity while total thiol decreased and lipid hydroperoxides did not change. Exercise did not significantly change this scenario. Thus, aging increased oxidative stress in the spinal cord, which may be associated with age-induced changes in gait and balance. Regular low-intensity exercise is a good alternative for improving age-induced changes in balance, while beneficial effects on gait and spinal cord oxidative biomarkers cannot be ruled out because of the small number of rats investigated (n=5 or 6/group).

Alterations in hippocampal myelin and oligodendrocyte precursor cells during epileptogenesis

Recent reports have described damage to myelinated fibers in the central nervous system (CNS) in patients with temporal lobe epilepsy (TLE) and animal models. However, only limited data are available on the dynamic changes that occur in myelinated fibers, oligodendrocytes (which are myelin-forming cells), and oligodendrocyte precursor cells (OPCs), which are a reservoir of new oligodendrocytes, in the hippocampus throughout epileptogenesis. The current study was designed to examine this issue using a rat model of lithium-pilocarpine-induced epilepsy. Electroencephalography (EEG), immunofluorescence, and Western blot analysis showed that the loss of myelin and oligodendrocytes in the rat hippocampus began during the acute stage of epileptogenesis, and the severity of this loss increased throughout epileptogenesis. Accompanying this loss of myelin and oligodendrocytes, OPCs in the rat hippocampus became activated and their populations increased during several phases of epileptogenesis (the acute, latent and chronic phases). The transcription factors olig1 and olig2, which play crucial roles in regulating OPC proliferation, differentiation and remyelination, were up-regulated during the early phases (the acute and latent phases) followed by a sharp decline in their expression during the chronic and late chronic phases. This study is the first to confirm the loss of myelin and oligodendrocytes during lithium-pilocarpine-induced epileptogenesis accompanied by a transient increase in the number of OPCs. Prevention of the loss of myelin and oligodendrocytes may provide a novel treatment strategy for epilepsy.

Proof-of-concept randomized controlled trial of pregnenolone in schizophrenia

RATIONALE

Preclinical and clinical data suggest that pregnenolone may be a promising therapeutic in schizophrenia. Pregnenolone is neuroprotective and enhances learning and memory, myelination, and microtubule polymerization. Treatment with pregnenolone elevates allopregnanolone (a neurosteroid that enhances GABAA receptor responses) and pregnenolone sulfate (a positive NMDA receptor modulator). Pregnenolone could thus potentially mitigate GABA dysregulation and/or NMDA receptor hypofunction in schizophrenia via metabolism to other neurosteroids.

OBJECTIVE

The objective of this study is to conduct a randomized controlled trial of adjunctive pregnenolone in schizophrenia.

METHODS

Following a placebo lead-in, 120 participants were randomized to pregnenolone or placebo for 8 weeks (Institute for Mental Health, Singapore). Primary endpoints were changes in MATRICS Consensus Cognitive Battery (MCCB) composite scores (cognitive symptoms), UCSD Performance-based Skills Assessment-Brief (UPSA-B) composite scores (functional capacity), and Scale for Assessment of Negative Symptoms (SANS) total scores (negative symptoms). A modified intent-to-treat analysis approach was utilized.

RESULTS

No significant changes compared to placebo were demonstrated in composite MCCB scores. In contrast, participants randomized to pregnenolone (n = 56) demonstrated greater improvements in functional capacity (UPSA-B composite changes) compared to placebo (n = 55), p = 0.03. Pregnenolone was also superior to placebo in the communication subscale of the UPSA-B (p < 0.001). Serum pregnenolone changes post-treatment were correlated with UPSA-B composite score changes in females (r s = 0.497, p < 0.042, n = 17) but not in males. Mean total SANS scores were very low at baseline and did not improve further post-treatment. Pregnenolone was well-tolerated.

CONCLUSIONS

Pregnenolone improved functional capacity in participants with schizophrenia, but did not improve cognitive symptoms over an 8-week treatment period. Neurosteroid changes correlated with functional improvements in female participants. Neurosteroid interventions may exhibit promise as new therapeutic leads for schizophrenia.

Altered hippocampal myelinated fiber integrity in a lithium-pilocarpine model of temporal lobe epilepsy: a histopathological and stereological investigation

The damage of white matter, primarily myelinated fibers, in the central nervous system (CNS) of temporal lobe epilepsy (TLE) patients has been recently reported. However, limited data exist addressing the types of changes that occur to myelinated fibers inside the hippocampus as a result of TLE. The current study was designed to examine this issue in a lithium-pilocarpine rat model. Investigated by electroencephalography (EEG), Gallyas silver staining, immunohistochemistry, western blotting, transmission electron microscopy, and stereological methods, the results showed that hippocampal myelinated fibers of the epilepsy group were degenerated with significantly less myelin basic protein (MBP) expression relative to those of control group rats. Stereological analysis revealed that the total volumes of hippocampal formation, myelinated fibers, and myelin sheaths in the hippocampus of epilepsy group rats were decreased by 20.43%, 49.16%, and 52.60%, respectively. In addition, epilepsy group rats showed significantly greater mean diameters of myelinated fibers and axons, whereas the mean thickness of myelin sheaths was less, especially for small axons with diameters from 0.1 to 0.8µm, compared to control group rats. Finally, the total length of the myelinated fibers in the hippocampus of epilepsy group rats was significantly decreased by 56.92%, compared to that of the control group, with the decreased length most prominent for myelinated fibers with diameters from 0.4 to 0.8µm. This study is the first to provide experimental evidence that the integrity of hippocampal myelinated fibers is negatively affected by inducing epileptic seizures with pilocarpine, which may contribute to the abnormal propagation of epileptic discharge.

Remyelination - An effective means of neuroprotection

Remyelination following central nervous system (CNS) demyelination restores rapid saltatory conduction of action potentials and contributes to the maintenance of axonal integrity. This robust regenerative phenomenon stands in contrast to the limited repair capacity that is characteristic of CNS neuronal injury. However, despite its efficiency in experimental models and some clinical diseases, remyelination failure becomes an increasingly pronounced feature of the pathology of chronic multiple sclerosis (MS) lesions. Chronic demyelination predisposes axons to atrophy, an irreversible event that is a major pathological correlate of progressive functional decline. This has created a compelling case for developing therapies that promote remyelination: evidence from experimental animal models suggests that hormones may have a beneficial role to play in this regard.

DTI abnormalities in anterior corpus callosum of rats with spike-wave epilepsy

OBJECTIVE

Absence epilepsy is a common seizure disorder in children which can produce chronic psychosocial sequelae. Human patients and rat absence models show bilateral spike-wave discharges (SWD) in cortical regions. We employed diffusion tensor imaging (DTI) in rat absence models to detect abnormalities in white matter pathways connecting regions of seizure activity.

METHODS

We studied Wistar albino Glaxo rats of Rijswijk (WAG/Rij), genetic absence epilepsy rats of Strasbourg (GAERS), and corresponding nonepileptic control strains. Ex vivo DTI was performed at 9.4 T with diffusion gradients applied in 16 orientations. We compared fractional anisotropy (FA), perpendicular (lambda(perpendicular)) and parallel (lambda(||)) diffusivity between groups using t-maps and region of interest (ROI) measurements.

RESULTS

Adult epileptic WAG/Rij rats exhibited a localized decrease in FA in the anterior corpus callosum. This area was confirmed by tractography to interconnect somatosensory cortex regions most intensely involved in seizures. This FA decrease was not present in young WAG/Rij rats before onset of SWD. GAERS, which have more severe SWD than WAG/Rij, exhibited even more pronounced callosal FA decreases. Reduced FA in the epileptic animals originated from an increased lambda(perpendicular) with no significant changes in lambda(||).

INTERPRETATION

Reduced FA with increased lambda(perpendicular) suggests that chronic seizures cause reduction in myelin or decreased axon fiber density in white matter pathways connecting regions of seizure activity. These DTI abnormalities may improve the understanding of chronic neurological difficulties in children suffering with absence epilepsy, and may also serve as a noninvasive biomarker for monitoring beneficial effects of treatment.

Epileptic seizures and hippocampal damage after cuprizone-induced demyelination in C57BL/6 mice

Epileptic seizures are known to occur in different animal models of demyelination and have also been described in demyelinating diseases of the central nervous system (CNS) such as multiple sclerosis. How myelin deficiency might cause seizures is unknown, but may involve axonal pathology and resultant alterations in neuronal excitability. The cause of seizures occurring in rodent demyelination models is unknown. In the present study, we used EEG/video monitoring to record seizures occurring during chronic demyelination of C57BL/6 mice fed for 12 weeks with 0.2% cuprizone. Furthermore, in the search for a morphological correlate of the seizures, the hippocampal formation was examined histologically. Epileptiform spikes resembling interictal spikes known from chronic epilepsy were recorded in all cuprizone-treated mice, but not in controls. Most cuprizone-treated animals exhibited generalized tonic-clonic seizures upon stress-inducing stimuli. In addition to the known demyelination of the corpus callosum, massive demyelination was found in the hippocampal formation. This was associated with neuronal alterations, including a loss of neurons in the hilus of the dentate gyrus. In view of the role of the dentate gyrus in epileptogenesis, demyelination leading to axonal pathology and thus neuronal damage as observed in the hilus may be causally involved in the paroxysmal alterations observed after prolonged treatment with cuprizone. The present data suggest a potential role of the hippocampal formation for seizures occurring as a consequence of neuronal damage secondary to CNS demyelination.

Neuroactive steroids are altered in schizophrenia and bipolar disorder: relevance to pathophysiology and therapeutics

Evidence suggests that neuroactive steroids may be candidate modulators of schizophrenia pathophysiology and therapeutics. We therefore investigated neuroactive steroid levels in post-mortem brain tissue from subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects to determine if neuroactive steroids are altered in these disorders. Posterior cingulate and parietal cortex tissue from the Stanley Foundation Neuropathology Consortium collection was analyzed for neuroactive steroids by negative ion chemical ionization gas chromatography/mass spectrometry preceded by high-performance liquid chromatography. Subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects were group matched for age, sex, ethnicity, brain pH, and post-mortem interval (n = 14-15 per group, 59-60 subjects total). Statistical analyses were performed by ANOVA with post-hoc Dunnett tests on log transformed neuroactive steroid levels. Pregnenolone and allopregnanolone were present in human post-mortem brain tissue at considerably higher concentrations than typically observed in serum or plasma. Pregnenolone and dehydroepiandrosterone levels were higher in subjects with schizophrenia and bipolar disorder compared to control subjects in both posterior cingulate and parietal cortex. Allopregnanolone levels tended to be decreased in parietal cortex in subjects with schizophrenia compared to control subjects. Neuroactive steroids are present in human post-mortem brain tissue at physiologically relevant concentrations and altered in subjects with schizophrenia and bipolar disorder. A number of neuroactive steroids act at inhibitory GABA(A) and excitatory NMDA receptors and demonstrate neuroprotective and neurotrophic effects. Neuroactive steroids may therefore be candidate modulators of the pathophysiology of schizophrenia and bipolar disorder, and relevant to the treatment of these disorders.

An evaluation of the use of seizure prone rats when investigating intermediate stage sleep

A body of literature is developing which identifies an additional stage of sleep in rats, cats and mice. Intermediate stage (IS) sleep is a measurable sleep stage that is maintained by the hyperpolarization of GABA(A) containing thalamocortical neurons. The present study attempts to clarify inconsistencies within the sleep spindle literature. Most notably, inconsistencies between those that study sleep spindles in the rat outside and within the context of IS sleep. Ten male taiep rats weighing from 400 g to 600 g, and 9-12 months of age, were used in this study. The animals were given a one-time, .9 mg/kg dose of the benzodiazepine clonazepam. The control group had more seizure activity (mean = 13.4) than the treatment group (mean = 5.2, t(1-18) = 8.859, p < .001), and had a lower number of sleep spindles (mean=10.3) than the treatment group (mean = 13.3, t(1-18) = -3.4, p < .001). In addition, spectral analysis of sleep spindles during IS and seizure activity revealed that sleep spindles are within the frequency band of 8-11Hz, while seizure activity is within the 4-7 Hz range. This data supports the hypotheses that sleep spindles are distinguishable from seizure activity.