The granule cell layer of the dentate gyrus. Image provided by Mark Maynard.

Binge drinking damages brain regions responsible for memory, decision-making, and behavioral control. After a binge, the brain begins to heal itself but not much is known about this self-repair process. In a study published in PLoS ONE, researchers used rats to find that binge drinking damages the hippocampus, and exercise reverses this damage.

The study found that excessive ethanol killed granule neurons in the dentate gyrus (DG), a part of the hippocampus, and significantly decreased the volume of the DG. Rats that exercised after binging had more DG granule neurons and a larger DG than rats that did not exercise after a binge. In fact, rats that exercised after binging had a similar number of DG neurons and a similar DG volume to that of controls, indicating that exercise almost fully reversed damaged to the DG caused by binge drinking.

“The granule cell layer of the dentate gyrus is an incredibly dense layer of mature neurons that is typically very difficult to quantify and make assessments of,” said Mark E. Maynard, a co-author of the paper. “In addition, the hippocampus itself is a very large structure relative to the rest of the rodent brain, adding to the difficulty of quantifying changes to it.”

To analyze the dentate gyrus, Mark Maynard and Dr. Leasure used an MBF system equipped with a Nikon Eclipse 80i microscope and Stereo Investigator. They used the Optical Fractionator probe in Stereo Investigator to quantify the number of granule cells in the DG and the Cavalieri probe to quantify volume of the DG.

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“Using Stereo Investigator software we were able to look at a sample of the dentate gyrus and get an accurate estimate of the number of remaining granule cells and volume of the layer itself that was sensitive, to detect changes in response to binge alcohol exposure,” said Mark Maynard.

Mark Maynard and Dr. Leasure describe the stereology study in detail in the methods section of their paper. Read it here: Maynard ME, Leasure JL (2013) Exercise Enhances Hippocampal Recovery following Binge Ethanol Exposure. PLoS ONE 8(9): e76644. doi:10.1371/ journal.pone.0076644

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The researchers used Stereo Investigator to measure the volume of the hippocampus and two of its sub-regions (CA1 and CA3) in the brains of degus that were either group-housed, or held alone for six and a half months. Using a Leica DRIV microscope equipped with a MicroFire digital camera, they analyzed cresyl-violet stained sections of the left-brain hemisphere, calculating total volume with the Cavalieri probe in Stereo Investigator. They saw one major difference: the isolated animals had a smaller CA1—part of the hippocampus involved in learning—though total hippocampal volume and CA3 volume remained unchanged.

In their paper, the scientists speculate that the decrease in CA1 volume may be due to dendrite shrinkage in pyramidal neurons or glial cell loss. Also, they associate the reduced volume with deficits in contextual fear memory—a measure of learning—that they saw during behavioral testing.

Scientists studied cresyl-violet stained sections of the left brain hemispheres of isolated and group-housed rodents. Image courtesy of the Venero Lab at The National University of Distance Education in Madrid, Spain.

When the scientists looked closer at the mechanisms behind learning and memory processes, they saw lower levels of a molecule known to regulate neuronal synaptic plasticity and contextual fear memory. Known as polysialylated neural cell adhesion molecule (PSA-NCAM), the molecule was reduced in synapses in the hippocampus of the isolated animals, according to the paper.

“In summary, this study reports that social isolation of adult female degus impairs contextual fear conditioning and reduces synaptic PSA-NCAM levels in the hippocampus. Interestingly, shrinkage of CA1, but not of CA3 or the total hippocampus, was found after long-term social isolation, an effect that may be related to the impairment we observed in contextual fear memory,” the authors say.

Pereda-Pérez, I., Popović, N., Otalora, B. B., Popović, M., Madrid, J. A., Rol, M. A., & Venero, C. (2013). Long-term social isolation in the adulthood results in CA1 shrinkage and cognitive impairment. Neurobiology of Learning and Memory.

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“Treatment options are clearly urgently required to prevent the brain damage and associated memory deficits that follow extremely premature birth,” say the authors of a study published last month in the Journal of Neuroscience.

Treatment options are limited, the authors say, because current small animal models fall short in their mimicry of the extremely premature human brain. However, the researchers from the University of Otago in New Zealand have come up with a new animal model for human extreme prematurity, which they say more closely resembles the pathological and behavioral deficits seen among this populationThe research team developed the model by exposing rats to an oxygen deficient environment at one to three days of age, a period equivalent to 24-26 weeks human gestation.

By performing behavioral assessments and a stereological analysis of several different regions of the rat brains, the scientists saw similarities in “short and long-term white matter neuropathological injury, gray matter volume loss, and long-term memory deficits” between the rats and children born extremely prematurely.

Oligodendrocytes, pictured here with a green fluorescent protein, form a myelin sheath – the insulation around axons. The extremely premature brain features a lower number of pre-oligodendrocytes, thereby decreasing myelination, a characteristic which has been associated with ADHD. Image courtesy of Wikimedia Commons.

They used the Cavalieri, optical fractionator, optical disector, and nucleator probes in Stereo Investigator to quantify different elements of brain tissue. The researchers found that, compared to controls, the hypoxic rats had a lower number of pre-oligodendrocytes at four-days-old, and at 14-days-old displayed less cerebral white matter volume and myelin, as well as less cerebral cortical and striatal gray matter volume without neuronal loss – pathological characteristics also present in the brains of humans born extremely premature.

Behavioral tests showed the mice mimicked behavioral characteristics in children and adults born extremely prematurely, displaying memory deficits and ADHD-like hyperactivity.

“This new rat model provides a clinically relevant tool to investigate numerous cellular, molecular, and therapeutic questions on brain injury attributable to extreme prematurity,” the authors say.

Oorschot, Dorothy E., Voss, Logan, Covey, Matthew V., Goddard, Liping, Huang, William, Birchall, Penny, Bilkey, David K. and Kohe, Sarah E. (2013). Spectrum of Short- and Long-Term Brain Pathology and Long-Term Behavioral Deficits in Male Repeated Hypoxic Rats Closely Resembling Human Extreme Prematurity. The Journal of Neuroscience, 33(29), 11863–11877. doi: 10.1523/jneurosci.0342-12.2013.

Image courtesy: Wikimedia Commons

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In their study, published in the Journal of Enzyme Inhibition and Medicinal Chemistry, the scientists saw a smaller region of damage in a rat model of focal cerebral ischemia, when the rats were treated with a combination of an anesthetic and a Caspase-3 inhibitor – a drug that suppresses a protein involved in brain cell death.

According to the study, Caspase inhibitors are normally injected directly into the brain, diverting the need to pass through the protective blood-brain-barrier. But the authors, relying on evidence from previous studies that describe a disruption in the blood-brain-barrier after cerebral ischemia, found that Caspase-3 inhibitors were able to reach their cerebral targets after being injected into the body. “BBB disruption allows the [intraperitoneal] administration of caspase-3 inhibitor in order to assess perinfarct tissues, circumventing the need for invasive intracranial administration,” the authors say in their paper.

The researchers neurologically evaluated the rats based on motor function at days zero, four, and fourteen post ischemia. At the two-week mark, they euthanized the animals, sectioned their brains, and used Stereo Investigator to carry out an unbiased stereological analysis of the damaged sites. They quantified damaged cells with the optical fractionator and optical disector probe and used the Cavalieri estimator to measure the volume of the damaged region.

“In the neurological score, we found that the combination of anesthetics with caspase inhibitors substantially improve neurological deficit 4 days after the insult,” the authors say in their paper. “Our results also suggest that intraperitoneal injection of caspase-3 inhibitor in combination with Isoflurane or Propofol has a significant effect in reducing the volume of the infarct, when the injury was assessed at 14 days following the insult. However, tunel-positive cells and cleaved caspase-3-positive cells numbers were significantly decreased by the anesthetic-caspase inhibitor combination or the caspase-inhibitor alone, but not by the anesthetics alone.”

[Chaparro, E., Erasso, D., Quiroga, C., Bosco, G., Parmagnani, A., Rubini, A., Mangar, D., Camporesi, E. (2012). Repetitive intraperitoneal caspase-3 inhibitor and anesthesia reduces neuronal damage. Journal of Enzyme Inhibition and Medicinal Chemistry, (00), 1-7.

Image: MRI scan of human head via iStock Photo.

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If a head gets hit hard enough, the trauma occurs instantly. Neurons die, the brain swells as microglia cells rush to the damaged area, and the protective armor known as the blood brain barrier might even rupture. But it doesn’t end there. Long term effects include cognitive impairment, loss of sensory processing, and susceptibility to neurodegenerative diseases like Alzheimer’s.

Researchers at the University of South Florida say patients suffering from chronic Traumatic Brain Injury (TBI) experience a “cascade of events” marked by long-term neuroinflammation, cell loss, and impaired cell proliferation that may manifest over time.

“While TBI is generally considered an acute injury, a chronic secondary cell death perturbation (i.e., neuroinflammation) and a diminished endogenous repair mechanism (i.e., cell proliferation) accompany the disease pathology over long-term,” the authors say in their paper published this month in PLOS ONE.

The scientists used unbiased stereology to analyze activated microglia cells, cell proliferation, and differentiation into immature neurons in several regions of the brains of rats which had experienced TBI eight weeks prior.

They used Stereo Investigator with the Cavalieri estimator probe and the optical fractionator probe to estimate the quantity and volume of stained cells in the cortex, striatum, thalamus, fornix, cerebral peduncle, and corpus callosum, as well as the subgranular zone and the subventricular zone in both hemispheres of the brain.

Figure 3 from “Hippocampal CA3 cell loss and downregulation of cell proliferation.”

Eight weeks after the TBI occurred, the researchers found an increased level of active microglia cells at the direct site of the TBI as well as surrounding regions. They also report a decrease in hippocampal neurons, and low levels of cell proliferation in the neurogenic niches.

“Our overarching theme advances the concept that a massive neuroinflammation after TBI represents a second wave of cell death that impairs the proliferative capacity of cells, and impedes the regenerative capacity of neurogenesis in chronic TBI,” the authors say in their paper.

They go on to suggest a “multi-pronged treatment targeting inflammatory and cell proliferative pathways” may help alleviate the pathological effects of chronic TBI.

Read the full paper “Long-Term Up-regulation of Inflammation and Suppression of Cell Proliferation in the Brain of Adult Rats Exposed to Traumatic Brain Injury Using the Controlled Cortical Impact Model” on PLOS ONE.

Source: Acosta S.A., Tajiri N., Shinozuka K., Ishikawa H., Grimmig B., et al. (2013). Long-Term Up-regulation of Inflammation and Suppression of Cell Proliferation in the Brain of Adult Rats Exposed to Traumatic Brain Injury Using the Controlled Cortical Impact Model. PLoS ONE 8(1): e53376. doi:10.1371/journal.pone.0053376

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