Exercise, Stress Resilience, and Locus Ceruleus Galanin

 reposted from SfN

Full paper

https://www.jneurosci.org/content/40/39/7464

Exercise, Stress Resilience, and Locus Ceruleus Galanin

Rachel P. Tillage, Genevieve E. Wilson, L. Cameron Liles, Philip V. Holmes, and David Weinshenker

(see pages 7464–7474)

Regular exercise improves mood and cognition, reduces stress, and increases resilience to subsequent stressors. These effects are mediated by multiple signaling pathways that affect synaptic plsticity and neuronal health in several brain areas. Much evidence suggests that exercise promotes stress resilience by increasing production of the neuropeptide galanin in the locus ceruleus, a structure that drives stress responses by releasing norepinephrine throughout the brain. Galanin is expressed in most locus ceruleus neurons, and it can inhibit spontaneous spiking in noradrenergic neurons. Notably, chronic exercise increases galanin levels in the locus ceruleus of rats, and intracerebroventricular infusion of a galanin antagonist blocks the ability of exercise to increase stress resilience. Moreover, intracerebroventricular infusion of galanin increases stress resilience in rats. Because intracerebroventricular treatments can affect galanin signaling in many brain areas, including hypothalamic nuclei involved in stress responses, Tillage et al. examined the effects of overexpressing galanin selectively in noradrenergic neurons in mice.

The authors first confirmed that 3 week access to a running wheel increased exercise, galanin expression, and stress resilience in mice. Indeed, mice ran 10–16 km/d by the third week of wheel access, and galanin expression in the locus ceruleus of these mice was higher than in sedentary controls. Notably, locus ceruleus galanin levels were correlated with the amount of running and with levels of anxiety-like behavior after footshock stress. In particular, whereas stress caused sedentary mice to spend less time in the open arms of an elevated zero maze the next day, it had no effect on mice that had exercised. Importantly, overexpressing galanin in noradrenergic neurons replicated the effects of exercise—preventing stress-induced increases in anxiety-like behavior in the elevated zero maze—but had no effect on baseline behavior or on acute responses to footshock. Finally, optogenetic activation of the locus ceruleus replicated the effects of footshock stress, and overexpressing galanin in the locus ceruleus blocked this effect.

These data strengthen the hypothesis that increases in galanin expression in the locus ceruleus mediate the effect of exercise on stress resilience. Whether this effect stems from suppression of noradrenergic neuronal activity, effects on locus ceruleus target regions, or both should be examined in future studies.

Footnotes

• This Week in The Journal was written by Teresa Esch, Ph.D.

reposted from

Structural Plasticity within the Barrel Cortex during Initial Phases of Whisker-Dependent Learning

1. Sandra J. Kuhlman¹,²,*, 
2. Daniel H. O'Connor¹,*, 
3. Kevin Fox¹,³, and 
4. Karel Svoboda¹

+Show Affiliations

1. Author contributions: S.J.K., D.H.O., K.F., and K.S. designed research; S.J.K. performed research; S.J.K. analyzed data; S.J.K., D.H.O., K.F., and K.S. wrote the paper.

1. The Journal of Neuroscience, 23 April 2014, 34(17): 6078-6083; doi: 10.1523/JNEUROSCI.4919-12.2014

• Abstract
• Full Text
• Full Text (PDF)

Abstract

We report learning-related structural plasticity in layer 1 branches of pyramidal neurons in the barrel cortex, a known site of sensorimotor integration. In mice learning an active, whisker-dependent object localization task, layer 2/3 neurons showed enhanced spine growth during initial skill acquisition that both preceded and predicted expert performance. Preexisting spines were stabilized and new persistent spines were formed. These findings suggest rapid changes in connectivity between motor centers and sensory cortex guide subsequent sensorimotor learning.

• barrel cortex
 
• object localization
 
• perceptual learning
 
• plasticity

reposted from

PUBLIC RELEASE DATE:

14-Apr-2014

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Contact: Latarsha Gatlin
lgatlin1@jhu.edu
443-997-9909
Johns Hopkins University 

Neuroscientists: Brain activity may mark the beginning of memories

By tracking brain activity when an animal stops to look around its environment, neuroscientists at the Johns Hopkins University believe they can mark the birth of a memory.

Using lab rats on a circular track, James Knierim, professor of neuroscience in the Zanvyl Krieger Mind/Brain Institute at Johns Hopkins, and a team of brain scientists noticed that the rats frequently paused to inspect their environment with head movements as they ran. The scientists found that this behavior activated a place cell in their brain, which helps the animal construct a cognitive map, a pattern of activity in the brain that reflects the animal's internal representation of its environment.

In a paper recently published in the journal Nature Neuroscience, the researchers state that when the rodents passed that same area of the track seconds later, place cells fired again, a neural acknowledgement that the moment has imprinted itself in the brain's cognitive map in the hippocampus.

The hippocampus is the brain's warehouse for long- and short-term processing of episodic memories, such as memories of a specific experience like a trip to Maine or a recent dinner. What no one knew was what happens in the hippocampus the moment an experience imprints itself as a memory.

"This is like seeing the brain form memory traces in real time," said Knierim, senior author of the research. "Seeing for the first time the brain creating a spatial firing field tied to a specific behavioral experience suggests that the map can be updated rapidly and robustly to lay down a memory of that experience."

A place cell is a type of neuron within the hippocampus that becomes active when an animal or human enters a particular place in its environment. The activation of the cells

helps create a spatial framework much like a map, that allows humans and animals to know where they are in any given location. Place cells can also act like neural flags that "mark" an experience on the map, like a pin that you drop on Google maps to mark the location of a restaurant.

"We believe that the spatial coordinates of the map are delivered to the hippocampus by one brain pathway, and the information about the things that populate the map, like the restaurant, are delivered by a separate pathway," Knierim said. "When you experience a new item in the environment, the hippocampus combines these inputs to create a new spatial marker of that experience."

In the experiments, researchers placed tiny wires in the brains of the rats to monitor when and where brain activity increased as they moved along the track in search of chocolate rewards. About every seven seconds, the rats stopped moving forward and turned their heads to the perimeter of the room as they investigated the different landmarks, behavior called "head-scanning."

"We found that many cells that were previously silent would suddenly start firing during a specific head-scanning event," Knierim said. "On the very next lap around the track, many of these cells had a brand new place field at that exact same location and this place field remained usually for the rest of the laps. We believe that this new place field marks the site of the head scan and allows the brain to form a memory of what it was that the rat experienced during the head scan."

Knierim said the formation and stability of place fields and the newly activated place cells requires further study. The research is primarily intended to understand how memories are formed and retrieved under normal circumstances, but it could be applicable to learning more about people with brain trauma or hippocampal damage due to aging or Alzheimer's.

"There are strong indications that humans and rats share the same spatial mapping functions of the hippocampus, and that these maps are intimately related to how we organize and store our memories of prior life events," Knierim said. "Since the hippocampus and surrounding brain areas are the first parts of the brain affected in Alzheimer's, we think that these studies may lend some insight into the severe memory loss that characterizes the early stages of this disease."

###

Other authors on this research are: Joseph Monaco, a post-doctoral fellow with the Johns Hopkins Krieger Mind/Brain Institute and the Biomedical Engineering Department at the Johns Hopkins School of Medicine; Geeta Rao, a researcher at the Mind/Brain Institute; and Eric D. Roth, an assistant professor at the University of Delaware.

This research was supported by NIH grants R01 MH094146, R01 NS039456 and P01 NS038310.

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