CRH Enhances Retention of a Spatial Memory

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Neurobiol Learn Mem. 2008 May;89(4):370-8. Epub 2007 Dec 20.

Post-training administration of corticotropin-releasing hormone (CRH) enhances retention of a spatial memory through a noradrenergic mechanism in male rats.

Row BW, Dohanich GP.
Department of Pediatrics, Kosair Children's Hospital Research Institute, University of Louisville, Louisville, KY 40202, USA.
Hormones released in response to stress play important roles in cognition. In the present study, the effects of the stress peptide, corticotropin-releasing hormone (CRH), on spatial reference memory were assessed following post-training administration. Adult Long-Evans male rats were trained for 6 days on a standard water maze task of reference memory in which animals must learn and remember the fixed location of a hidden, submerged platform. Each day, immediately following three training trials, rats received bilateral infusions of CRH into the lateral ventricles over a range of doses (0.1, 0.33, 1.0, 3.3 microg) or a vehicle solution. Post-training infusions of CRH improved retention as indicated by significantly shorter latencies and path lengths to locate the hidden platform on the first training (retention) trial of days 2 and 3. Additionally, post-training administration of CRH increased spatial bias during probe trials as measured by proximity to the platform location. CRH did not enhance performance on retention or probe trials when administered 2h after daily training indicating that CRH facilitated consolidation specifically. The effects of CRH were attenuated by intraventricular co-administration of the beta-adrenergic antagonist, propanolol, at bilateral doses that had no effect on retention alone (0.1, 1.0 microg). Results indicate that post-training administration of CRH enhanced spatial memory as measured in a water maze, and this effect was mediated, at least partly, by a noradrenergic mechanism.
PMID: 18086539 [PubMed - indexed for MEDLINE]
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http://www.ncbi.nlm.nih.gov/pubmed/18086539

Norepinephrine

From Wikipedia, the free encyclopedia

Noradrenaline (BAN) (abbreviated NA or NAd) or norepinephrine (INN) (abbreviated norepi or NE) is a catecholamine with dual roles as a hormone and a neurotransmitter.[2]

As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled. Along with epinephrine, norepinephrine also underlies the fight-or-flight response, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing blood flow to skeletal muscle.
However, when norepinephrine acts as a drug it will increase blood pressure by its prominent increasing effects on the vascular tone from α-adrenergic receptor activation. The resulting increase in vascular resistance triggers a compensatory reflex that overcomes its direct stimulatory effects on the heart, called the baroreceptor reflex, which results in a drop in heart rate called reflex bradycardia.
Norepinephrine is synthesized from dopamine by dopamine β-hydroxylase.[3] It is released from the adrenal medulla into the blood as a hormone, and is also a neurotransmitter in the central nervous system and sympathetic nervous system where it is released from noradrenergic neurons. The actions of norepinephrine are carried out via the binding to adrenergic receptors.

SEE MORE! at:

http://en.wikipedia.org/wiki/Norepinephrine

SEE ALSO:

Dopamine
http://en.wikipedia.org/wiki/Dopamine

Prolactin
http://en.wikipedia.org/wiki/Prolactin


Copyright © 1999 Elsevier Science Inc. All rights reserved.
Original Articles

Changes in hippocampal theta following intrahippocampal corticotropin-releasing hormone (CRH) infusions in the rat


Rudie Kortekaas, , a, Brenda Costalla and James W. Smythea
a Department of Pharmacology, University of Bradford, Bradford, UK

Received 7 October 1998;
revised 2 February 1999;
accepted 2 February 1999.
Available online 1 June 1999.

Abstract

Hippocampal theta activity is a large amplitude, sinusoidal wave that occurs during attentive immobility and exploratory behaviour in the rat, and it is thought to be involved in memory formation.

Recent reports suggest that corticotropin-releasing hormone (CRH) has pro-mnemonic effects in rodents.

(A mnemonic device (pronounced /nɨˈmɒnɨk/[1]) is a mind memory and/or learning aid. Commonly, mnemonics are verbal—such as a very short poem or a special word used to help a person remember something - wikipedia)

Because memory-enhancing substances/manipulations generally alter either theta frequencies or amplitudes, these variables were monitored in urethane-anaesthetised rats following intra-hippocampal infusions of CRH.

Adult male, Lister hooded rats were implanted with a hippocampal recording electrode and a guide cannula, both aimed at the dentate gyrus.

When CRH was infused into the hippocampus, the main change in the hippocampal EEG was a slow onset increase in the amplitude of spontaneous theta and, paradoxically, a significant decrease in the amount of time spent displaying theta.

These data suggest that CRH has the ability to modulate ongoing hippocampal theta, but, considering the slow effect, the involvement of hippocampal CRH receptors is suspect. Regardless of locus, the described electrophysiological changes suggest that hippocampal cholinergic systems may play a role in the memory-enhancing effects of CRH.

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