The International Journal of Neuropsychopharmacology

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The International Journal of Neuropsychopharmacology (2009), 12:95-107 Cambridge University Press
Copyright © 2008 CINP
doi:10.1017/S1461145708009140

Research Article

Chronic cold stress increases excitatory effects of norepinephrine on spontaneous and evoked activity of basolateral amygdala neurons


Deanne M. Buffalaria1 and Anthony A. Gracea1 c1

a1 Departments of Neuroscience, Psychiatry and Psychology, University of Pittsburgh, Pittsburgh PA, USA
Article author query
buffalari dm [PubMed]  [Google Scholar]
grace aa [PubMed]  [Google Scholar]

Abstract

Neurons of the amygdala respond to a variety of stressors. The basolateral amygdala (BLA) receives dense norepinephrine (NE) innervation from the locus coeruleus, and stressful and conditioned stimuli cause increases in NE levels within the BLA. Furthermore, chronic stress exposure leads to sensitization of the stress response. The actions of NE in different structures involved in the stress circuit have been shown to play a role in this sensitization response. Here, we examine how chronic cold stress alters NE modulation of spontaneous and evoked activity in the BLA. In controls, NE inhibited spontaneous firing in the majority of BLA neurons, with some neurons showing excitation at lower doses and inhibition at higher doses of NE. NE also decreased the responsiveness of these neurons to electrical stimulation of the entorhinal and sensory association cortices. After chronic cold exposure, NE caused increases in spontaneous activity in a larger proportion of BLA neurons than in controls, and now produced a facilitation of responses evoked by stimulation of entorhinal and sensory association cortical inputs. These studies show that chronic cold exposure leads to an increase in the excitatory effects of NE on BLA neuronal activity, and suggest a mechanism by which organisms may display an enhancement of hormonal, autonomic, and behavioural responses to acute stressful stimuli after chronic stress exposure.

(Received January 30 2008)

(Reviewed March 20 2008)

(Revised May 21 2008)

(Accepted June 13 2008)

(Online publication July 23 2008)

Key Words:Amygdala; cold; locus coeruleus; norepinephrine; sensitization; stress

Correspondence:

c1 Address for correspondence: Dr A. A. Grace, A210 Langley Hall, Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA. Tel.: 412-624-4609 Fax: 412-624-9198 E-mail: graceaa@pitt.edu