Behavioral and Autonomic Responses to Acute Restraint Stress Are Segregated within the Lateral Septal Area of Rats

Daniel G Reis,América A Scopinho,Leonardo B M Resstel,Fernando M A Corrêa,Francisco S Guimarães,Jerson Laks

doi:10.1371/journal.pone.0023171

Abstract

BackgroundThe Lateral Septal Area (LSA) is involved with autonomic and behavior responses associated to stress. In rats, acute restraint (RS) is an unavoidable stress situation that causes autonomic (body temperature, mean arterial pressure (MAP) and heart rate (HR) increases) and behavioral (increased anxiety-like behavior) changes in rats. The LSA is one of several brain regions that have been involved in stress responses. The aim of the present study was to investigate if the neurotransmission blockade in the LSA would interfere in the autonomic and behavioral changes induced by RS.Methodology/Principal FindingsMale Wistar rats with bilateral cannulae aimed at the LSA, an intra-abdominal datalogger (for recording internal body temperature), and an implanted catheter into the femoral artery (for recording and cardiovascular parameters) were used. They received bilateral microinjections of the non-selective synapse blocker cobalt chloride (CoCl2, 1 mM/ 100 nL) or vehicle 10 min before RS session. The tail temperature was measured by an infrared thermal imager during the session. Twenty-four h after the RS session the rats were tested in the elevated plus maze (EPM).Conclusions/SignificanceInhibition of LSA neurotransmission reduced the MAP and HR increases observed during RS. However, no changes were observed in the decrease in skin temperature and increase in internal body temperature observed during this period. Also, LSA inhibition did not change the anxiogenic effect induced by RS observed 24 h later in the EPM. The present results suggest that LSA neurotransmission is involved in the cardiovascular but not the temperature and behavioral changes induced by restraint stress.

Highlights

Stress situations are well-known to trigger autonomic and behavior responses that are accompanied by activation of several brain structures [1]
The present results suggest that Lateral Septal Area (LSA) neurotransmission is involved in the cardiovascular but not the temperature and behavioral changes induced by restraint stress
The injection of CoCl2 into the LSA significantly attenuated the increases in both (MAP: F1,360 = 93, P,0.001) and (HR: F1,360 = 126, P,0.001, Figure 2) observed during restraint

Summary

Introduction

Stress situations are well-known to trigger autonomic and behavior responses that are accompanied by activation of several brain structures [1]. The autonomic responses includes mean arterial pressure (MAP) and heart rate (HR) increases [7,16,17,18,19,20], skeletal muscle vasodilatation and cutaneous vasoconstriction, which are accompanied by a rapid skin temperature drop and followed by body temperature increases [21,22] In addition to those autonomic responses, animals submitted to restraint present behavioral changes such as reduced exploratory activity in an open field [23,24,25], increased immobility in a forced swimming test [26] and reduced exploration of the open arms of an elevated plusmaze (EPM) 24 h after the stress session [27,28].

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