The relationship between locomotion and heat tolerance in heat exposed rats.
Low spontaneous locomotor activity (SA) represents a thermoregulatory behaviour that aims at improving heat tolerance. However, high SA is observed during heat exposure. We hypothesized that high SA could be associated to brain dysfunction. Eighty male Sprague-Dawley rats were heat exposed for 90-min under a continuous assessment of SA and abdominal temperature (T(abd)) using telemetry. The time course analysis showed two SA peaks. The first one was related to exposure to novel environment, the second to heat. The maximal SA level reached in the second peak served to distribute the rats into three groups (LOW, MED and HIGH). In each SA pattern group, heat tolerance was estimated from T(abd) values. At the end of heat exposure, frontal cortex activation was assessed using c-fos, Hsp70 and IkappaBalpha mRNA expressions. The LOW rats exhibited the lowest T(abd), a slight increase in c-fos and Hsp70 mRNA expressions and a robust increase in IkappaBalpha mRNA expression. The HIGH rats exhibited the highest T(abd) and a robust increase in c-fos and Hsp70 mRNA expressions without any change in IkappaBalpha mRNA expression. The c-fos and Hsp70 mRNA expressions were positively correlated to the highest SA levels occurring 45 min before sacrifice, suggesting that high SA and frontal cortex activation are related. In conclusion, high SA is associated to decreased heat tolerance and frontal cortex activation. It may represent a marker of inadequate stress reaction.
Michel
Virginie
V
Département des Facteurs Humains, Pôle de neurophysiologie du stress, Institut de Recherche Biomédicale des Armées, Antenne de La Tronche, Centre de Recherches du Service de Santé des Armées, La Tronche, France. vmichel@crssa.net
Peinnequin
André
A
Alonso
Antonia
A
Fidier
Nadine
N
Maury
Renaud
R
Drouet
Jean-Baptiste
JB
Buguet
Alain
A
Cespuglio
Raymond
R
Canini
Frédéric
F
D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D005625:Frontal Lobe / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology*; D018709:Statistics, Nonparametric; D013312:Stress, Physiological
D018840:HSP70 Heat-Shock Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger