The nucleus locus coeruleus/subcoeruleus affects the defensive-like, immobile posture following an air-puff startle reaction in the rat.
The air-puff startle is an example of a simple behavior in mammals. Following the startle reaction, rats assume a defensive-like, immobile posture (DIP) of approximately 2-5 s in length. The aim of the present study was to examine the effect of bilateral lesions of the nucleus locus coeruleus/subcoeruleus (LC/SC) on the DIP. Using male Sprague-Dawley rats, the DIP period in the air-puff startle was measured with a digital stop watch. The DIP period was defined as the time between the application of the air-puff stimuli and the first motion after the startle reaction. For air-puff stimulation (14.4 psi in strength, 0.1 s in duration), compressed house air was presented as a transient through a vinyl tube suspended 2.5 cm above the rat's head. Two weeks before the experiment, the rats received bilateral injections of 6 microg of the neurotoxin 6-hydroxydopamine to specifically lesion noradrenaline-containing neurons of the LC/SC. In the sham-lesioned rats (n=8), the DIP period did not significantly alter compared with that before operation. In contrast, in the LC/SC-lesioned rats (n=9), the DIP period significantly reduced to 78% of the values before lesions. The results suggest that the LC/SC is involved in the development of the DIP. We speculate that the DIP period is an attentional state and vigilance condition because LC/SC neurons have been implicated in the regulation of the attentional state and vigilance.
Tsuruoka
M
M
Department of Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan. masa@dent.showa-u.ac.jp
Tamaki
J
J
Maeda
M
M
Hayashi
B
B
Inoue
T
T
D000818:Animals; D008125:Locus Coeruleus / Q000502:physiology*; D008297:Male; D011187:Posture; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle