Habituation and sensitization of plasma catecholamine responses to chronic intermittent stress: effects of stressor intensity.
Adult male Sprague-Dawley rats were exposed acutely (1 time for 30 minutes) or chronically (30 minutes per day for 27 days) to swim stress in water maintained at either 18 degrees C, 24 degrees C or 34 degrees C. Each rat was prepared with an indwelling tail artery catheter to allow for direct measures of mean arterial pressure (MAP, mmHg) and heart rate (HR, beats per minute) and for remote collection of blood samples before, during and after the 1st or 27th swim stress session. Blood samples were later analyzed for plasma levels of norepinephrine and epinephrine to serve as an assessment of sympathetic-adrenal medullary activity. Compared to handled controls, body weight gain was reduced significantly in rats exposed chronically to swim stress at any of the 3 temperatures. However, baseline values of MAP and HR and plasma levels of norepinephrine and epinephrine were similar in chronically stressed rats compared to their handled controls. The plasma norepinephrine response of rats exposed chronically to either 18 degrees C or 24 degrees C swim stress was significantly greater than that of matched controls stressed for the first time. In contrast, the plasma epinephrine response of chronically stressed rats from these two groups was slightly but not significantly reduced compared to matched controls. For swim stress at 34 degrees C, the plasma norepinephrine and epinephrine responses of chronically stressed rats were reduced significantly compared to controls stressed for the first time. These findings demonstrate that stressor intensity affects sensitization and habituation of plasma catecholamine responses in laboratory rats exposed to chronic intermittent stress.(ABSTRACT TRUNCATED AT 250 WORDS)
Konarska
M
M
Department of Psychology, University of Virginia, Charlottesville 22903.
Stewart
R E
RE
McCarty
R
R
D000818:Animals; D001143:Arousal / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D004837:Epinephrine / Q000097:blood*; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains
D009638:Norepinephrine; D004837:Epinephrine