Sympathetic-adrenal medullary responses to acute stress in Dahl hypertensive (S/JR) rats.
Sympathetic-adrenal medullary responses to acute footshock stress were assessed in inbred Dahl salt-sensitive (S/JR) and salt-resistant (R/JR) rats by measuring plasma levels of norepinephrine (NE) and epinephrine (EPI). Ten-week-old S/JR and R/JR rats were surgically prepared with indwelling tail artery catheters which permitted direct measurements of mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min) and remote sampling of blood. Two days after surgery, S/JR and R/JR rats were subjected to an acute stress paradigm. Blood samples were collected before and 3 minutes after transfer of rats to a shock chamber, after 1 minute of intermittent footshock, and again 5 minutes later. S/JR rats had significantly higher resting MAP's compared to R/JR rats. In contrast, baseline heart rates were similar for rats of the two strains. Basal plasma levels of NE and EPI were also similar in S/JR and R/JR rats. Upon transfer from the home cage to a shock chamber, S/JR rats exhibited significant increases in plasma levels of both catecholamines, while R/JR rats maintained circulating levels of NE and EPI that were near baseline values. However, S/JR and R/JR rats had similar increments in plasma NE and EPI following acute footshock stress. Five minutes after footshock, levels of NE and EPI returned toward baseline values for R/JR's, but remained significantly elevated above baseline in hypertensive S/JR rats. These data suggest that S/JR rats are more responsive than R/JR controls to the mild stress of transfer, but exhibit comparable responses to the more intense stress of inescapable footshock.(ABSTRACT TRUNCATED AT 250 WORDS)
Murphy
C A
CA
Department of Psychology, University of Virginia, Charlottesville 22903.
Konarska
M
M
McCarty
R
R
D000313:Adrenal Medulla / Q000294:innervation*; D000818:Animals; D001143:Arousal / Q000502:physiology*; D001794:Blood Pressure; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate; D006973:Hypertension / Q000097:blood / Q000235:genetics*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012982:Sodium, Dietary / Q000009:adverse effects; D013564:Sympathetic Nervous System / Q000503:physiopathology*
D012982:Sodium, Dietary; D009638:Norepinephrine; D004837:Epinephrine