Cardiovascular and behavioural responses to psychological stress in spontaneously hypertensive rats: effect of treatment with DSP-4.
We used a model of psychological stress combining exposure to an open-field novel environment, radio-telemetric measurement of blood pressure and heart rate, and behavioural tracking analysis of behavioural parameters. All rats showed significant increases in blood pressure and heart rate for the duration of open-field exposure, with spontaneously hypertensive rats (SHR) showing markedly greater pressor responses and tachycardia when compared to either Wistar-Kyoto (WKY) or Sprague-Dawley rats (SD rats). Behavioural responses in the open-field were unrelated to the magnitude of cardiovascular responses. Open-field exposure on 4 consecutive days induced similar pressor responses and tachycardia on each day. By contrast, behavioural responses were reduced from the second day of open-field exposure. Treatment of SHR and WKY rats with DSP-4, to deplete central noradrenaline levels, did not affect cardiovascular responses in SHR, whereas WKY rats showed a trend towards inhibition. However, in WKY rats, but not SHR, DSP-4 treatment caused a marked reduction in behavioural activity in the open-field. In conclusion, these data show that: (1) SHR display marked cardiovascular hyperreactivity to psychological open-field stress when compared to two normotensive rat strains; (2) unlike behavioural responses, cardiovascular stress responses do not habituate upon repeated stress exposure; and (3) noradrenergic projections from the locus coeruleus do not appear to play a major role in cardiovascular stress responses in SHR or WKY rats, although they may be involved in behavioural responses in WKY rats.
van den Buuse
M
M
Baker Medical Research Institute, Vic., Prahran, Australia. m.vandenbuuse@papyrus.mhri.edu.au
Lambert
G
G
Fluttert
M
M
Eikelis
N
N
D018663:Adrenergic Agents / Q000494:pharmacology*; D000818:Animals; D001143:Arousal / Q000187:drug effects / Q000502:physiology*; D001596:Benzylamines / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013315:Stress, Psychological / Q000150:complications* / Q000503:physiopathology
D018663:Adrenergic Agents; D001596:Benzylamines; C012102:DSP 4; D009638:Norepinephrine