Intra-strain variations of baroreflex sensitivity in young Wistar-Kyoto rats.
OBJECTIVE
To compare baroreflex sensitivity among conscious rats of the same strain.


METHODS
Male WKY rats (eight weeks old) were studied. Cannulas were inserted into the abdominal aortic artery through the right femoral artery to measure mean arterial pressure (MAP) and heart rate (HR). Baroreflex gain was calculated as the ratio between variation of HR in function of the MAP variation (?HR/?MAP) tested with a depressor dose of sodium nitroprusside (SNP, 50 microg/kg, iv) and with a pressor dose of phenylephrine (PE, 8 microg/kg, iv). We divided the rats into four groups: 1) Low bradycardic baroreflex (LB), BG between -1 and -2 bpm/mmHg tested with PE; 2) High bradycardic baroreflex (HB), BG < -2 bpm/mmHg tested with PE; 3) Low tachycardic baroreflex (LT), BG between -1 and -2 bpm/mmHg tested with SNP and; 4) High tachycardic baroreflex (HT), BG < -2 bpm/mmHg tested with SNP. Significant differences were considered for p < 0.05.


RESULTS
Approximately 82% of the rats presented reduced bradycardic reflex while 22 showed attenuated tachycardic reflex. No alterations were noted regarding basal MAP and HR, tachycardic and bradycardic peak and HR range.


CONCLUSIONS
There was alteration in baroreflex sensitivity among rats of the same strain. Care should be taken when interpreting studies employing WKY as a control for the SHR.
Valenti
Vitor E
VE
Department of Medicine, Cardiology Division, UNIFESP, 04039-032, São Paulo, SP, Brazil. valenti@unifesp.br
Imaizumi
Caio
C
de Abreu
Luiz Carlos
LC
Colombari
Eduardo
E
Sato
Monica A
MA
Ferreira
Celso
C
D000818:Animals; D017704:Baroreflex; D001794:Blood Pressure; D006339:Heart Rate; D008297:Male; D051381:Rats; D011921:Rats, Inbred WKY; D013045:Species Specificity