We investigated the effects of shaker stress on blood pressure (BP) and heart rate (HR) short-term variability and spontaneous baroreceptor reflex (BRR) sensitivity in adult normotensive Wistar rats (WR) and borderline hypertensive rats with family history of hypertension (BHR). Experiments were performed in accordance with Directive 86/609/ECC: under xylazine/ketamine anesthesia (0.4 ml 10% ketamine IP,0.1 ml 2% xylazine IP) TA11PA-C40 DSI implants were inserted in abdominal aorta and rats were treated with metamizol (200mg IP) for pain refief. At the end of experiments rats were euthanized with bolus overdose of thiopentone sodium. Only after full recovery (10 days) rats were included in experimentation. BP was recorded 20 minutes before, during acute exposure to shaking platform at 200 cycles/min/10 minutes, and 30 minutes after. This was followed by random exposure to 5 minutes long shaking period 18 times/day/3 days (1). BP was recorded during the last exposure to stress, as well as 30 minutes after. Arterial BP was digitalized at 1000Hz. Systolic BP (SBP), diastolic BP (DBP) and HR were derived from the arterial BP as maximum, minimum and inverse of interbeat interval, respectively. Evaluation of the spontaneous BRR was performed by using the method of sequences and calculation of baroreceptor reflex sensitivity-BRS and effectiveness index-BEI (2).Time spectra were calculated on 15 overlapping 2048 point time series involving 410-s registration period (3). Spectra were analyzed in very-low-frequency (VLF:0.0195-0.195Hz), low-frequency (LF:0.195-0.8Hz) and high-frequency (HF:0.8-3Hz) band. Statistical significance was assessed with one-way ANOVA. Basal values of SBP, DBP and HR were comparable in both strains. Exposure of WR and BHR to acute shaker stress increased SBP and DBP (WR:124.5 ± 4.5 mmHg, p<0.05 and 95.3 ± 2.0 mmHg, p<0.05; BHR:149.3 ± 3.4 mmHg, p<0.01 and 109.9 ± 3.9 mmHg, p<0.05), and reduced VLF SBP and VLF DBP (WR:2.8 ± 0.7 mmHg²/Hz, p<0.05 and 1.5 ± 0.1 mmHg²/Hz, p<0.05; BHR:2.0 ± 0.3 mmHg²/Hz, p<0.05 and 2.3 ± 0.4 mmHg²/Hz, p<0.05). In HR spectra of WR, but not of BHR, LF HR (13.2 ± 0.4 bpm²/Hz, p<0.05) and HF HR (5.6 ± 0.6 bpm²/Hz, p<0.05) increased. Chronic stress increased HF SBP and HF DBP in both strains (WR:0.5 ± 0.1 mmHg²/Hz, p<0.05 and 0.4 ± 0.1 mmHg²/Hz, p<0.05; BHR: 0.5 ± 0.1 mmHg²/Hz, p<0.05 and 0.4 ± 0.1 mmHg²/Hz, p<0.05), and enhanced LF HR (5.9 ± 1.3 bpm²/Hz, p<0.05) and HF HR (2.5 ± 0.6 bpm²/Hz, p<0.05) only in WR. BRS and BEI did not change during acute and chronic exposure to stress in both strains. Spectral analysis results show that BHR exhibit reduced HR variability response to acute and chronic shaker stress in comparison to normotensive control, suggesting remodeling of cardiac regulation in absence of hypertension.