Blood pressure in rats selectively bred for their resistance to decompression sickness.

Introduction: Susceptibility to decompression sickness (DCS) is characterised by a wide inter-individual variability whose origins are still poorly understood. This hampers reliable prediction of DCS by decompression algorithms. We previously selectively bred rats with a 3-fold greater resistance to DCS than standard rats. Based on its previously reported relation with decompression outcomes, we assessed whether modification in vascular function is associated with resistance to DCS.

Methods: The arterial pressure response to intravenous administration of acetylcholine (ACh, 5 μg.kg^-1) and adrenaline (5 and 10 μg.kg^-1) was compared in anaesthetised DCS-resistant rats (seven females, seven males) and standard Wistar rats (seven females, 10 males) aged 14-15 weeks. None of these rats had previously undergone hyperbaric exposure.

Results: There was a non-significant tendency for a lower diastolic (DBP) and mean blood pressure (MBP) in DCS-resistant rats. After ACh administration, MBP was significantly lower in resistant rats, for both males (P = 0.007) and females (P = 0.034). After administration of adrenaline 10 μg.kg^-1, DCS-resistant rats exhibited lower maximal DBP (P = 0.016) and MBP (P = 0.038). Systolic and pulse blood pressure changes did not differ between groups in any of the experiments.

Conclusions: Resistance to DCS in rats is associated to a trend towards a lower vascular tone but not blood pressure reactivity. Whether these differences are a component of the susceptibility to DCS remains to be confirmed.