The role of endogenous opioids in the baroreflex dysfunction of dialysis patients.

We studied the effect of the opiate antagonist naloxone on the response to Valsalva manoeuvre in nine dialysis patients, in six diabetics with normal renal function whose response to Valsalva manoeuvre was similar to that of dialysis patients and in eight healthy subjects. Naloxone caused a progressive increase in the subnormal Valsalva ratio in dialysis patients but it did not cause any change in diabetics nor in healthy subjects. The increase in Valsalva ratio observed in dialysis patients was due to restoration of the parasympathetically mediated reflex bradycardia of the release phase of the manoeuvre. Endogenous opioids may be responsible for the baroreflex dysfunction of dialysis patients.