Differentiation of cardiac baroreflex properties by cuff and drug methods in two XXXX strains.

@entity1510 @entity1168 @entity591 @entity95
Sigmoidal mean arterial pressure (MAP)-heart rate (HR) curves were obtained in two genetically related strains of @entity95 (groups I and II). We examined vagal (V) and sympathetic (S) effects on HR using perivascular cuffs and vasoactive drugs to alter MAP, and we studied the effects of intravenous @entity1510 , which affected only I. With the cuff method, both V and S components of gain were much greater in I than in II, and @entity1510 greatly reduced the difference. With the drug method, gain was similar in I and II and unaffected by @entity1510 . With both methods, the V component of HR range between plateaus was greater in I than in II because of more pronounced @entity1168 at the lower plateau; @entity1510 eliminated the latter difference when the reflex was drug induced but not when it was cuff induced. The S component of HR range was similar in I and II; with both methods, the @entity591 plateau was reduced by @entity1510 . The cuff method alters cardiac load more than the drug method, leading to engagement of different groups of afferents for a given change in MAP (delta MAP). We have derived an input-output model, which suggests that with the drug method, gain is almost entirely determined by the input from the arterial baroreceptors, accounting for the minimal difference between I and II. With the cuff method, gain is determined by a nonlinear interaction involving the arterial and nonarterial baroreceptors, which accentuates the response. The opiate mechanism is associated with the nonarterial baroreceptor input and has amplifying properties, which account for the difference in gain between I and II. The two methods and @entity1510 provide a novel way of differentiating the effector patterns of the reflex; @entity1510 serves as a marker of activity in a particular pathway.
