Cardiorespiratory effects produced by injecting drugs that affect XXXX receptors into nuclei associated with the ventral surface of the medulla.

@entity6341 @entity1246 @entity4486 @entity1027 @entity4650 @entity468 @entity551 @entity386
It has recently been shown that @entity4650 induced stimulation of cell bodies in a circumscribed area of the rostral ventrolateral medulla (RVLM) in the cat, produced increases in arterial pressure (AP), decreases in heart rate (HR) and transient @entity386 (Gatti, Norman, DaSilva and Gillis, 1986). The purpose of the present study was to determine if this same area was sensitive to @entity1246 receptor agonists and antagonists. Injection of the @entity1246 agonist @entity6341 (200 ng), into the rostral ventrolateral medulla of @entity468 anesthetized with @entity4486 produced a precipitous and immediate fall in arterial pressure (-95 +/- 4.6) and heart rate (-31 +/- 5.9; n = 4, P less than 0.05). Maximal cardiovascular effects could only be achieved if @entity6341 was injected bilaterally. These effects of @entity6341 on arterial pressure were dose-dependent. Time-action curves for the effects of @entity6341 on arterial pressure and respiration were different. @entity551 occurred first and was followed later in time by a decrease in minute ventilation. Within 30 min all animals were apneic after the 200 ng dose. The cardiovascular effects of @entity6341 were reversed by the injection of the @entity1246 receptor antagonist @entity1027 . These data indicate that stimulation of @entity1246 receptors in the rostral ventrolateral medulla produced selective cardiovascular effects and that respiratory neurons sensitive to @entity1246 are apparently not localized with these cardiovascular neurons.
