[Hyperalgesic effect of subarachnoid administration of phentolamine in mice].

Background And Objectives: Painful phenomenon is one of the most important and complex experiences. Phentolamine is a non-selective alpha-adrenergic antagonist. The objective of this study was to compare the effect of increasing doses of phentolamine into subarachnoid space in rats in the modulation of painful phenomenon.

Subarachnoid serotonergic and noradrenergic antagonists increase the pain response in rats.

Background And Objectives: There is evidence that the passage of nociceptive information through the posterior horn of the spinal cord (PHSC) on its way to rostral levels of the central nervous system undergoes profound excitatory and inhibitory influences. The objective of the present study was to compare the effects of the subarachnoid administration of methysergide, phentolamine, and phentolamine associated with methysergide on phases I, intermediate, and II of the modified formalin test in rats.

Methods: Twenty-eight male Wistar rats distributed randomly in four groups (n=7) to received subarachnoid saline solution (GC), phentolamine (GF), methysergide (GM), or phentolamine associated with methysergide (GFM).