Contrasting actions of intrathecal U50,488H, @entity1286 , or [D-Pen2, D-Pen5] XXXX or intravenous U50,488H on the visceromotor response to @entity14 in the rat.

@entity10971 @entity3825 @entity14 @entity158 @entity1286
BACKGROUND: Visceral sensations are an important component of many clinical @entity158 states. It is apparent that intrathecal @entity158 relief may be more effective if appropriate combinations of drugs rather than a single agent can be used. The purpose of this study was to examine the relative contribution of opioid receptor subtypes to visceral antinociception using @entity14 as a @entity3825 model. METHODS: The minimum colorectal distending pressure necessary to evoke a visceromotor response (contraction of abdominal musculature) was determined before and after the administration of opioid agonists for the mu ( @entity1286 ), delta ([D-Pen2, D-Pen5] @entity10971 [DPDPE]), and kappa (U50,488H) opioid receptors. In addition to the three drugs administered intrathecally, U50, 488H was also administered intravenously. RESULTS: @entity1286 and DPDPE produced a reversible increase in threshold for activation of the visceromotor response (50% maximum possible effect [MPE] at intrathecal doses of 2.2 and 16.4 micrograms, respectively). The maximum intrathecal dose of U50,488H (100 micrograms) produced only a 20% MPE. Intravenous U50,488H produced a 50% MPE at a dose of 2.6 mg/kg. CONCLUSIONS: The results suggest that spinal mu- and delta- but not kappa-opioid receptors have a significant role in the modulation of visceral nociception induced by @entity14 . In addition, the results indicate that activation of nonspinal kappa receptors may mediate visceral antinociception.
