The rat urinary bladder. A novel preparation for the investigation of central opioid activity in vivo.
A novel method, which utilized spontaneous, volume-induced contractions of the urinary bladder in the anesthetized rat, was developed to assess the central activity of substances with opioid properties. It was discovered that intracerebroventricular (i.c.v.) injections made directly into the lateral ventricle or intrathecal (i.t.) injections made into the spinal subarachnoid space inhibited bladder contractions in a dose-dependent manner. The methods for spinal and supraspinal drug administrations are described as is the estimation of the spread of drug as determined by i.c.v. and i.t. dye injections. The pharmacology of the i.c.v. and i.t. effects of opioids was determined by use of selective opioid agonists (mu-agonists: morphine, DAGO; delta-agonists: DADLE, DPDPE; kappa-agonist: U-50, 488H) and antagonists (mu-antagonist, naloxone; delta-antagonist, ICI 174,864). It was concluded that the i.c.v. and i.t. effects were mediated by mu- and delta-opioid receptors and not by kappa-receptors. A number of other agents such as pentobarbital, haloperidol, and desipramine also inhibited bladder activity following i.c.v. and i.t. administration, but their actions were insensitive to naloxone. This in vivo model was considered useful in the detection and evaluation of the central actions of substances with opioid properties.
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D000818:Animals; D002490:Central Nervous System / Q000187:drug effects*; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D008722:Methods; D009020:Morphine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*; D001743:Urinary Bladder / Q000187:drug effects*
D004745:Enkephalins; D011957:Receptors, Opioid; D009020:Morphine