title: Postnatal development of opioid regulation of micturition in the kitten.
abstract: Endogenous opioids tonically regulate micturition in adult mammals. The present study sought to determine if opioids regulate micturition in neonatal kittens. Naloxone (up to 2 mg/kg given i.p. or i.v. to unanesthetized/ketamine-anesthetized or chloralose-anesthetized kittens, respectively), an opioid receptor antagonist, produced no effects in unanesthetized, ketamine-anesthetized, or chloralose-anesthetized kittens that had been prepared for bladder pressure recording, until 3 weeks of age. This indicates that endogenous opioids are not tonically regulating micturition in neonatal kittens. From 3 weeks up to at least 6 weeks of age, naloxone (100 micrograms/kg i.p. or i.v.) weakly facilitated bladder activity by transiently increasing the amplitude and/or duration of bladder contractions, but no effects on frequency of contractions was recorded. Morphine (up to 2 mg/kg given i.p. or i.v. to unanesthetized/ketamine-anesthetized or chloralose-anesthetized kittens, respectively), an opioid agonist, did not inhibit bladder contractions in unanesthetized or ketamine-anesthetized neonatal kittens, but it did inhibit (at a threshold dose of 100 micrograms/kg) and completely abolished (at a dose of 300 micrograms/kg) bladder activity in chloralose-anesthetized kittens in a dose-dependent, naloxone-reversible manner. Surprisingly, following morphine administration to unanesthetized or ketamine-anesthetized neonatal kittens, naloxone now produced an adult-like enhancement of bladder activity. These latter results indicate that opioid receptors, whose inhibitory effects are anesthetic-dependent, are present along the micturition reflex pathway in neonates. Immunohistochemical studies of the sacral spinal cord revealed that opioid peptides are distributed similarly in neonatal and adult cats.
authors.affiliation: Lilly Research Laboratories, Division of CNS Research, Indianapolis, IN 46285.
authors.forename: K B
authors.initials: KB
authors.lastname: Thor
authors.forename: D P
authors.initials: DP
authors.lastname: Blais
authors.forename: M
authors.initials: M
authors.lastname: Kawatani
authors.forename: S
authors.initials: S
authors.lastname: Erdman
authors.forename: W C
authors.initials: WC
authors.lastname: de Groat
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D002415:Cats; D004723:Endorphins / Q000502:physiology*; D004743:Enkephalin, Leucine / Q000494:pharmacology; D005726:Ganglia, Parasympathetic / Q000254:growth & development; D007150:Immunohistochemistry; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D012018:Reflex / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development; D013194:Staining and Labeling; D001743:Urinary Bladder / Q000254:growth & development / Q000294:innervation; D014554:Urination / Q000502:physiology*
chemical_list: D004723:Endorphins; D009270:Naloxone; D004743:Enkephalin, Leucine; D009020:Morphine