Age-dependent impairment of K(ATP) channel function following brain injury.
Previous studies observed that endothelin-1 (ET-1) contributed to ATP-sensitive K+ (K(ATP)) channel impairment 1 h following fluid percussion brain injury (FPI) in the newborn pig. The present study was designed to determine the effect of FPI on K(ATP) channel activity as a function of time in newborn (1-5 days old) and juvenile (3-4 weeks old) pigs equipped with a closed cranial window. FPI of moderate severity (1.9-2.1 atm) was produced by using a pendulum to strike a piston on a saline-filled cylinder that was fluid coupled to the brain via a hollow screw inserted through the cranium. Cromakalim, a K(ATP) agonist, produced dilation that was blunted for at least 72 h post FPI, but dilator responsiveness was restored within 168 h post FPI in the newborn pig (15+/-1% and 27+/-2% vs. 5+/-1% and 11+/-1% vs. 13+/-1% and 26+/-2% for responses to 10(-8), 10(-6) M cromakalim before, and 72 and 168 h after FPI). Similar inhibited responses were observed for calcitonin gene-related peptide, 8-Bromo cGMP, and the nitric oxide (NO) releasers SNP and SNAP. In contrast, cromakalim-induced dilation was blunted for at least 4 h, but dilator responsiveness was restored within 8 h post FPI in the juvenile pig (15+/-1% and 27+/-1% vs. 9+/-1% and 15+/-2% vs. 18+/-1% and 28+/-1% for 10(-8), 10(-6) M cromakalim before, and 4 and 8 h post FPI). Similar inhibition of dilations of other agonists also occurred in the juvenile. CSF ET-1 increased to a greater level and remained elevated for a longer period of time in the newborn compared to the juvenile pig. BQ123, an ET-1 antagonist, pretreatment partially restored decremented agonist induced dilation following FPI in the newborn and juvenile pig (5+/-1% and 11+/-1% vs. 11+/-1% and 21+/-1% for responses to 10(-8), 10(-6) M cromakalim 72 h post FPI in the newborn in the absence and presence of BQ123). These data indicate that K(ATP) channel function is impaired to a greater extent and for a longer time period in the newborn versus the juvenile pig. These data also show that ET-1 contributes to such impaired vascular responsiveness to a greater extent in the newborn versus the juvenile pig. These data furthermore suggest that the newborn is more sensitive to traumatic vascular injury than the juvenile.
Armstead
W M
WM
Department of Anesthesia, University of Pennsylvania and The Children's Hospital of Philadelphia, 19104, USA. armsteawemail.med.upenn.edu.
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001160:Arterioles / Q000187:drug effects / Q000503:physiopathology; D001921:Brain / Q000254:growth & development / Q000503:physiopathology*; D001930:Brain Injuries / Q000503:physiopathology*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D019806:Cromakalim / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000134:cerebrospinal fluid; D005260:Female; D008297:Male; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010841:Pia Mater / Q000098:blood supply; D015221:Potassium Channels / Q000502:physiology*; D026423:S-Nitroso-N-Acetylpenicillamine; D013552:Swine; D014664:Vasodilation / Q000187:drug effects
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D020030:Nitric Oxide Donors; D010456:Peptides, Cyclic; D015221:Potassium Channels; C110881:S-nitro-N-acetylpenicillamine; D019806:Cromakalim; C016276:8-bromocyclic GMP; D026423:S-Nitroso-N-Acetylpenicillamine; D010396:Penicillamine; D006152:Cyclic GMP; D015740:Calcitonin Gene-Related Peptide; C072247:cyclo(Trp-Asp-Pro-Val-Leu)