Substance P and [leucine]enkephalin release in guinea pig ileum during naloxone-precipitated morphine withdrawal.
This study describes the first direct demonstration that naloxone evokes the release of both substance P-like immunoreactivity (SPLI) and [Leu]enkephalin-like immunoreactivity (LELI) form opiate tolerant/dependent guinea pig ileum longitudinal muscle myenteric plexus (LMMP). The basal release of SPLI was 0.5 pg/mg of tissue per 2 min and LELI was 60 fg/mg of tissue per 2 min. Naloxone at 1 microM concentration evoked both SPLI and LELI release from in vitro as well as rapid in vivo opiate tolerant/dependent LMMP. The magnitudes were nearly double the basal release. In opiate-naive LMMP, naloxone also evoked a significant LELI release suggesting that the enkephalinergic neurons in the LMMP are under a tonic endogenous opioid inhibitory control.
Wang
F S
FS
Shanghai Institute of Materia Medica, Chinese Academy of Sciences.
Tsou
K
K
D000818:Animals; D004743:Enkephalin, Leucine / Q000378:metabolism*; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D066298:In Vitro Techniques; D009021:Morphine Dependence / Q000378:metabolism*; D009197:Myenteric Plexus / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology*; D013373:Substance P / Q000378:metabolism*; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*
D013373:Substance P; D009270:Naloxone; D004743:Enkephalin, Leucine