title: Oxytocin in the periaqueductal gray participates in pain modulation in the rat by influencing endogenous opiate peptides.
abstract: Periaqueductal gray (PAG) plays a very important role in pain modulation through endogenous opiate peptides including leucine-enkephalin (L-Ek), methionine-enkephalin (M-Ek), β-endorphin (β-Ep) and dynorphin A(1-13) (DynA(1-13)). Our pervious study has demonstrated that intra-PAG injection of oxytocin (OXT) increases the pain threshold, and local administration of OXT receptor antagonist decreases the pain threshold, in which the antinociceptive role of OXT can be reversed by pre-PAG administration of OXT receptor antagonist. The experiment was designed to investigate the effect of OXT on endogenous opiate peptides in the rat PAG during the pain process. The results showed that (1) the concentrations of OXT, L-Ek, M-Ek and β-Ep, not DynA(1-13) in the PAG perfusion liquid were increased after the pain stimulation; (2) the concentrations of L-Ek, M-Ek and β-Ep, not DynA(1-13) in the PAG perfusion liquid were decreased by the OXT receptor antagonist; (3) the increased pain threshold induced by the OXT was attenuated by naloxone, an opiate receptor antagonist; and (4) the concentrations of L-Ek, M-Ek and β-Ep, not DynA(1-13) in the PAG perfusion liquid were increased by exogenous OXT administration. The data suggested that OXT in the PAG could influence the L-Ek, M-Ek and β-Ep rather than DynA(1-13) to participate in pain modulation, i.e. OXT in the PAG participate in pain modulation by influencing the L-Ek, M-Ek and β-Ep rather than DynA(1-13).
authors: College of Pharmacy, Xinxiang Medical University, Xixiang, Henan 453003, China.
authors: Jun
authors: J
authors: Yang
authors: Jin-Ying
authors: JY
authors: Liang
authors: Peng
authors: P
authors: Li
authors: Yan-Juan
authors: YJ
authors: Pan
authors: Pei-Yong
authors: PY
authors: Qiu
authors: Jing
authors: J
authors: Zhang
authors: Fang
authors: F
authors: Hao
authors: Da-Xin
authors: DX
authors: Wang
mesh_terms: D000818:Animals; D002404:Catheterization; D004399:Dynorphins / Q000032:analysis / Q000096:biosynthesis; D004743:Enkephalin, Leucine / Q000032:analysis / Q000096:biosynthesis; D004744:Enkephalin, Methionine / Q000032:analysis / Q000096:biosynthesis; D008845:Microinjections / Q000379:methods*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology*; D010146:Pain; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D010446:Peptide Fragments / Q000032:analysis / Q000096:biosynthesis; D010487:Periaqueductal Gray / Q000187:drug effects / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000032:analysis / Q000096:biosynthesis
chemical_list: D009292:Narcotic Antagonists; D010446:Peptide Fragments; D009270:Naloxone; D010121:Oxytocin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; C026843:dynorphin (1-13); D004399:Dynorphins