Effects of [N- (L- (1-carboxy-2-phenyl) ethyl]-L-phenylalanyl-beta-alanine (SCH32615) , a neutral endopeptidase (enkephalinase) inhibitor, on levels of enkephalin, encrypted enkephalins and substance P in cerebrospinal fluid and plasma of primates
Yaksh, T.L.; Sabbe, M.B.; Lucas, D.; Mjanger, E.; Chipkin, R.E.
Journal of Pharmacology and Experimental Therapeutics 256(3): 1033-1041
1991
ISSN/ISBN: 0022-3565 PMID: 1706428 Document Number: 367736
In halothane-anesthetized and -ventilated cynomologus macaque monkeys, the effects of administering vehicle (n = 3) or the neutral endopeptidase inhibitor N-[L-(1-carboxy-2-phenyl)ethyl]-L-phenylalanyl-beta-alanine (16 mg/kg, n = 5; or 100 mg/kg, n = 3, intravenously) was examined. Cisternal CSF aliquots were examined by radioimmunoassay: 1) for Met enkephalin; 2) after trypsin and carboxypeptidase B treatment for encrypted enkephalin (X-ENK); 3) for substance P; and 4) for unmetabolized drug. Similar measures were carried out in femoral artery and femoral venous plasma, except that substance P was not assayed. In CSF, prior to drug, low, but measurable levels of enkephalin (61 pg/ml), X-ENK (285 pg/ml) and substance P (16 pg/ml) were observed. Vehicle-injected animals showed no change from baseline levels over a 4-hr sampling period in either plasma or CSF levels. In contrast, following 16 mg/kg, in CSF, there was a significant 9-fold increase in MET and 11-fold increase in X-ENK at 30 min. CSF-substance P levels rose also by a factor of 2, with the peak effect observed at 60 min. All levels displayed a significant reduction by 4 hr. There was no statistical difference between the maximum effects observed with either the 16- or 100-mg/kg dose. Plasma peptide levels of enkephalin and X-ENK were not altered by drug. CSF displayed significant drug levels by 30 min, which were between 0.1 and 1% of levels observed concurrently in plasma.