Measurement of enkephalin peptides in canine brain regions, teeth, and cerebrospinal fluid with high-performance liquid chromatography and mass spectrometry.

Endogenous enkephalin pentapeptides are measured with unambiguous molecular specificity in canine and human tissue and fluid extracts. Both field desorption and fast atom bombardment mass spectrometry have been used to produce a protonated molecular ion of the peptide high-performance liquid chromatography fraction. The protonated molecular ion is subjected to collision-activated dissociation processes and a linked-field scan (B/E) selects a unique amino acid sequence-determining ion for monitoring and measurement. Stable isotope-incorporated peptide internal standards are used for quantification. Endogenous enkephalins are measured in hypothalamus, cerebrospinal fluid, pituitary, caudate nucleus, and tooth pulp extracts. Part-per-billion levels of endogenous peptide are measured.