Simultaneous analysis of D- and L-serine in cerebrospinal fluid by use of HPLC.

BACKGROUND: D-Serine is a coagonist for the glycine-binding site of the N-methyl-D-aspartate receptors and has been implicated in various neuropsychiatric functions such as learning, memory, and nociception, as well as schizophrenia and Alzheimer disease. We developed an HPLC method for D- and L-serine in cerebrospinal fluid (CSF). METHODS: The dabsylated racemic serine peak, automatically collected using a previously reported HPLC separation process for CSF amino acids, was desalted and subjected to a chiral resolution HPLC step with a Sumichiral column using an ultraviolet-visible detector. RESULTS: The limits of quantification (signal-to-noise ratio = 10) for D- and L-serine were 0.8 and 1.3 micromol/L, respectively. The mean imprecision values (CVs) for within-day measurements of D- and L-serine were 2.1% and 1.8%, respectively, and for between-day were 6.2% and 6.6%. Mean recovery of CSF serine (sum of D-serine + L-serine) applied to the Sumichiral column was 87%. The mean (SD) d-serine concentrations in 45 CSF samples obtained from 16 patients with chronic pain due to degenerative osteoarthritis of the knees, 16 with postherpetic neuralgia, and 13 with no pain were, respectively, 3.97 (0.44), 1.85 (0.21), and 2.72 (0.32) micromol/L. CONCLUSION: D- and L-serine can be quantified with ultraviolet-visible detection of dabsyl derivatives. The dabsyl derivatives are stable and allow duplicate analysis of CSF samples in multisample runs.

Nocistatin and its derivatives antagonize the impairment of short-term acquisition induced by nociceptin.

We studied the effects of human nocistatin, a mature form of human nocistatin of 17 amino acid length (nocistatin 17), and the amide derivative of nocistain 17 (nocistatin amide), and nociceptin/orphanin FQ on short-term acquisition in mice using a multi trial passive avoidance protocol. Nociceptin 1 nmol administered by i.c.v. injection 15 min beforehand increased the number of trials required to achieve the learning objective and decreased the step through latency times in the first, second and third test trials. Nocistatin and nocistatin 17 on their own did not affect acquisition, but were able at doses of 4 nmol to antagonize the impairment caused by nociceptin 1 nmol. Nocistatin amide on its own also did not impair acquisition and at a lower dose of 1 nmol was able to completely antagonize nociceptin. [N-Phe(1)]-nociceptin (1-13) amide, a selective opioid receptor-like 1 (ORL1) receptor antagonist, could also antagonize the effect of nociceptin, confirming that nociceptin's effect is induced via the ORL1 receptor. The results support suggestions that both nocistatin and nociceptin have roles in learning and memory, with nocistatin working as a functional antagonist of nociceptin. The shorter mature human nocistatin peptide had similar activity to the larger peptide, and its amide derivative may be more potent.

Supraspinal nocistatin and its amide derivative antagonize the hyperalgesic effects of nociceptin in mice.

Nocistatin (NST) and nociceptin (NCP)/orphanin FQ are new neuropeptides derived from the same precursor molecule, and which are involved in pain transmission. Nocistatin has been shown to antagonize several effects of nociceptin by acting on a different receptor. We examined the effects of supraspinal nocistatin and nocistatin amide, and their interaction with nociceptin on nociceptive behavior in mice, using hotplate response times. We found that both nocistatin and nocistatin amide did not change the response time compared to control mice, whereas increasing doses of nociceptin caused progressive shortening of response times. Nocistatin and nocistatin amide were both able to antagonize the hyperalgesic effect of nociceptin. The effect of nocistatin amide was longer lasting and more potent, suggesting that the C-terminal free carboxyl group of nocistatin is not necessary for its biological activity, and that the amide derivative may be more biologically stable.