Peak B endorphin concentration in cerebrospinal fluid: reduced in chronic pain patients and increased during the placebo response.
The level of an endogenous opioid (peak B endorphin) was measured in chromatographically fractionated cerebrospinal fluid (CSF) sampled from two groups of chronic pain patients before and after intrathecal saline (placebo) injection. As assessed by a verbal rating scale, one group reported no change in their level of pain (non-responders, NR; n = 6) while the other group reported complete or greater than 50% pain relief (placebo responders, PR; n = 14). We find, as has been reported previously, that initial peak B levels were lower (by 50%) in these chronic pain patients' CSF than in CSF from pain-free (PF) normal controls (P less than 0.001, t-test). Peak B levels measured from CSF of the NR group undergoing this procedure did not change (P greater than 0.4, paired t-test). In contrast, a significant 2.3-fold increase was measured in the CSF peak B level of the PR group (P less than 0.05, paired t-test). This is the first direct evidence that a CSF opioid is correlated with placebo pain relief in chronic pain patients. Peak B is a potent analgesic substance when administered by the intracerebroventricular route in mice and its level is related to the patients' pain status in a presumably causal manner.
Lipman
J J
JJ
Department of Biochemistry, University of Tennessee Center for the Health Sciences, Memphis 38163.
Miller
B E
BE
Mays
K S
KS
Miller
M N
MN
North
W C
WC
Byrne
W L
WL
D002908:Chronic Disease; D006801:Humans; D007276:Injections, Intraventricular; D010146:Pain / Q000134:cerebrospinal fluid*; D010919:Placebos; D001615:beta-Endorphin / Q000134:cerebrospinal fluid*
D010919:Placebos; D001615:beta-Endorphin