The concentration of β-endorphin-immunoreactivity (β-END-IR) and monoamine metabolites which are 3-methoxy-4-hydroxy-phenylglycol (MHPG), homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) were measured in cerebrospinal fluid (CSF) of patients with intractable pain to estimate the participation of these substances in the mechanism of intractable pain.
The amount of β-END-IR and monoamine metabolites was measured with radioimmunoas-say and HPLC (hight performance liquid chromatography), respectively.
Eight cases of intractable pain were treated with impantation of the stimulating electrode for pain relief. This treatment was performed in 2 ways, deep brain stimulation (DBS) done on 6 cases and spinal dorsal column stimualtion (DCS) on 2 cases. The concentrations of β-END-IR and monoamine metabolites were also estimated before and after the stimulation. No patient treated with DBS showed the elevation of β-END-IR or monoamine metabolites after the stimulation, except for one patient who showed significant increase of monoamine metabolites accompanying excellent pain relief by the stimulation. On the other hand, the two patients treated with DCS indicated significant elevation of β-END-IR as well as monoamine metabolites. Thus, both β-END and monoamines could play as important role DCS, and that monoamine could be involved in DBS for pain relief.