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Increase in the Extracellular Histamine Concentration in the Rat Striatum by μ‐Opioid Receptor Activation
Author(s) -
Chikai Takashi,
Oishi Ryozo,
Saeki Kiyomi
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.62020724.x
Subject(s) - striatum , histamine , extracellular , opioid , chemistry , receptor , medicine , neuroscience , endocrinology , pharmacology , biology , biochemistry , dopamine
The effects of morphine and selective ligands for μ‐, κ‐, and δ‐opioid receptors on the extracellular histamine (HA) concentration in the striatum of freely moving rats were examined by in vivo microdialysis. On the day after implantation of the dialysis probe, the HA output per 30‐min period was measured using HPLC‐fluorometry. Morphine (3.8 mg/kg, s.c.) significantly increased the HA output by ∼200% 1–3 h after treatment. This effect was completely antagonized by naltrexone (1.6 mg/kg, s.c.). The HA output decreased to a level below 10% of the basal value by 4 h after treatment with ( S )‐α‐fluoromethylhistidine (77 mg/kg, s.c.). In such animals, morphine (3.8 mg/kg, s.c.) had no influence on the HA output. [ d ‐Ala 2 ,MePhe 4 ,Gly(ol) 5 ]Enkephalin (DAGO; 0.2 µg, i.c.v.), a selective μ‐agonist, significantly increased the HA output by ∼150% 0.5–1.5 h after treatment, and this effect was also completely blocked by naltrexone. A selective κ‐agonist, U‐50,488 (3.8 and 7.6 mg/kg, s.c.), and a selective δ‐agonist, [ d ‐Pen 2 , d ‐Pen 5 ]enkephalin (0.5 and 2 µg, i.c.v.), had no effect on the HA output. These findings suggest that the stimulation of μ‐opioid receptors by morphine and DAGO increases the extracellular HA concentration by accelerating HA release from nerve endings.