Increase in the Extracellular Histamine Concentration in the Rat Striatum by μ-Opioid Receptor Activation
Article first published online: 23 NOV 2002
Journal of Neurochemistry
Volume 62, Issue 2, pages 724–729, February 1994
How to Cite
Chikai, T., Oishi, R. and Saeki, K. (1994), Increase in the Extracellular Histamine Concentration in the Rat Striatum by μ-Opioid Receptor Activation. Journal of Neurochemistry, 62: 724–729. doi: 10.1046/j.1471-4159.1994.62020724.x
- Issue published online: 23 NOV 2002
- Article first published online: 23 NOV 2002
- Received May 5, 1993; revised manuscript received July 8, 1993; accepted July 12, 1993.
- Freely moving rat;
Abstract: 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-Ala2,MePhe4,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-Pen2,d-Pen5]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.