The effect of acute kainic acid treatment on mu-opioid receptors in rat brain.
There is evidence that acute exposure to kainic acid (KA) induces the release of endogenous ligands for opioid receptors and that mu-opioid agonists intensify KA-induced neurodegeneration. The aim of the present study was to investigate any acute toxic effects of KA upon mu-opioid receptors labelled with [3H]-DAMGO. 200-250 g rats were injected intraperitoneally with either saline or 16 mg/kg KA and brains were removed after 4 h. Membrane homogenates were prepared from the cerebellum, cortex, hippocampus, medulla and pons, midbrain and hypothalamus and striatum and in separate studies, from whole brain. In addition, frozen coronal sections were processed for comparative quantitative autoradiography. KA produced a two-fold increase in receptor affinity for [3H]-DAMGO in all regions and significant increases in receptor number in cortex, medulla and pons and striatum. Quantitative autoradiography showed similar significantly increased mu-labelling of structures comprising these gross anatomical regions. The findings demonstrate region specific changes in rat brain mu-opioid receptors after acute KA treatment which may be functionally related to the convulsant effects of this excitotoxin.
Ridd
M J
MJ
Pharmacology Research Group, School of Biological Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, UK.
Fosbraey
P
P
Kitchen
I
I
D000818:Animals; D001921:Brain / Q000187:drug effects*; D007608:Kainic Acid / Q000633:toxicity*; D016014:Linear Models; D008297:Male; D009410:Nerve Degeneration; D009498:Neurotoxins / Q000633:toxicity*; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000819:agonists*
D009498:Neurotoxins; D017450:Receptors, Opioid, mu; D007608:Kainic Acid