THE EFFECT OF ACUTE KAINIC ACID TREATMENT ON DOPAMINE D-2 RECEPTORS IN RAT-BRAIN

Acute exposure to kainic acid (KA) induces neurochemical changes in do paminergic systems in the brain and the aim of the present study was t o investigate the acute toxicity of KA upon dopamine D-2 receptors. Ad ult rats were injected intraperitoneally with either saline or 16 mg/k g KA. Brains were removed after 4 h. Membrane homogenates were prepare d from seven brain regions and in addition, frozen coronal sections we re sectioned for comparative quantitative autoradiographic analysis. D opamine D-2 receptors were characterised by saturation studies using [ I-125]iodosulpiride, [H-3]raclopride and [H-3]spiperone. KA produced a 2-fold decrease in receptor affinity for [I-125]iodosulpiride and a 2 -fold increase in receptor density in all regions studied except stria tum. Quantitative autoradiography with [I-125]iodosulpiride showed sim ilar increases in D-2 labelling following KA except in caudate putamen , nucleus accumbens and olfactory tubercle. In contrast, there was no change in [H-3]spiperone binding in whole brain minus striatum nor in striatum alone after KA treatment. KA produced a significant increase in B-max for [H-3]raclopride in whole brain minus striatum and in stri atum alone with minimal changes in affinity. These findings demonstrat e acute changes in rat brain dopamine D-2 receptors labelled with [I-1 25]iodosulpiride and [H-3]raclopride but not [H-3]spiperone after ECA treatment predominantly in extra striatal regions. (C) 1998 Elsevier S cience Ireland Ltd. All rights reserved.