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Crucial role of kainate receptors in mediating striatal kainate injection-induced decrease in acetylcholine M(1)
1Department of Pharmacology, Faculty of Medicine, The National University of Singapore, MD2, 18 Medical Drive, 117597, Singapore, Singapore. phcjinsy@nus.edu.sg
Brain Research
|November 1, 2000
Summary
Striatal kainate injections decrease acetylcholine M(1) receptor binding in rats, involving kainate and N-methyl-D-aspartate (NMDA) receptors. This highlights kainate receptors' role in regulating excitatory amino acid-modulated cholinergic neurotransmission in the CNS.
Area of Science:
- Neuroscience
- Neuropharmacology
- Receptor Binding Studies
Background:
- Cholinergic neurotransmission is modulated by excitatory amino acids (EAAs) in the central nervous system (CNS).
- The roles of specific glutamate receptor subtypes, including kainate, AMPA, and NMDA receptors, in this modulation are not fully elucidated.
Purpose of the Study:
- To investigate the involvement of kainate, AMPA, and NMDA receptors in the decrease of acetylcholine M(1) receptor binding induced by striatal kainate injection in rats.
- To elucidate the mechanisms underlying EAA-modulated cholinergic neurotransmission.
Main Methods:
- Unilateral intrastriatal kainate injections in rats.
- Measurement of [3H]kainate, [3H]MK-801, and [3H]pirenzepine binding to rat forebrain membranes over time.
- Saturation binding studies to determine receptor density (Bmax) and affinity (Kd).
- Administration of selective NMDA receptor antagonist (MK-801), non-NMDA receptor antagonist (CNQX), and AMPA receptor potentiator (Cyclothiazide) to assess their effects on kainate-induced binding changes.
Main Results:
- Striatal kainate injection significantly decreased the binding of [3H]kainate, [3H]MK-801, and [3H]pirenzepine, with maximal effects observed 2-4 days post-injection.
- Kainate dose-dependently reduced Bmax and Kd values for all three ligands.
- NMDA receptor antagonist MK-801 partially antagonized kainate-induced binding decreases, while non-NMDA receptor antagonist CNQX almost completely abolished them.
- AMPA receptor potentiator Cyclothiazide enhanced the decrease in [3H]kainate binding but not other ligands.
Conclusions:
- The decrease in acetylcholine M(1) receptor binding following striatal kainate injection is primarily dependent on kainate receptor activation, with a secondary involvement of NMDA receptors.
- These findings suggest that kainate receptors play a critical role in regulating EAA-mediated cholinergic neurotransmission within the CNS.