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Non-NMDA receptor antagonist-induced drinking in rat
1Departments of Psychology and Pharmacology, and The Cardiovascular Center, 11 Seashore Hall E, University of Iowa, Iowa City, IA 52242-1407, USA.
Brain Research
|October 31, 1998
Summary
Non-NMDA receptor antagonists, DNQX and CNQX, trigger drinking in rats. This effect suggests non-NMDA receptors may inhibit thirst pathways, requiring NMDA receptor function.
Area of Science:
- Neuroscience
- Physiology
- Neuropharmacology
Background:
- Glutamate plays a role in regulating body fluid balance.
- Understanding the central control of thirst is crucial for fluid homeostasis.
Purpose of the Study:
- To investigate the role of non-N-methyl-D-aspartate (NMDA) receptors in the central control of drinking behavior.
- To determine the involvement of NMDA and other receptor systems in mediating the dipsogenic effects of non-NMDA receptor antagonists.
Main Methods:
- Intracerebroventricular (i.c.v.) injections of non-NMDA receptor antagonists (DNQX, CNQX) in rats.
- Administration of non-NMDA receptor agonist (AMPA) and NMDA receptor antagonist (MK-801) for antagonism studies.
- Testing the effects of angiotensin type 1 (AT1) and acetylcholine muscarinic receptor antagonists (losartan, atropine).
Main Results:
- i.c.v. DNQX and CNQX induced significant water intake in rats.
- The dipsogenic effect of DNQX was blocked by AMPA, indicating non-NMDA receptor involvement.
- NMDA receptor antagonist MK-801 blocked DNQX-induced drinking, while AT1 and muscarinic antagonists had no effect.
Conclusions:
- Non-NMDA receptors may exert tonic inhibitory control over brain circuits regulating thirst.
- Functional NMDA receptors appear necessary for non-NMDA receptor antagonists to elicit drinking behavior.
- These findings elucidate novel mechanisms in the central regulation of fluid intake and thirst.