Microinjection of NMDA Receptor Agents into the Central Nucleus of the Amygdale Alters Water Intake in Rats

Document Type : Original Article


1 Department of Biology, Faculty of Science, Karaj Islamic Azad University, Karaj, Iran

2 Department of Veterinary Medicine, Karaj Islamic Azad University, Karaj, Iran


The central nucleus of the amygdala (CeA) is a forebrain structure which is important in regulation of ingestive behavior and there is direct and circumstantial evidence to indicate that some circuits involved with feeding behavior include glutamatergic elements. The present study examined whether administration of NMA (N-Methyl-DL-aspartic acid) or MK801 into the CeA altered water intake under deprivation.
Materials and Methods
Animals were deprived for 24 hr before tested for water intake. NMDA (N-methyl-D-aspartate) glutamatergic receptor agonist, NMA and its antagonist, MK801 were infused bilaterally, and water intake measured for 1 hr thereafter.
The intra-CeA injection of NMDA glutamatergic agonist, NMA (0.25, 0.5 and 0.75 pg/rat) increased water intake (P<0.05). However, administration of NMDA glutamatergic antagonist, MK801 (0.25, 0.5 and 1 pg/rat) decreased water intake significantly (P<0.05).
These data suggest that NMDA receptors in the CeA are responsible for the glutamatergic modulation of water intake in this nucleus.


1.Thongkhao-on K, Wirtshafter D, Shippy S. Feeding specific glutamate surge in the rat lateral hypothalamus revealed by low-flow push-pull perfusion. Pharmacol Biochem Behav 2008; 89:591-597.
2.DiPatrizio N, Simansky K. Activating parabrachial cannabinoid cb1 receptors selectively stimulates feeding of palatable foods in rats. J Neurosci 2008; 28:9702.
3.Cotman C, Monaghan D. Excitatory amino acid neurotransmission. Nmda receptors and hebb-type synaptic plasticity. Annu Rev Neurosci 1988;11:61-80.
4.Bergink V,van Megen H, Westenberg H.Glutamate and anxiety.Eur Neuropsychopharmacol 2004; 14:175-183.
5.Hollmann M, Heinemann S. Cloned glutamate receptors. Ann Rev Neurosci 1994; 17:31-108.
6.Zeni L, Seidler H, De Carvalho N, Freitas C, Marino-Neto J, Paschoalini M. Glutamatergic control offood intake in pigeons: Effects of central injections of glutamate, NMDA, and AMPA receptor agonists and antagonists. Pharmacol Biochem Behav 2000; 65:67.
7.Paxinos G. The rat brain in stereotaxic coordinates, 6th ed. San Diego: Elsevier Academic Press; 2007.
8.Zarrindast M, Solati J, Oryan S, Parivar K. Effect of intra-amygdala injection of nicotine and gaba receptor agents on anxiety-like behaviour in rats. Pharmacology 2008; 82:276-284.
9.Zorrilla E, Inoue K, Fekete E, Tabarin A, Valdez G, Koob G. Measuring meals: structure of prandial food and water intake of rats. Am J Physiol Regul Integr Comp Physiol 2005; 288:1450-1467.
10.Burns G, Ritter R. The non-competitive NMDA antagonist MK-801 increases food intake in rats. Pharmacol Biochem Behav 1997; 56:145-149.
11.Bednar I, Qian M, Qureshi G, Kallstrom L, Johnson A, Carrer H, Sodersten P. Glutamate inhibits ingestive behaviour. J Neuroendocrinol 1994; 6:403-408.
12.Wirtshafter D, Trifunovic R. Stimulation of ingestive behaviors following injections of excitatory amino acid antagonists into the median raphe nucleus. Pharmacol Biochem Behav 1988; 30:529-533.
13.Wirtshafter D, Krebs J. Control of food intake by kainate/quisqualate receptors in the median raphe nucleus. Psychopharmacology 1990; 101:137-141.
14.Treece R, Burns G. Lesions of the dorsal vagal complex abolish increases in meal size induced by NMDA receptor blockade. Brain Res 2000; 872:37-43.
15.Van Den Pol A, Hermans-Borgmeyer I, Hofer M, Ghosh P, Heinemann S. Ionotropic glutamate-receptor gene expression in hypothalamus: Localization of AMPA, kainate, and NMDA receptor RNA with in situ hybridization. J Comp Neurol 1994; 343: 428-44.