Repeated cocaine administration increases nitric oxide efflux in the rat dorsal striatum.
BACKGROUND
Repeated injections of cocaine alter extracellular nitric oxide (NO) efflux via interactions between dopamine and glutamate receptor-coupled signaling cascades.


OBJECTIVE
Putative cellular mechanisms underlying changes in NO efflux following repeated cocaine administration were investigated.


METHODS
Real-time detection of NO efflux using a NO biosensor was mainly performed in the rat dorsal striatum in vivo.


RESULTS
Repeated exposure to cocaine (20 mg/kg), once a day for seven consecutive days, increased NO levels. Repeated injections of cocaine also increased the phosphorylation of neuronal nitric oxide synthase (nNOS), and inhibition of nNOS decreased the repeated cocaine-evoked increases in NO levels. Inhibition of protein kinase A, but not protein phosphatases, synergistically increased NO levels elevated by repeated cocaine injections. Blockade of dopamine D1 (D1) receptors or stimulation of dopamine D2 (D2) receptors decreased the repeated cocaine-evoked increases in NO levels. Similarly, blockade of N-methyl-D: -aspartate (NMDA) receptors and group I metabotropic glutamate receptors (mGluRs) or stimulation of group III mGluRs also decreased the repeated cocaine-evoked increases in NO levels.


CONCLUSIONS
Stimulation of D1 receptors or group I mGluRs following repeated cocaine administration upregulates NO efflux via an NMDA receptor-evoked Ca2+ influx, while stimulation of D2 receptors or group III mGluRs downregulates NO efflux. Dephosphorylation of phosphorylated nNOS by protein phosphatases is necessary for upregulating NO efflux in the dorsal striatum after repeated cocaine administration.
Lee
Dong Kun
DK
Department of Biological Sciences, Pusan National University, 30 Jangjeon-dong, Kumjeong-gu, Pusan, 609-735, South Korea.
Koh
Wei Choon Alvin
WC
Shim
Yoon-Bo
YB
Shim
Insop
I
Choe
Eun Sang
ES
D000818:Animals; D001479:Basal Ganglia / Q000187:drug effects* / Q000378:metabolism; D015374:Biosensing Techniques; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D003042:Cocaine / Q000008:administration & dosage*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007263:Infusions, Parenteral; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
D000697:Central Nervous System Stimulants; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D003042:Cocaine