Dizocilpine inhibits amphetamine-induced formation of nitric oxide and amphetamine-induced release of amino acids and acetylcholine in the rat brain

Influence of a Nitric Oxide Synthase Inhibitor on the Anxiolytic, Stimulating, and Analgesic Effects of Long-Term Perinatal Caffeine Exposure in Rats

We studied the effect of inducible NO synthase (iNOS) inhibitor aminoguanidine on the behavioral effects of chronic perinatal caffeine exposure. Administration of caffeine in the prenatal and early postnatal periods led to the development of anxiolytic, stimulating, and analgesic effects. Administration of aminoguanidine attenuated the anxiolytic and stimulating effects and potentiated the analgesic effect of perinatal administration of caffeine. Chronic perinatal administration of caffeine leads to significant changes in the level of anxiety, motor activity, and pain sensitivity, and inhibition of iNOS has a pronounced multidirectional effect on these effects.

Role of nitric oxide in psychostimulant-induced neurotoxicity

In recent decades, consumption of psychostimulants has been significantly increased all over the world, while exact mechanisms of neurochemical effects of psychomotor stimulants remained unclear. It is assumed that the neuronal messenger nitric oxide (NO) may be involved in mechanisms of neurotoxicity evoked by psychomotor stimulants. However, possible participation of NO in various pathological states is supported mainly by indirect evidence because of its short half-life in tissues. Aim of this review is to describe the involvement of NO and the contribution of lipid peroxidation (LPO) and acetylcholine (ACH) release in neurotoxic effects of psychostimulant drugs. NO was directly determined in brain structures by electron paramagnetic resonance (EPR). Both NO generation and LPO products as well as release of ACH were increased in brain structures following four injections of amphetamine (AMPH). Pretreatment of rats with the non-selective inhibitor of NO-synthase (NOS) N-nitro-L-arginine or the neuronal NOS inhibitor 7-nitroindazole significantly reduced increase of NO generation as well as the rise of ACH release induced by AMPH. Both NOS inhibitors injected prior to AMPH had no effect on enhanced levels of LPO products. Administration of the noncompetitive NMDA receptor antagonist dizocilpine abolished increase of both NO content and concentration of LPO products induced by of the psychostimulant drug. Dizocilpine also eliminated the influence of AMPH on the ACH release. Moreover, the neurochemical and neurotoxic effects of the psychostimulant drug sydnocarb were compared with those of AMPH. Single injection of AMPH showed a more pronounced increase in NO and TBARS levels than after an equimolar concentration of sydnocarb. The findings demonstrate the crucial role of NO in the development of neurotoxicity elicited by psychostimulants and underline the key role of NOS in AMPH-induced neurotoxicity.

Clinical physiology and mechanism of dizocilpine (MK-801): electron transfer, radicals, redox metabolites and bioactivity

Dizocilpine (MK-801), an extensively investigated drug possessing secondary amine and benzenoid functions, displays a wide array of biological properties, including anticonvulsant and anesthetic. There is scant discussion of biomechanism. A relevant, important finding is formation of oxidative metabolites in the hydroxylamine and phenolic categories. Analogy to cocaine metabolites suggests participation of redox entities, such as, hydroxylamine, nitroxide and nitrosonium, which can lead to electron transfer and radical formation. There is also similarity to metabolism by 3,3′-iminodipropionitrile and phencyclidine. Alternatively, the phenolic metabolites are well-known precursors of ET quinones. The review documents various physiological effects, mainly involving the central nervous system. Also of interest are the pro- and anti-oxidant properties. Considerable attention has been paid to MK-801 as an antagonist of the N-methyl-D-aspartate receptor in the glutamate category. This aspect is often associated with effects on the central nervous system. The review also provides recent literature dealing with MK-801/NMDA receptor in various areas of bioactivity. Studies were made of MK-801 involvement in working memory processing. Deficits in behavior were noted after administration of the drug. Treatment of mice with dizocilpine induced learning impairment. The influence of MK-801 on fear has been investigated. The substance is known to exert an analgesic effect in pain control. A number of reports deal with anesthetic properties.

cGMP: a second messenger for acetylcholine in the brain?

Already 30 years ago, it became apparent that there exists a relationship between acetylcholine and cGMP in the brain. Acetylcholine plays a role in a great number of processes in the brain, however, the role of cGMP in these processes is not known. A review of the data shows that, although the connection between NO-mediated cGMP synthesis and acetylcholine is firmly established, the complexities of the heterosynaptic pathways and the oligosynaptic structures involved preclude a clear definition of the role of cGMP in the functioning of acetylcholine presently.

Comparative Effects of NO-Synthase Inhibitor and NMDA Antagonist on Generation of Nitric Oxide and Release of Amino Acids and Acetylcholine in the Rat Brain Elicited by Amphetamine Neurotoxicity

The aim of this study was to clarify the role of nitric oxide (NO) and lipid peroxidation (LPO) processes as well as the contribution of various neurotransmitters in pathophysiological mechanisms of neurotoxicity induced by amphetamine (AMPH). NO level was determined directly in brain tissues using electron paramagnetic resonance spectroscopy technique. The content of the products of lipid peroxidation (LPO) was measured spectrophotometrically as thiobarbituric acid reactive species (TBARS). The output of neurotransmitter amino acids (glutamate, aspartate, and GABA) and acetylcholine (ACH) was monitored in nucleus accumbens (NAc) by push-pull technique with HPLC detection. Repeated, systemic application of AMPH elevated striatal and cortical NO generation and LPO production. Moreover, administration of AMPH led to a marked and long-lasting increase of ACH release. Surprisingly, while glutamate output was not affected, aspartate release was enhanced 30 to 50 min after each AMPH injection. The release rate of GABA was also elevated. The selective NO-synthase inhibitor 7-nitroindazole (7-NI) was highly effective in abating the rise in the neurotransmitter release induced by the AMPH. The NOS inhibitor also abolished the increase of NO generation produced by AMPH, but did not influence the intensity of LPO elicited by the AMPH administration. Pretreatment with the noncompetitive NMDA receptor antagonist dizocilpine (MK-801) completely prevented increase of NO generation and TBARS formation induced by multiple doses of AMPH. Dizocilpine also abolished the effect of the psychostimulant drug on the release of neurotransmitters ACH, glutamate, aspartate, and GABA in the NAc. Our findings suggest a key role of NO in AMPH-induced transmitter release, but not in the formation of LPO products. It appears that AMPH enhances release of ACH and neurotransmitter amino acids through increased NO synthesis and induces neurotoxicity via NO and also by NO-independent LPO.