2--hydroxy-5-9-dimethyl-2-allyl-6-7-benzomorphan and 2-amino-7-phosphonoheptanoic-acid

Behavioral effects of PCP-type noncompetitive antagonists of N-methyl-D-aspartate (NMDA) receptors overlap with those of a host of other centrally acting compounds. In the present experiment, locomotor activity and performance on an inverted screen test in untrained mice were used to differentiate PCP-type non-competitive NMDA antagonists from other drug classes. These uncompetitive NMDA antagonists [PCP, dizocilpine, (-)-MK-801, TCP, (+)-SKF 10,047, dextrorphan, ketamine] produced dose-related increases in locomotor activity and the percentage of mice falling off an inverted, elevated wire mesh screen. Both effects demonstrated stereoselectivity, occurred at comparable dose levels, and were within the range of doses producing other biological effects (e.g., anticonvulsant). The potencies of these drugs for producing behavioral effects were positively correlated with affinities for PCP ([3H]MK-801) but not sigma([3H]SKF 10,047) receptors. Although muscarinic antagonists (benactyzine, atropine) produced effects in the same direction, locomotor stimulation was small and occurred at lower doses than those inducing screen failures. Competitive NMDA antagonists (LY 274614, LY 233536, CPP, NPC 12626), sigma receptor ligands (DTG, dextromethorphan), postsynaptic dopamine agonists (quinpirole, SKF 38393) and antagonists (haloperidol, SCH 39166), and some depressant compounds (morphine, diazepam) increased failures on the screen test but decreased locomotor activity. Ligands of the polyamine regulatory site of the NMDA receptor (ifenprodil, SL 82.0715-10) and the AMPA receptor antagonist NBQX decreased locomotor activity without increasing screen failures. An antagonist of the strychnine-insensitive glycine receptor (7-chlorokynurenic acid) did not affect performance on either test. Psychomotor stimulants (cocaine and methamphetamine) stimulated locomotor activity without affecting screen performance. The only false positives occurred with barbiturates (pentobarbital, phenobarbital). Nonetheless, the present procedure demonstrates excellent sensitivity and power for rapid discrimination of uncompetitive NMDA antagonists.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Anticonvulsants; Behavior, Animal; Binding, Competitive; Central Nervous System Depressants; Dose-Response Relationship, Drug; Male; Mice; Motor Activity; Phenazocine; Receptors, N-Methyl-D-Aspartate; Receptors, Phencyclidine

In the present study the effect of L-glutamic acid (L-Glu), N-methyl-D-aspartic acid (NMDA), kainic acid (KA) and quisqualic acid (QUIS) on the release of endogenous dopamine (DA) from slices of the rat caudate-putamen was investigated. DA was measured by high-performance liquid chromatography coupled to an electrochemical detector. L-Glu, NMDA, KA and QUIS, in the absence of Mg++, produced a dose-related, Ca++-dependent increase in DA release. The order of agonist efficacy was L-Glu greater than NMDA greater than KA = QUIS. D-2-amino-7-phosphonoheptanoic acid (0.5 mM), but not L-2-amino-7-phosphonoheptanoic acid, antagonized the action of L-Glu and NMDA, but did not modify the effect of KA or QUIS. Tetrodotoxin (0.1 microM) partially inhibited the stimulatory effect of KA and QUIS, but not that of L-Glu or NMDA. Mg++ (1.2 mM) abolished the excitatory effect of NMDA, significantly reduced the action of L-Glu, but did not influence the action of KA or QUIS. The inhibitory action of Mg++ on the L-Glu-induced DA release was reversed when L-Glu was coupled to high concentrations of K+. N-allylnormetazocine (SKF-10,047), a benzmorphan agent, produced a stereospecific inhibition of L-Glu-induced DA release. This inhibition was also produced by 1-[1-(2-thienyl)cyclohexyl]piperidine, a phencyclidine receptor ligand, but not by 1,3-di-O-tolylguanidine, a sigma receptor-selective ligand. The results of this study show that L-Glu increases DA release predominantly by activation of the NMDA receptor located presynaptically on dopaminergic afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Aspartic Acid; Caudate Nucleus; Dopamine; Dose-Response Relationship, Drug; Glutamates; Glutamic Acid; In Vitro Techniques; Magnesium; Male; N-Methylaspartate; Oxadiazoles; Phenazocine; Potassium; Putamen; Quisqualic Acid; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter