Nanoscale electrochemical kinetics & dynamics: the challenges and opportunities of single-entity measurements.

The development of nanoscale electrochemistry since the mid-1980s has been predominately coupled with steady-state voltammetric (i-E) methods. This research has been driven by the desire to understand the mechanisms of very fast electrochemical reactions, by electroanalytical measurements in small volumes and unusual media, including in vivo measurements, and by research on correlating electrocatalytic activity, e.g., O2 reduction reaction, with nanoparticle size and structure. Exploration of the behavior of nanoelectrochemical structures (nanoelectrodes, nanoparticles, nanogap cells, etc.) of a characteristic dimension λ using steady-state i-E methods generally relies on the well-known relationship, λ2 ∼ Dt, which relates diffusional lengths to time, t, through the coefficient, D. Decreasing λ, by performing measurements at a nanometric length scales, results in a decrease in the effective timescale of the measurement, and provides a direct means to probe the kinetics of steps associated with very rapid electrochemical reactions. For instance, steady-state voltammetry using a nanogap twin-electrode cell of characteristic width, λ ∼ 10 nm, allows investigations of events occurring at timescales on the order of ∼100 ns. Among many other advantages, decreasing λ also increases spatial resolution in electrochemical imaging, e.g., in scanning electrochemical microscopy, and allows probing of the electric double layer. This Introductory Lecture traces the evolution and driving forces behind the "λ2 ∼ Dt" steady-state approach to nanoscale electrochemistry, beginning in the late 1950s with the introduction of the rotating ring-disk electrode and twin-electrode thin-layer cells, and evolving to current-day investigations using nanoelectrodes, scanning nanocells for imaging, nanopores, and nanoparticles. The recent focus on so-called "single-entity" electrochemistry, in which individual and very short redox events are probed, is a significant departure from the steady-state approach, but provides new opportunities to probe reaction dynamics. The stochastic nature of very fast single-entity events challenges current electrochemical methods and modern electronics, as illustrated using recent experiments from the authors' laboratory.

Investigating Strength and Range of Motion of the Hip Complex in Ice Hockey Athletes.

CONTEXT: Ice hockey athletes frequently injure the hip complex via a noncontact mechanism. The authors investigated patterns of strength and range of motion (ROM) to establish major differences compared with soccer athletes. Soccer athletes were compared with ice hockey athletes due to similarities between the 2 sports with regard to the intermittent nature and high number of lower-limb injuries. OBJECTIVE: To compare the differences in ROM and strength of the hip for both the dominant (Dom) and nondominant (Ndom) limbs in ice hockey and soccer athletes. DESIGN: Case-control study. SETTING: Bilateral ROM in hip flexion in sitting (FS) and lying (FL), extension, abduction, adduction, and internal rotation (IR) and external rotation (ER) were measured using a goniometer and assessed for strength using a handheld dynamometer on both the Dom and Ndom limbs. PARTICIPANTS: 24 male, active, uninjured NCAA Division III ice hockey (16) and soccer (8) athletes. MAIN OUTCOME MEASURES: ROM and strength for hip FS, FL, extension, abduction, adduction, IR, and ER. A mixed-model ANOVA was used to investigate interactions and main effects. RESULTS: Ice hockey athletes exhibited greater hip-adduction ROM than soccer athletes in the Dom leg (both P = .002) and when both limbs were combined (P = .010). Ice hockey athletes had less ROM in ER (P = .042) than soccer athletes. Ice hockey athletes displayed less strength in adduction in their Ndom leg than in their Dom leg (P = .02), along with less adduction than soccer players in their Ndom leg (P = .40). Ice hockey athletes displayed less strength in hip adduction (P = .030), FS (P = .023) and FL (P = .030) than soccer athletes. CONCLUSIONS: The findings suggest that ice hockey athletes may present an at-risk profile for noncontact hip injuries in comparison with soccer athletes with regard to strength and ROM of the hip.

A novel gene causing a mendelian audiogenic mouse epilepsy.

Frings mice are a model of generalized epilepsy and have seizures in response to loud noises. This phenotype is due to the autosomal recessive inheritance of a single gene on mouse chromosome 13. Here we report the fine genetic and physical mapping of the locus. Sequencing of the region led to identification of a novel gene; mutant mice are homozygous for a single base pair deletion that leads to premature termination of the encoded protein. Interestingly, the mRNA levels of this gene in various tissues are so low that the cDNA has eluded detection by standard library screening approaches. Study of the MASS1 protein will lead to new insights into regulation of neuronal excitability and a new pathway through which dysfunction can lead to epilepsy.

The antiepileptic and anticancer agent, valproic acid, induces P-glycoprotein in human tumour cell lines and in rat liver.

BACKGROUND AND PURPOSE: The antiepileptic drug valproic acid, a histone deacetylase (HDAC) inhibitor, is currently being tested as an anticancer agent. However, HDAC inhibitors may interact with anticancer drugs through induction of P-glycoprotein (P-gp, MDR1) expression. In this study we assessed whether valproic acid induces P-gp function in tumour cells. We also investigated effects of valproic acid on the mRNA for P-gp and the cytochrome P450, CYP3A, in rat livers. EXPERIMENTAL APPROACH: Effects of valproic acid on P-gp were assessed in three tumour cell lines, SW620, KG1a and H4IIE. Accumulation of acetylated histone H3 in rats' livers treated for two or seven days with valproic acid was evaluated using a specific antibody. Hepatic expression of the P-gp genes, mdr1a, mdr1b and mdr2, was determined by real-time polymerase chain reaction. The effects of valproic acid on CYP3A were assessed by Northern blot analysis and CYP3A activity assays. KEY RESULTS: Valproic acid (0.5-2.0 mM) induced P-gp expression and function up to 4-fold in vitro. The effect of a series of valproic acid derivatives on P-gp expression in SW620 and KG1a cells correlated with their HDAC inhibition potencies. Treatment of rats with 1 mmol kg(-1) valproic acid for two and seven days increased hepatic histone acetylation (1.3- and 3.5-fold, respectively) and the expression of mdr1a and mdr2 (2.2-4.1-fold). Valpromide (0.5-2.0 mM) did not increase histone acetylation or P-gp expression in rat livers, but induced CYP3A expression. CONCLUSIONS: Valproic acid increased P-gp expression and function in human tumour cell lines and in rat liver. The clinical significance of this increase merits further investigation.

Effect of topiramate and dBcAMP on expression of the glutamate transporters GLAST and GLT-1 in astrocytes cultured separately, or together with neurons.

The mechanism of the antiepileptic drug topiramate is not fully understood, but interaction with the excitatory neurotransmission, e.g. glutamate receptors, is believed to be part of its anticonvulsant effect. The glutamate transporters GLAST and GLT-1 are responsible for the inactivation of glutamate as a neurotransmitter and it was therefore investigated if topiramate might affect the expression of GLAST and GLT-1 in astrocytes cultured separately or together with neurons. Since expression and membrane trafficking of glutamate transporters are affected by the protein kinase C system as well as by dBcAMP it was also investigated if these signalling pathways might play a role. In astrocyte cultures expressing mainly GLAST treatment with dBcAMP (0.25 mM) led to an increased expression of the total amount of GLAST as well as of its membrane association. The enhanced expression in the membrane was particularly pronounced for the oligomeric form of GLAST. No detectable effect on the expression of GLAST in astrocytes treated with topiramate in the presence and absence of protein kinase C activators or inhibitors was observed. Astrocytes co-cultured with neurons expressed both GLAST and GLT-1. In these cultures prolonged exposure to 30 muM topiramate (10 days) led to a statistically significant increase (P<0.025) in the membrane expression of GLAST. In case of GLT-1, culture in the presence of 30 microM topiramate for 1 and 10 days led to alterations in the total, cytoplamic and membrane expression of the oligomeric form of the transporter.

Which short-term therapy? Matching patient and method.

In recent years, numerous forms of short-term psychotherapy have been developed, without clear guidelines for choosing among them. There are three major approaches in terms of both their techniques and their criteria for patient selection. The "interpretive" method stresses the use of insight produced by a therapist's interpretations, the "existential," the maturational effect of a brief empathic encounter with the therapist, and the "corrective," the behavioral changes resulting from patient management by the therapist. The question facing a short-term therapist is how to choose a particular method for a particular patient. A framework is proposed based on developmental phases of adult life to help therapists match patient and method.

Decrease in CA3 inhibitory network activity during Theiler's virus encephalitis.

Viral infections of the central nervous system are often associated with seizures, and while patients usually recover from the infection and the seizures cease, there is an increased lifetime incidence of epilepsy. These viral infections can result in mesial temporal sclerosis, and, subsequently, a type of epilepsy that is difficult to treat. In previous work, we have shown that Theiler's murine encephalomyelitis virus (TMEV) infections in C57B/6 mice, an animal model of virus-induced epilepsy, results in changes in excitatory currents of CA3 neurons both during the acute infection and two months later, at a time when seizure thresholds are reduced and when spontaneous seizures can occur. The changes in the excitatory system differ at these two time points, suggesting different mechanisms for seizure generation. In the present paper, we examine GABAergic mediated inhibition in CA3 pyramidal cells at these two time points following TMEV infection. We found that amplitudes of sIPSCs and mIPSCs were reduced during the acute infection, but recovered at the two-month time point. These observations are consistent with previous measurements of excitatory currents suggesting different mechanisms of seizure generation during the acute infection and during chronic epilepsy.

Direct imaging of molecular transport through skin.

Scanning electrochemical microscopy (SECM) was used to image spatial variations in the molecular flux of Fe(CN)6(-4) across excised hairless and nude mouse skin. The SECM response is specific to electroactive molecules, allowing selective imaging of the flux of Fe(CN)6(-4) in multicomponent ionic solutions. Quantitative SECM image analysis demonstrated that 40% to 60% of the total Fe(CN)6(-4) flux occurred through appendages in the skin. SECM analysis of skin samples exposed to a known transport enhancer, sodium dodecylsulfate, indicated that the increase in the ion transport rate occurred exclusively in nonporous skin tissue.

3-(2-Carboxyindol-3-yl)propionic acid-based antagonists of the N-methyl-D-aspartic acid receptor associated glycine binding site.

A series of substituted 3-(2-carboxyindol-3-yl)propionic acids was synthesized and tested as antagonists for the strychnine-insensitive glycine binding site of the NMDA receptor. Chlorine, and other small electron-withdrawing substituents in the 4- and 6-positions of the indole ring, greatly enhanced binding and selectivity for the glycine site over the glutamate site of the NMDA receptor; one of the most potent compounds is 3-(4,6-dichloro-2-carboxyindol-3-yl)propionic acid (IC50 = 170 nM; greater than 2100-fold selective for glycine). The importance of a heteroatom NH and the enhancing effect of the propionic acid side chain were demonstrated and are consistent with previous results which suggest the presence of a pocket on the receptor which can accept an acidic side chain. Substitution of a sulfur at C3 led to the most potent compound 3-[(carboxymethyl)thio]-2-carboxy-4,6-dichloroindole (IC50 = 100 nM).

Aroyl(aminoacyl)pyrroles, a new class of anticonvulsant agents.

2-Aroyl-4-(omega-aminoacyl)- (4) and 4-aroyl-2-(omega-aminoacyl)pyrroles (9) represent a new, structurally novel class of anticonvulsant agents. Compounds of type 4 were prepared by Friedel-Crafts acylation of a 2-aroylpyrrole with an omega-chloroacyl chloride followed by displacement of the chloro group by a primary or secondary amine. Compounds of type 9 were prepared by Friedel-Crafts aroylation of a 2-(omega-chloroacyl)pyrrole followed by displacement by an amine. These compounds were active in the mouse and rat maximal electroshock tests but not in the mouse metrazole test. The lead compound, RWJ-37868, 2-(4-chlorobenzoyl)-4-(1-piperidinyl-acetyl)-1,3,5-trimethylpyrrole++ + (4d), showed potency and therapeutic index comparable to those of phenytoin and carbamazepine and greater than those of sodium valproate. This compound blocked bicuculline induced seizures, did not elevate seizure threshold following iv infusion of metrazole, and blocked influx of Ca2+ ions into cerebellar granule cells induced by K+ or veratridine.

Selective inhibitors of glial GABA uptake: synthesis, absolute stereochemistry, and pharmacology of the enantiomers of 3-hydroxy-4-amino-4,5,6,7-tetrahydro-1,2-benzisoxazole (exo-THPO) and analogues.

3-Methoxy-4,5,6,7-tetrahydro-1,2-benzisoxazol-4-one (20a), or the corresponding 3-ethoxy analogue (20b), and 3-chloro-4,5,6, 7-tetrahydro-1,2-benzisothiazol-4-one (51) were synthesized by regioselective chromic acid oxidation of the respective bicyclic tetrahydrobenzenes 19a,b and 50, and they were used as key intermediates for the syntheses of the target zwitterionic 3-isoxazolols 8-15 and 3-isothiazolols 16 and 17, respectively. These reaction sequences involved different reductive processes. Whereas (RS)-4-amino-3-hydroxy-4,5,6,7-tetrahydro-1,2-benzisoxazole (8, exo-THPO) was synthesized via aluminum amalgam reduction of oxime 22a or 22b, compounds 9, 11-13, and 15-17 were obtained via reductive aminations. Compound 10 was synthesized via N-ethylation of the N-Boc-protected primary amine 25. The enantiomers of 8 were obtained in high enantiomeric purities (ee >/= 99.1%) via the diastereomeric amides 32 and 33, synthesized from the primary amine 23b and (R)-alpha-methoxyphenylacetyl chloride and subsequent separation by preparative HPLC. The enantiomers of 9 were prepared analogously from the secondary amine 27. On the basis of X-ray crystallographic analyses, the configuration of oxime 22a was shown to be E and the absolute configurations of (-)-8 x HCl and (+)-9 x HBr were established to be R. The effects of the target compounds on GABA uptake mechanisms in vitro were measured using a rat brain synaptosomal preparation and primary cultures of mouse cortical neurons and glia cells (astrocytes). Whereas the classical GABA uptake inhibitor, (R)-nipecotic acid (2), nonselectively inhibits neuronal (IC(50) = 12 microM) and glial (IC(50) = 16 microM) GABA uptake and 4,5,6,7-tetrahydroisoxazolo¿4,5-cpyridin-3-ol (1, THPO) shows some selectivity for glial (IC(50) = 268 microM) versus neuronal (IC(50) = 530 microM) GABA uptake, exo-THPO (8) was shown to be more potent as an inhibitor of glial (IC(50) = 200 microM) rather than neuronal (IC(50) = 900 microM) GABA uptake. This selectivity was more pronounced for 9, which showed IC(50) values of 40 and 500 microM as an inhibitor of glial and neuronal GABA uptake, respectively. These effects of 8 and 9 proved to be enantioselective, (R)-(-)-8 and (R)-(+)-9 being the active inhibitors of both uptake systems. The selectivity of 9 as a glial GABA uptake inhibitor was largely lost by replacing the N-methyl group of 9 by an ethyl group, compound 10 being an almost equipotent inhibitor of glial (IC(50) = 280 microM) and neuronal (IC(50) = 400 microM) GABA uptake. The remaining target compounds, 11-17, were very weak or inactive as inhibitors of both uptake systems. Compounds 9-13 and 15 were shown to be essentially inactive against isoniazide-induced convulsions in mice after subcutaneous administration. The isomeric pivaloyloxymethyl derivatives of 9, compounds 43 and 44, were synthesized and tested as potential prodrugs in the isoniazide animal model. Both 43 (ED(50) = 150 micromol/kg) and 44 (ED(50) = 220 micromol/kg) showed anticonvulsant effects, and this effect of 43 was shown to reside in the (R)-(+)-enantiomer, 45 (ED(50) = 44 micromol/kg). Compound 9 also showed anticonvulsant activity when administered intracerebroventricularly (ED(50) = 59 nmol).

Effects of 4,4'-di-isothiocyano-2,2'-stilbene disulphonate on iodide uptake by primary cultures of turtle thyroid follicular cells.

Iodide uptake by primary cultures of turtle thyroid follicular cells is directly proportional to the Na+ concentration and is inversely proportional to the HCO3- concentration in culture medium, but is not affected by the Cl- concentration. Addition of 4,4'-di-isothiocyano-2,2'-stilbene disulphonate (DIDS; 10 mumol/l and higher doses) to medium containing different concentrations of Na+ (5-140 mmol/l), HCO3- (0-40 mmol/l) and Cl- (120 mmol/l) generally enhanced iodide uptake by the cultured cells; however, there was no significant effect in Na+-free and in low Cl- (90 mmol/l and less) medium. The inhibitory effects on iodide uptake of ouabain, frusemide and perchlorate were attenuated by DIDS which also antagonized the stimulatory effects on iodide uptake of TSH, although both DIDS and TSH increased the 125I- cell/medium ratio when they were given alone. At doses of 100 mumol/l and higher, DIDS lowered the intracellular pH of cultured cells when the pH of the medium was maintained at a constant level. It also increased the intracellular Cl- concentration, but had no effect on intracellular Na+ or K+. The input and specific resistances of cell membranes in cultured thyroid cells and in isolated thyroid slices increased (decreased conductance) after adding DIDS to the perfusion fluids. Both Na+/K+- and HCO3(-)-ATPase activities in homogenates of turtle thyroid tissue were inhibited by DIDS. Results from this investigation demonstrate (1) that in addition to preventing the leak of iodide from thyroid cells, DIDS may act to increase the sensitivity of the Na+-anion carrier to I- and thereby increases iodide uptake, and (2) that a HCO3(-)-Cl- exchange system is present in the thyroid cell membrane and appears to be linked to the transport of iodide into thyroid cells.

Cytokine and intracellular signaling regulation of tissue factor expression in astrocytes.

There is evidence that inflammatory cytokines such as IL-1beta, TNFalpha, and IL-6 are involved in the pathogenesis of cerebrovascular disorders including stroke. One action of cytokines that contributes to diseases in peripheral tissues is upregulation of the procoagulant receptor tissue factor (TF). In the CNS, astrocytes are the primary cells that express TF; although little is known about how TF is regulated in these cells. Experiments were performed to evaluate the effect of cytokine treatment on TF activity in primary cultures of murine cortical astrocytes and in the human astrocytoma cell line (CCF). IL-1beta treatment induced a 2.5-fold increase in TF activity in the primary astrocytes and a 3-fold induction in the astrocytoma cells. TNFalpha treatment induced a 2.5-fold increase in TF activity in both the primary astrocytes and astrocytoma cells. IL-6 upregulated TF activity 2-fold in primary astrocytes, however, it had no effect on TF activity in the astrocytoma cells. The signaling pathways regulating TF expression in these cells were examined by using staurosporine, a broad spectrum inhibitor of serine-threonine protein kinases, and by examining the effects of intermediates in the sphingomyelin signaling pathway. Staurosporine inhibited IL-1beta-induced TF activity in the primary astrocytes but did not effect IL-1beta- or TNFalpha-induced TF activity in the astrocytoma cells. TF activity in the astrocytoma cells was upregulated 1.5-fold over constitutive levels by a ceramide analogue or the enzyme sphingomyelinase, however the ceramide analogue had no effect on TF activity in the primary astrocytes. These results suggest inflammatory cytokines can upregulate TF activity in astrocytes and the astrocytoma CCF cell line although the two cell types appear to utilize different signaling pathways to mediate TF expression. Further studies will be important to more completely define the signaling regulation of TF in astrocytes since alterations in brain TF levels may play a key role in CNS pathophysiology.

Ionic dependence of adenosine uptake into cultured astrocytes.

Adenosine uptake in cultured astrocytes is dependent on various ions and energy metabolism. The Na(+)-gradient plays an important role, since nigericin, ouabain, amiloride and substitution of Na+ with choline inhibited adenosine uptake. The proton-gradient was of importance, since carbonylcyanide m-chlorophenylhydrozone (CCCP) and omeprazole also inhibited adenosine uptake. Furthermore, adenosine uptake was dependent on Cl- anion. Substitution of Cl- with isethionate, as well as DIDS or furosemide inhibited adenosine uptake. Adenosine uptake was also sensitive to Ca2+ gradient, removal of extracellular Ca2+ and calcimycin inhibited adenosine uptake. Adenosine uptake was not dependent on extracellular K+ and was not affected by valinomycin. Although, K(+)-channel openers (BRL 34195 and nicorandil) as well as the K(+)-channel antagonist, glyburide, inhibited adenosine uptake, the inhibitory effect of BRL 34915 was not antagonized by glyburide. Rotenone and 2,4-dinitrophenol also inhibited adenosine uptake. Ionic dependence and metabolic energy dependence of adenosine uptake suggest that uptake is primarily an active process.

Distinct features of seizures induced by cocaine and amphetamine analogs.

Seizure-related emergencies caused by stimulants of abuse have been increasing. To better understand the nature of these drug-induced convulsions, we characterized the seizure patterns associated with high doses of cocaine, and the amphetamine analogs, methamphetamine, methylenedioxymethamphetamine (MDMA) and 4-methylaminorex. The features of the stimulant-induced seizures were distinct and included the following: (1) the duration of convulsive activity was shortest for cocaine and longest for methamphetamine, (2) only MDMA produced a secondary clonic phase after the initial ictal event, and (3) 4-methylaminorex manifested a very steep dose-response curve. Differential preventive profiles of anticonvulsant agents on the stimulant-induced seizures also were observed. For example, cocaine-related seizures were most effectively prevented by, while methamphetamine-induced seizures were completely refractory to, phenytoin pretreatment. The only anticonvulsants which appeared to influence methamphetamine-related convulsions were diazepam and valproate. A unique feature of 4-methylaminorex was that related seizures were almost completely blocked by the calcium channel blocker, flunarizine.

Local application of cyclic AMP in the rat brain: characterization of the cardiovascular response.

Previous studies have demonstrated that central administration of dibutyryl cyclic AMP (DBcAMP) produces a dose-dependent rise in blood pressure accompanied by tachycardia. In an attempt to delineate brain sites that mediate these cardiovascular responses, DBcAMP was stereotaxically injected into local brain areas. Injections of 100 micrograms into the right lateral, third, and fourth ventricles produced pressor responses. Perfusion of the brain from the lateral ventricle to the cisterna magna with 15 micrograms/25 microliters per min induced a rise in blood pressure and significant bradycardia. The cyclic nucleotide was injected unilaterally in doses of 10, 25, and 50 micrograms into the posterior hypothalamic nucleus (PHN), anterior hypothalamic area (AHA), locus coeruleus (LC), and nucleus tractus solitarii (NTS). PHN injections induced tachycardia with minimal changes in blood pressure. Bradycardia and a depressor response were observed following injection of the 10 micrograms dose into the LC. Within the AHA, DBcAMP (10 micrograms) did not induce significant changes in cardiovascular function. Additionally, injections into the NTS initiated a biphasic depressor-pressor effect. Within these sites, cardiovascular responses to the 10 micrograms dose of DBcAMP paralleled those observed after adrenergic activation. These results strongly suggest that cyclic AMP functions as a second messenger within select central cardiovascular regulatory sites and plays an important role in cardiovascular regulation.

Studies on the central pressor activity of dibutyryl cyclic AMP.

The effects of the central administration (i.c.v.) of dibutyryl cyclic AMP (DBcAMP) on arterial blood pressure and heart rate were studied in the rat. The cyclic nucleotide produced a dose-dependent rise in blood pressure and an accompanying tachycardia. Maximal pressor effect of a single dose of DBcAMP (350 micrograms) was observed 25 min post injection and the duration of the response was 60 min. Chemical degeneration of central catecholaminergic neurons with 6-hydroxydopamine treatment abolished the pressor response to DBcAMP. Partial chemical degeneration of central serotonin pathways with 5,6-dihydroxytryptamine did not significantly alter the effect. The pressor activity of the cyclic nucleotide was attenuated by central administration of phentolamine. Spinal cord section at the C6-C7 level or peripheral chemical degeneration of catecholaminergic neurons combined with bilateral adrenalectomy abolished the pressor response to DBcAMP. It was concluded that the pressor response to i.c.v. administration of DBcAMP is mediated by central catecholaminergic pathways and is the result of an increase in efferent sympathetic outflow and release of catecholamines from the adrenal medulla.

The dihydropyridine nitrendipine inhibits [3H]MK 801 binding to mouse brain sections.

The L-type Ca2+ channel antagonist nitrendipine inhibits N-methyl-D-aspartate (NMDA)-activated Ca2+ flux into cerebellar granule cells, and [3H]dibenzocyclohepteneimine ([3H]MK 801) binding to mouse cerebral cortical and hippocampal membranes. To further study this interaction between nitrendipine and NMDA-activated channels, the effects of several L-channel active agents on [3H]MK 801 binding to mouse brain were investigated in an autoradiographic assay. Serial slide-mounted sagittal sections of mouse brain were labeled with [3H]MK 801 in the presence of varying concentrations of the L-channel active agents nitrendipine, nimodipine, nifedipine, Bay K 8644, and verapami. Nitrendipine potently displaced 2 nM [3H]MK 801 binding to mouse brain sections (IC50 = 89.8 nM). Dose-dependent inhibition of [3H]MK 801 binding by nitrendipine was demonstrated in most brain regions examined. 10(-5) M and 10(-8) M concentrations of the other dihydropyridines studied, and of verapamil, were without effect. The data supports a unique, direct interaction between nitrendipine and the NMDA-activated ion channel.

Anticonvulsant activity of the gamma-aminobutyric acid uptake inhibitor N-4,4-diphenyl-3-butenyl-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol .

The N-4,4-diphenyl-3-butenyl derivative of the glial selective gamma-aminobutyric acid (GABA) uptake inhibitor 4,5,6,7-tetrahydroisoxazolo [4,5-c]pyridin-3-ol (N-DPB-THPO), was tested for its ability to block sound-induced seizures in the audiogenic seizure-susceptible Frings mouse model of epilepsy. Following intracerebroventricular (i.c.v.) administration, N-DPB-THPO blocked tonic hindlimb extension in a dose- and time-dependent manner. At the doses tested no gross behavioral effects were noted.

Pharmacological characterization of MDL 105,519, an NMDA receptor glycine site antagonist.

MDL 105,519, (E)-3-(2-phenyl-2-carboxyethenyl)-4,6-dichloro-1 H-indole-2-carboxylic acid, is a potent and selective inhibitor of [3H]glycine binding to the NMDA receptor. MDL 105,519 inhibits NMDA (N-methyl-D-aspartate)-dependent responses including elevations of [3H]N-[1,(2-thienyl)cyclohexyl]-piperidine ([3H]TCP) binding in brain membranes, cyclic GMP accumulation in brain slices, and alterations in cytosolic CA2+ and NA(+)-CA2+ currents in cultured neurons. Inhibition was non-competitive with respect to NMDA and could be nullified with D-serine. Intravenously administered MDL 105,519 prevented harmaline-stimulated increases in cerebellar cyclic GMP content, providing biochemical evidence of NMDA receptor antagonism in vivo. This antagonism was associated with anticonvulsant activity in genetically based, chemically induced, and electrically mediated seizure models. Anxiolytic activity was observed in the rat separation-induced vocalization model, but muscle-relaxant activity was apparent at lower doses. Higher doses impair rotorod performance, but were without effect on mesolimbic dopamine turnover or prepulse inhibition of the startle reflex. This pattern of activities differentiates this compound from (5R,10S)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) and indicates a lower psychotomimetic risk.