Design of an irreversible affinity ligand for the phencyclidine recognition site on N-methyl-D-aspartate-type glutamate receptors.

A series of 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP) analogs were synthesized with the aim of developing a potent ligand for the N-methyl-D-aspartate glutamate receptor subtype. The piperidine moiety of TCP was substituted at the nitrogen position with aliphatic chains of different length or with various polar groups. A correlation between the decrease in the potency of displacement of [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-im ine maleate (MK-801) binding from bovine cortex membranes and the increase of length or polarity of the aliphatic chain was observed.

NMDA receptor-mediated arachidonic acid release in neurons: role in signal transduction and pathological aspects.

The N-methyl-D-aspartate (NMDA)-sensitive subtype of glutamate receptor, which gates Ca(2+)-permeable ion channels, is known for its role in learning and memory formation, in the induction of long-term potentiation, and also in seizure activity and neurotoxicity. In primary cultures of cerebellar neurons, agonists of NMDA receptors induce a dose-dependent release of [3H]arachidonic acid ([3H]AA), which is potentiated by activation of the glycine-positive modulatory site and inhibited by NMDA receptor antagonists. NMDA receptor-induced [3H]AA release is inhibited by quinacrine and partially depends on the presence of extracellular calcium.

Glutamate receptor agonists stimulate nitric oxide synthase in primary cultures of cerebellar granule cells.

The glutamate receptor agonist N-methyl-D-aspartate (NMDA) stimulated a rapid, extracellular Ca(2+)-dependent conversion of [3H]arginine to [3H]citrulline in primary cultures of cerebellar granule cells, indicating receptor-mediated activation of nitric oxide (NO) synthase. The NMDA-induced formation of [3H]citrulline reached a plateau within 10 min. Subsequent addition of unlabeled L-arginine resulted in the disappearance of 3H from the citrulline pool, indicating a persistent activation of NO synthase after NMDA receptor stimulation.

Dopaminergic regulation of cholecystokinin mRNA content in rat striatum.

The nigrostriatal dopaminergic activity was pharmacologically changed to assess whether dopamine (DA) regulates cholecystokinin (CCK) mRNA steady state in rat striatum. Cocaine and benztropine, two dopaminergic agonists known to induce DA release and to block its re-uptake, produced a time dependent increase in CCK mRNA content in rat striatum. A significant increase in striatal CCK mRNA was observed 8 h after a single injection of cocaine (15 mg/kg, i.

Pharmacological characterization of regulation of phosphoinositide metabolism by recombinant 5-HT2 receptors of the rat.

Transfection of 5-HT2 receptor cDNA in 293 cells induced the expression of a protein binding domain, exhibiting the classical 5-HT2 receptor transduction mechanism. Both [3H]DOB and [3H]spiperone high affinity binding sites were present in membranes of sense but not of antisense, 5-HT2 receptor cDNA transfected cells. Addition of 1 microM 5-HT induced a time-dependent increase of phosphoinositide (PI) metabolism in sense but not in antisense, 5-HT2 receptor cDNA transfected cells.

Role of DBI in brain and its posttranslational processing products in normal and abnormal behavior.

Because diazepam binding inhibitor (DBI) and its processing products coexist with gamma-aminobutyric acid (GABA) in several axon terminals, DBI immunoreactivity was measured in the cerebrospinal fluid (CSF) of individuals suffering from various neuropsychiatric disorders, that are believe to be associated with abnormalities of GABAergic transmission. Increased amounts of DBI-like immunoreactivity were found in the CSF of patients suffering from severe depression with a severe anxiety component (Barbaccia, Costa, Ferrero, Guidotti, Roy, Sunderland, Pickar, Paul and Goodwin, 1986). Moreover, the amount of DBI and its processing products was found to be increased in the CSF of patients with hepatic encephalopathy (HE) (Rothstein, McKhann, Guarneri, Barbaccia, Guidotti and Costa, 1989; Guarneri, Berkovich, Guidotti and Costa, 1990).

"Prolegomena" to the biology of the diazepam binding inhibitor (DBI).

The historical background and the present views on the actions of DBI on GABAergic transmission are summarized in these introductory remarks.

Inhibition of glutamate-induced cell death by sodium nitroprusside is not mediated by nitric oxide.

Pretreatment of primary cultures of cerebellar granule cells with sodium nitroprusside (SNP) protected these neurons from delayed death induced by glutamate and N-methyl-D-aspartate (NMDA). This neuroprotective effect was not mimicked by S-nitroso-N-acetylpenicillamine (SNAP) which like SNP stimulates guanylate cyclase via a nitric oxide (NO) related mechanism. In contrast, neuroprotection was achieved with potassium ferrocyanide, a compound structurally related to SNP, but devoid of NO.

Glutamate neurotoxicity is independent of calpain I inhibition in primary cultures of cerebellar granule cells.

Glutamate-induced neurotoxicity and calpain activity were studied in primary cultures of rat cerebellar granule neurons and glial cells. Calpain activation, as monitored by quantitative immunoblotting of spectrin, required micromolar concentrations of Ca2+ in neuronal homogenates (calpain I) and millimolar Ca2+ concentrations in glial homogenates (calpain II). Glutamate-induced toxicity and calpain activation were observed in neuronal, but not in glial, cultures.

Nonselective inhibition by antisense oligonucleotides of cytosine arabinoside action.

Antisense oligonucleotides can be used in cell cultures to inhibit biosynthesis of neurotransmitter receptors. Hence, they operate as highly specific pharmacological antagonists. In obtaining a pure neuronal primary culture the suppression of non-neuronal cell proliferation is required; usually 1-beta-D-arabinofuranosylcytosine (AraC) is used.

gamma-Aminobutyric acid-B receptors inhibit glutamate release from cerebellar granule cells: consequences of inhibiting cyclic AMP formation and calcium influx.

In cerebellar granule cells, baclofen acted with micromolar concentrations at proposed gamma-aminobutyric acid-B receptors to inhibit the formation of cyclic AMP and depolarization-induced release of glutamate. Nanomolar concentrations of baclofen inhibited depolarization-induced influx of calcium. All three responses to baclofen were attenuated after pertussis toxin pretreatment of cell cultures.

Mechanism of nerve growth factor mRNA regulation by interleukin-1 and basic fibroblast growth factor in primary cultures of rat astrocytes.

Neonatal rat cortical astrocytes in primary culture synthesize and secrete nerve growth factor (NGF). Interleukin-1 beta(IL-1) and basic fibroblast growth factor (bFGF) treatment of astrocytes increased NGF mRNA content by about 2-fold. The effect of these two factors was specific, because other growth factors, such as tumor necrosis factor-alpha, insulin-like growth factor-1, and epidermal growth factor, failed to change NGF mRNA content.

Regulation of diazepam binding inhibitor in rat adrenal gland by adrenocorticotropin.

Diazepam binding inhibitor (DBI) is a 9-kDa polypeptide that was initially isolated from rat brain and subsequently found to be present in several peripheral tissues. DBI is particularly abundant in steroidogenic tissues, such as the adrenal glands and testes, which also contain a high concentration of peripheral/mitochondrial benzodiazepine receptors (MBRs). Because occupancy of adrenal MBRs with DBI results in increased steroidogenesis, we have investigated the relation between ACTH, DBI, and the MBR in the rat adrenal glands.

Peripheral-type benzodiazepine receptors: a second site of action for benzodiazepines.

Benzodiazepines are among the most widely used therapeutic drugs because of their sedative and anxiolytic effects mediated through modulation of GABAA receptors. Another recognition site for these drugs, termed the peripheral-type (or mitochondrial) benzodiazepine receptor, is much more prevalent throughout the body for which a physiologic and pharmacologic role has just been found. This drug receptor plays a central role in the regulation of steroidogenesis by mediating the rate-limiting step in this biosynthetic pathway, which is transport of cholesterol to inner mitochondrial membranes.

The preferential antagonism of pentylenetetrazole proconflict responses differentiates a class of anxiolytic benzodiazepines with potential antipanic action.

With the use of the shock-induced suppression of water drinking in thirsty rats (Vogel's conflict paradigm) and the pentylenetetrazole-enhanced shock-induced suppression of drinking (proconflict paradigm) as animal models to test anxiolytic and antipanic agents, it was possible to distinguish two major classes of benzodiazepines (BZDs) and congeners on the basis of their antiproconflict index (ratio of anticonflict/antiproconflict potencies). Thus, typical low potency BZDs and congeners (diazepam, midazolam, zolpidem, alpidem) with anxiolytic/hypnotic properties have a low antiproconflict index (close to 1), whereas typical high potency BZDs (clonazepam, alprazolam, bretazenil) with reported antipanic properties have an antiproconflict index approximately 10-fold higher. The anticonflict and antiproconflict actions of BZDs with low or high antiproconflict indices are blocked by flumazenil but are potentiated differentially by the gamma-aminobutyric acid (GABA) reuptake blocker 1-2-[bis(trifluoromethyl)-phenyl]-methoxyethyl-1,2,5,6-tetrahydro-3- pyridine-carboxylic acid.

Pretreatment of cerebellar granule cells with concanavalin A potentiates quisqualate-stimulated phosphoinositide hydrolysis.

The hydrolysis of phosphoinositides (PI) elicited in cerebellar granule cell cultures by agonists of metabolotropic glutamate receptors, glutmate and quisqualate, was enhanced when the cells were pretreated with concanavalin A (Con-A). A similar effect was produced by wheat germ agglutinin, but not by several other lectins tested. Con-A produced a dose-dependent effect (EC50 = 3 microM) and increased the efficacy but not the potency of the agonists.

Influence of recombinant gamma-aminobutyric acid-A receptor subunit composition on the action of allosteric modulators of gamma-aminobutyric acid-gated Cl- currents.

gamma-Aminobutyric acid (GABA)-activated Cl- currents in neonatal rat cortical neurons and in cultured cells engineered for the expression of specific molecular forms of the GABAA receptor alpha, beta, and gamma subunits, were recorded with the patch-clamp technique in the whole-cell configuration. The effects of various allosteric modulators of GABAA receptors were determined. Diazepam and clonazepam showed greater efficacy as positive modulators of GABA-elicited currents in alpha 2 beta 1 gamma 2 or alpha 3 beta 1 gamma 2 receptors than in alpha 1 beta 1 gamma 2 or alpha 5 beta 1 gamma 2 receptors or in cortical neurons.

Glutamate receptor subtypes mediate excitatory synaptic currents of dopamine neurons in midbrain slices.

Although dopamine (DA)-containing neurons participate in a number of important cerebral functions, the physiology of their synaptic connections is poorly understood. By using whole-cell patch-clamp recording in thin slices of rat mesencephalon, we have investigated the biophysical properties of synaptic events and the nature of neurotransmitter(s) and receptors involved in the synaptic input to DA neurons in substantia nigra. The histological and electrophysiological characteristics of these cells were consistent with those described by recent in vivo and in vitro studies, thus allowing their unequivocal identification.

The 5-HT2 receptor in brain: recent biochemical and molecular biological developments and new perspectives in its regulation.

Radioligand binding as well as molecular biological studies revealed an heterogeneity of serotonin (5-HT) receptors in the central nervous system. The early availability of specific antagonists for the serotonin-2 (5-HT2) receptor subtype (spiperone, ketanserin and ritanserin represented an important step towards the biochemical, physiological and, more recently, molecular characterization of 5-HT2 receptors in brain. Though they are unevenly distributed in different brain areas, they are highly expressed in the frontal cortex.

Chronic treatment with scopolamine and physostigmine changes nerve growth factor (NGF) receptor density and NGF content in rat brain.

Nerve growth factor (NGF) and NGF receptors were measured in cortex and hippocampus of rats treated with drugs affecting cholinergic neurotransmission. High (Kd = 0.045 nM) and low (Kd = 21 nM) affinity 125I-NGF binding sites were present in both cortical and hippocampal membranes with hippocampus containing higher numbers of both sites than cortex.