Loss of Inositol Phospholipids in Epididymal Sperm Following Exposure of Mice to Long-Term Feeding of Organophosphates

Abstract: The action of central and peripheral type benzodiazepine ligands on growth hormone, luteinizing hormone and follicle stimulating hormone levels in serum were studied in male rats. Graded doses of Ro 5-4864, that binds to the peripheral type benzodiazepine receptors, clonazepam, a fairly pure central type agonist and diazepam, a mixed-type agonist, were given intraperitoneally. Also a benzodiazepine partial inverse agonist, FG 7142, was investigated. Clonazepam increased growth hormone levels at 0.2 mg/kg while higher doses were not active. Diazepam (5-25 mg/kg) was not effective. FG 7142 (15 mg/kg) and Ro 5-4864 (25 mg/kg) decreased growth hormone levels. Flumazenil, a central-type antagonist, reversed at least partially the effects of clonazepam and FG 7142, suggesting an effect through GABA-benzodiazepine complex. Elevation of growth hormone could be associated with anxiolysis and decrease of growth hormone with enhanced anxiety. Clonazepam (0.2-5 mg/kg) and diazepam (5-25 mg/kg) increased luteinizing hormone concentrations, but only the effects of 1 mg/kg of clonazepam and 5 mg/kg of diazepam reached statistical significance. Even FG 7142 caused a modest increase of luteinizing hormone at 5 mg/kg, but Ro 5-4864 rather decreased luteinizing hormone, although not significantly. Flumazenil (25 mg/kg) antagonized partially the effects of diazepam and clonazepam. Effects of Ro 5-4864 and FG 7142 were not modified by flumazenil or PK 11195, a peripheral-type mixed antagonist/agonist. Luteinizing hormone stimulation by benzodiazepine ligands may be a pituitary action while inhibition could be caused by the activation of the central GABAergic system. Serum follicle stimulating hormone levels were not significantly altered by central or peripheral type benzodiazepine agonists or antagonists.     

Involvement of the "peripheral" benzodiazepine receptor type (omega 3) in the tolerance to the electroencephalographic effects of benzodiazepines in rats: comparison of diazepam and clonazepam

Rapid tolerance to the sedative effect of large doses of diazepam (10 mg/kg IV), but not of large doses of clonazepam (2 mg/kg IV) occurs in rats after 5 days of treatment on a once-a-day regimen. Electroencephalographic (EEG) studies show that such behavioral tolerance is associated with a decreased induction of spindle bursts and with an increased induction of 20-30 Hz waves (beta-like activity). Administration of clonazepam plus the agonist of the "peripheral" benzodiazepine receptor type (omega 3) Ro 5-4864 (4 mg/kg IV) for 5 days induces signs of behavioral and EEG tolerance to sedative effects of the benzodiazepine agonist. In animals treated for 5 days with diazepam plus the omega 3 antagonist PK 11195 (5 mg/kg IV), no signs of EEG and behavioral tolerance are observed. These results suggest that omega 3 type activation influences the development of rapid tolerance to the sedative effect of diazepam in rats.     

Diazepam and desmethyldiazepam differ in their affinities and efficacies at 'central' and 'peripheral' benzodiazepine receptors

The in-vitro binding characteristics of three different ligands ([ 3H]Ro 15-1788, [3H]Ro 5-4864 and [3H]flunitrazepam) and the structural requirements for binding to 'central' and 'peripheral' benzodiazepine receptors have been evaluated in rat cerebral cortex, cerebellum and adrenal glands. [3H]Ro 15-1788 binding was detectable only in the brain. Clonazepam was the most potent inhibitor followed by diazepam and desmethyldiazepam, which showed the same affinity, and by premazepam; Ro 5-4864 did not show appreciable affinity. The same pattern was seen for [3H] flunitrazepam binding in brain areas while in adrenal gland the inhibition pattern was exactly superimposable on that with [3H]Ro 5-4864 in all the areas considered (Ro 5-4864 greater than diazepam greater than desmethyldiazepam greater than clonazepam greater than premazepam). These data confirm and extend previous reports. A methyl group in position 1 enhances the affinity for peripheral benzodiazepine binding sites which are labelled in the adrenal gland by [3H]Ro 5-4864 and [3H]flunitrazepam; in brain areas, [3H]flunitrazepam, like [3H]Ro 15-1788, selectively labels central binding sites. Methylation in position 1 did not change the affinity for these sites. Desmethyldiazepam is less active than diazepam as an anticonvulsant and in other tests. In-vivo experiments were therefore carried out to assess the 'intrinsic activity' of desmethyldiazepam: it appeared that this compound acts as a partial agonist at central benzodiazepine receptors.     

Clonazepam-induced hyperphagia in nondeprived rats: tests of pharmacological specificity with Ro5-4864, Ro5-3663, Ro15-1788 and CGS 9896

Nondeprived male rats were familiarised with daily 60 min access to a highly palatable diet, consisting of powdered rat diet, sweetened condensed milk and water. Clonazepam (0.625-5.0 mg/kg, IP) produced a substantial increase in food consumption within the first 30 min of access. The increase was similar across all dose conditions, suggesting that a maximal effect may have been achieved with a dose as small as 0.625 mg/kg. The hyperphagia induced by clonazepam was reversed by the benzodiazepine receptor antagonist, Ro15-1788 (5.0-20.0 mg/kg), indicating that the effect was benzodiazepine receptor-mediated. Treatments with the peripheral-type benzodiazepine agonist, Ro5-4864, did not induce a hyperphagic response. Instead, food consumption was significantly depressed following the administration of Ro5-4864 at 20 and 40 mg/kg, IP. A comparison of the clonazepam and Ro5-4864 data suggests that benzodiazepine-induced hyperphagia is mediated by central-type benzodiazepine binding sites. The pyrazoloquinoline, CGS 9896, binds with high affinity to benzodiazepine sites and has recently been described as a nonsedating anxiolytic. CGS 9896 (2.5-20.0 mg/kg, administered either IP or PO) did not affect consumption of the highly palatable diet. In consequence, anxiolytic and hyperphagic effects of drug actions at benzodiazepine receptors may be dissociated in the case of this compound. The atypical 1,4-benzodiazepine, Ro5-3663, a GABA antagonist which may act at the picrotoxinin site, produced a dose-related reduction in food consumption. Comparison with the results for Ro5-4864 rules out an interpretation for the anorexia in terms of anxiogenic effects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential effects of anxiogenic central and peripheral benzodiazepine receptor ligands in tests of learning and memory

Previous research has demonstrated that low doses of anxiogenic central benzodiazepine receptor (CBR) ligands, the beta-carbolines, improve performance in various learning and memory tests in animals if administered prior to training. The present experiments compared the effect of a beta-carboline (FG 7142) with that of a pharmacologically distinct anxiogenic compound, a peripheral benzodiazepine receptor (PBR) ligand, 4-chlorodiazepam (Ro5-4864), in two tests of learning and memory in rats. As expected, FG 7142 significantly improved performance in a passive avoidance test. Ro5-4864 was without effect. In a shuttlebox escape test, Ro5-4864 significantly impaired performance while FG 7142 had no effect. The effect of Ro5-4864 was antagonized by the specific peripheral benzodiazepine receptor antagonist, PK 11195. These results indicate that the differential impact of CBR and PBR anxiogenic ligands on performance in aversively-motivated learning tests may be a reflection of their distinct pharmacologies.     

The role of central- and peripheral-type benzodiazepine receptors in anxiolytic-agent augmentation of NaCl solution intake: effects of clonazepam and Ro 5-4864

Two 1,4 benzodiazepines bind preferentially to the central- and peripheral-type benzodiazepine receptor in the brain, clonazepam and Ro 5-4864, respectively. They were administered to rats to determine if the relation between known anxiolytic action and efficacy in augmenting NaCl solution ingestion in rehydrating rats would remain the case for these prototypic agents. Clonazepam (0.062-32.0 mg/kg, PO) was highly potent and efficacious and increased 1.5% NaCl solution intake in a dose-related fashion. Water intake could also be increased, but to a relatively minor degree. Ro 5-4864 (4-8 mg/kg, IP) did not affect 1.5% NaCl solution ingestion, nor did this dose range suppress the augmenting effect of clonazepam (0.5-2.0 mg/kg, PO) on the solution intake. Since clonazepam does, and Ro 5-4864 does not, possess punishment-attenuation properties in other tests, drug augmentation of NaCl solution ingestion by rehydrating rats continues to correlate well with known anxiolytic action.     

Repeated administration of diazepam reduces [3H]Ro 5-4864 binding in cerebral cortex of rats.

Binding of [3H]Ro 5-4864 to mitochondrial membrane preparations of rat cerebral cortex was measured after repeated (5 days) IV administration of diazepam (10 mg/kg daily) and clonazepam (2.5 mg/kg daily). The B(max) value for [3H]Ro 5-4864 was significantly reduced in rats treated with diazepam (-49%) but not in those treated with clonazepam. These findings suggest the involvement of peripheral-type binding sites in the development of rapid tolerance to the sedative effects of benzodiazepines. A downregulation of [3H]Ro 5-4864 (-65%) was also observed after repeated administration of Ro 5-4864 (4 mg/kg daily), thus confirming that this compound behaves as an agonist at its own recognition sites.     

Diminution by benzodiazepines of the chronotropic responses to noradrenaline in rat isolated atria

The effects of various benzodiazepines on chronotropic responses were assayed in spontaneously beating rat isolated atria. The increases in atrial rate obtained from concentration-response curves to noradrenaline were reduced dose dependently by both the peripheral agonist, Ro 5-4864 5 and 10 microM, and the mixed agonist, diazepam 5, 10 and 50 microM, but not by the central benzodiazepine agonist, clonazepam 10 and 30 microM. The inhibitory effects of the benzodiazepines on the atrial responses to noradrenaline were not counteracted by either the peripheral benzodiazepine antagonist, PK 11195 10 microM, or the central benzodiazepine antagonist, Ro 15-1788 10 and 100 microM. Both 10 microM Ro 5-4864 and 10 microM diazepam also reduced the increases in atrial rate produced by either the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, or the adenylate cyclase activator, forskolin. On the contrary, diazepam and Ro 5-4864 did not modify the chronotropic responses of the atria either to direct exposure to CaCl2 or to the calcium agonist, BAY K 8644. The increases in the intracellular levels of cAMP induced by noradrenaline were not modified by Ro 5-4864 and were even increased by 50% in the presence of diazepam. It is concluded that benzodiazepines probably reduce the chronotropic responses to noradrenaline in rat isolated atria through the interaction with the cAMP-linked chain of events that follows the activation of beta-adrenoceptors.     

Discriminative stimulus properties of β-carbolines characterized as agonists and inverse agonists at central benzodiazepine receptors

The discriminative stimulus properties of three -carboline derivatives were studied in three groups of rats trained, respectively, to discriminate diazepam (2.5 mg/kg IP), chlordiazepoxide (CDP, 5 mg/kg IP) or pentylenetetrazol (PTZ, 15 mg/kg IP) from saline in standard procedures employing two-lever operant chambers. Two -carbolines, ZK 91296 and ZK 93423, substituted for the benzodiazepines in both CDP- and diazepam-trained rats. The neutral benzodiazepine antagonist Ro 15-1788 blocked the diazepam discriminative stimulus and the ability of ZK 91296 to substitute for diazepam. A third -carboline, FG 7142, was not identified as benzodiazepine-like in generalization tests in either diazepam- or CDP-trained rats, but when administered together with CDP antagonized the benzodiazepine discriminative stimulus. In rats trained to discriminate PTZ from saline (a discrimination which is thought to depend on the anxiogenic properties of PTZ) the PTZ cue was antagonized by diazepam and ZK 93423, and partially antagonized by ZK 91296. The PTZ cue generalized to FG 7142 and this generalization was partially antagonized by Ro 15-1788. These results suggest that the three -carbolines provide more than one kind of discriminative stimulus, consistent with the classification of ZK 93423 as an agonist at central benzodiazepine receptors, with ZK 91 296 as a partial agonist, and with FG 7142 as an inverse agonist. Pharmacologically, ZK 93 423 and ZK 91 296 may exhibit anxiolytic qualities, whereas FG 7142 produces anxiogenic effects.     

Pro- and anti-convulsant drug effects in combination with the convulsant benzodiazepine Ro 5-4864

The effects of several compounds believed to act at the GABA-benzodiazepine receptor complex and which have anticonvulsant or proconvulsant properties when administered in combination with picrotoxin and pentetrazol (leptazol, pentylenetetrazole) were investigated in combination with the convulsant benzodiazepine Ro 5-4864. Tracazolate (25-100 mg kg-1) failed to affect convulsions induced by Ro 5-4864; however, they were prevented by treatment with CL 218,872 (20 mg kg-1). Compounds having proconvulsant activity in combination with a subthreshold dose of Ro 5-4864 were: CL 218,872 (5 mg kg-1), and CGS 8216 (20 mg kg-1) and FG 7142 (40 mg kg-1), two compounds characterized as 'inverse agonists' at benzodiazepine receptors. The phenylquinolines PK 8165 and PK 9084, originally believed to have anxiolytic properties, had no significant effect in combination with Ro 5-4864 (25-100 mg kg-1). The convulsant profile of Ro 5-4864 is compared with that of picrotoxin and pentetrazol.     

Ro 15-4513, like anxiogenic beta-carbolines, increases dopamine metabolism in the prefrontal cortex of the rat

The effects of Ro 15-4513, FG 7142 and beta-CCM on the activity of the mesocortical dopaminergic system were examined by measuring the changes in the content of the principal dopamine (DA) metabolite, dihydroxyphenylacetic acid (DOPAC) in the prefrontal cortex of the rat. Ro 15-4513 increased the DOPAC content in the prefrontal cortex in a dose-dependent manner (5-40 mg/kg i.p.) but had no effect on DA concentrations. A similar increase in DOPAC content was induced by FG 7142 (40 mg/kg i.p.) and beta-CCM (8 mg/kg s.c.), two beta-carboline derivatives that interact with benzodiazepine recognition sites as partial inverse agonists. These effects of Ro 15-4513, FG 7142 and beta-CCM on DA metabolism in the prefrontal cortex are mediated via benzodiazepine recognition sites, since they were prevented by the administration of the benzodiazepine antagonists Ro 15-1788 and ZK 93426. These data indicate that Ro 15-4513 is an inverse agonist at benzodiazepine recognition sites.     

Strain differences in sensitivity to the hypothermic effects of benzodiazepine receptor ligands in mice

The hypothermic effects of intraperitoneal (IP) administration of the full benzodiazepine agonist lop razolam (1, 10 mg/kg); the partial agonist Ro 17-1812 (1, 10 mg/kg); the benzodiazepine receptor antagonist flumazenil (10, 20 mg/kg); the benzodiazepine inverse agonists Ro 15-4513 (1, 3, 10 mg/kg) and Ro 19-4603 (0.03, 0.1, 0.3 mg/kg) and the-carboline inverse agonists FG 7142 (10, 30 mg/kg) and DMCM (1, 3, 10 mg/kg) were investigated in three strains of mice. TO mice were less sensitive than CBA/cA and DBA/2 mice, since only loprazolam and the partial and full-carboline inverse agonists FG 7142 and DMCM lowered body temperature in these animals. CBA/cA mice were particularly sensitive to the hypothermic effects of loprazolam and Ro 17-1812, and also responded to the-carboline but not the benzo diazepine inverse agonists. In contrast, DBA/2 mice responded with moderate hypothermia to loprazolam, Ro 17-1812, and to the partial inverse agonist Ro 15-4513, and exhibited marked hypothermia in response to the more efficacious benzodiazepine inverse agonist Ro 19-4603 and to FG 7142 and DMCM. Flumazenil did not alter body temperature. DBA/2 mice were also more sensitive to the convulsant activity of inverse agonists than TO mice. CBA/cA mice exhibited enhanced sensitivity to the convulsant, but not the hypothermic, effects of Ro 19-4603, showing dissociation of these responses. The mechanisms underlying the genetic differences in sensitivity of mice to the hypothermic and convulsant action of the different ligands are unknown and warrant further investigation.     

"Central" and "peripheral" benzodiazepines and kinetics of lindane-induced toxicity

Because hypothermia and anorexia were previously found to be more sensitive indices of the effects of lindane than were convulsions, these endpoints were used to quantify the ability of benzodiazepines (BDs) and phenytoin either to ameliorate or exacerbate the toxicity of lindane in the rat. After administration of lindane (40 or 50 mg/kg) in oil per os, toxicity was counteracted by phenytoin and the "central" BD agonists diazepam and clonazepam, but was worsened by Ro 5-4864 a "peripheral" BD agonist. Clonazepam and diazepam were each more effective in counteracting lindane-induced anorexia than in stimulating food intake, presumably because the animals had been fasted and probably even controls ate maximally when food was presented. Diazepam alone (3 injections in 1 day) produced withdrawal-induced decreased food intake the following day. Clonazepam and diazepam alone each transiently decreased colonic temperature, yet effectively blocked the more severe hypothermia produced by lindane. Ro 5-4864 by itself did not produce any measurable effects, yet exacerbated all of the effects, including lethal effects, of lindane. The present findings are compatible with other evidence that lindane and Ro 5-4864 act at the picrotoxinin receptor of the GABAA-activated chloride channel and that systemic administration of agents acting at this site may produce a constellation of effects, including seizures, hypothermia and anorexia.     

Benzodiazepines inhibit neutrophil chemotaxis and superoxide production in a stimulus dependent manner; PK-11195 antagonizes these effects.

Diazepam, which binds both central (neuronal) and peripheral (non-neuronal) benzodiazepine binding sites, and Ro5-4864, a ligand selective for benzodiazepine peripheral binding sites (PBS), both inhibited the FMLP induced chemotaxis in human neutrophils at concentrations as low as 10(-8) M. A selective peripheral benzodiazepine antagonist, PK-11195 (10(-5) M), partially reversed the benzodiazepine inhibition of chemotaxis. Diazepam also inhibited the superoxide production induced by FMLP, NaF, and A23187, but not that induced by PMA whose stimulant action was insensitive even to 10(-4) M diazepam. The FMLP-induced superoxide production was most sensitive to diazepam inhibition (ID50 = 2.25 x 10(-6) M diazepam); the effect of NaF was slightly less sensitive (ID50 = 1.34 x 10(-5) M diazepam); and the effect of A23187 was least sensitive as it was suppressed only at 10(-4) M diazepam concentrations. Like diazepam, Ro5-4864 inhibited the FMLP-induced superoxide production, and PK-11195 (10(-5) M) significantly antagonized both diazepam and Ro5-4864 inhibition. Binding studies showed the presence of a saturable benzodiazepine 'peripheral' type binding site (PBS) on human neutrophils with a Kd of 1.2 +/- 0.06 x 10(-8) M (+/- SEM), and a Bmax of 1028 +/- 86.2 fmol/10(6) cells (+/- SEM) for [3H]Ro5-4864; the binding was displaceable by PK-11195, Ro5-4864 and diazepam but not by clonazepam.     

Enhancement by benzodiazepines of the inhibitory effect of adenosine on skeletal neuromuscular transmission.

1. Interactions of benzodiazepines with adenosine on the neuromuscular transmission were studied in mouse diaphragm preparations. 2. In tubocurarine (0.6-0.8 microM)-partially paralyzed preparations, diazepam (35 microM) and Ro 5-4864 (3-30 microM), a peripheral type benzodiazepine receptor agonist, potentiated the inhibitory effect of adenosine on indirect twitch responses. 3. The central type receptor agonist, clonazepam did not affect the inhibitory effect of adenosine. 4. The peripheral benzodiazepine receptor antagonist, PK11195 (1-10 microM) attenuated the adenosine inhibition and antagonized the potentiation by Ro 5-4864. 5. Ro 5-4864 failed to enhance further the inhibitory effect of adenosine in the presence of dipyridamole, an adenosine uptake inhibitor that also potentiated adenosine inhibition. 6. Neither Ro 5-4864 nor PK 11195 affected the inhibition produced by a stable adenosine analogue, 2-chloroadenosine, which is not a substrate for the adenosine uptake system. 7. Ro 5-4864 did not affect endplate potentials (e.p.ps) in the absence of adenosine, but reduced the amplitude of e.p.ps in the presence of adenosine without affecting miniature e.p.ps. 8. It is suggested that benzodiazepines potentiate the adenosine-effected presynaptic inhibition of neuromuscular transmission by an inhibition of adenosine uptake through activation of peripheral type benzodiazepine receptors.     

Peripheral benzodiazepine binding sites in Nb 2 node lymphoma cells: effects on prolactin-stimulated proliferation and ornithine decarboxylase activity

[3H]Ro 5-4864 binds to Nb 2 node lymphoma cells in a specific saturable and reversible fashion. Scatchard analysis of specific binding data reveals a single, homogeneous class of whole cell binding sites with a Kd of 3.94 +/- 0.22 nM and a Bmax value of 155 +/- 11 fmol (Ro 5-4864 bound)/2 x 10(6) cells. Ro 5-4864, a reported peripheral benzodiazepine receptor agonist both inhibits (10(-6) M) and potentiates (10(-9) M) the mitogenic action of prolactin on the Nb 2 node lymphoma cells. Interestingly, PK 11195, an antagonist, potentiates (10(-9) M) the mitogenic activity of prolactin in these cells. The actions of both Ro 5-4864 and PK 11195 seem to be mediated through a common receptor type since a 10(-6) M concentration of either agent will block the others potentiating action. Furthermore, the simultaneous addition of a 10(-9) M concentration of Ro 5-4864 and PK 11195 does not further increase the effect on prolactin stimulated mitogenesis. Clonazepam, a central benzodiazepine receptor agonist has no effect on prolactin-stimulated mitogenesis in this system. These data suggest that the Nb 2 node lymphoma cells possess a peripheral-type benzodiazepine receptor. In these cells, this receptor seems to serve the function of modulating the ability of the growth factor, prolactin to initiate the mitogenic process. These studies also suggest that Ro 5-4864 is functioning as a partial agonist rather than a 'pure' agonist for the peripheral benzodiazepine receptor in this system.     

Reduction of the intoxicating effects of ethanol by drugs acting at the benzodiazepine-GABA receptor complex

The ability of the benzodiazepine receptor partial inverse agonists Ro 15-4513, Ro 15-3505 and FG 7142, and the picrotoxin site ligands pentylenetetrazole and Ro 5-3663 to reduce ethanol-induced intoxication were investigated. Ro 15-4513 (0.3-3 mg/kg), Ro 15-3505 (3 mg/kg), pentylenetetrazole (20 and 25 mg/kg) and Ro 5-3663 (4 mg/kg) all significantly attenuated the intoxicating effects of ethanol. In contrast, FG 7142 (20 and 40 mg/kg) failed to reduce ethanol intoxication, but reversed the effect of Ro 15-4513. This pattern of results differs from that obtained using other behavioral paradigms. Since drugs which reduce the effects of GABA generally reduce the intoxicating effects of ethanol, it is suggested that the beta-carbolines may be unusual in their interaction with ethanol.     

Anxiolytic and anxiogenic drug effects on exploratory activity in an elevated plus-maze: a novel test of anxiety in the rat

The current studies further investigated the effects, in animal models of anxiety, of novel putative anxiolytic and anxiogenic compounds believed to induce their effects by actions at the GABA-benzodiazepine receptor complex. It was expected that the results would also provide further validation for a novel test of anxiety based on the ratio of open to closed arm entries in an elevated plus maze in the rat. The novel putative anxiolytics CL 218,872 (10-20 mg/kg) and tracazolate (5 mg/kg) significantly elevated the percentage of time spent on the open arms of an elevated plus-maze, consistent with their anxiolytic activity in several other animal tests. Also consistent with results from other animal tests, no anxiolytic activity was observed for the phenylquinoline PK 8165 (10-25 mg/kg), the 3,4-benzodiazepine tofisopam (25-50 mg/kg), or buspirone (0.5-20 mg/kg). The benzodiazepine receptor inverse agonists FG 7142 (1-5 mg/kg) and CGS 8216 (3-10 mg/kg) had anxiogenic activity in this test, as did the atypical benzodiazepine Ro 5-4864 (1-5 mg/kg). Interestingly, however, the benzodiazepine receptor antagonists Ro 15-1788 (10-20 mg/kg) and ZK 93426 (5-10 mg/kg) had no anxiogenic activity in this test.     

Suppression of cytotoxic T lymphocyte (CTL) activity by FG 7142, a benzodiazepine receptor 'inverse agonist'.

A dose-dependent (12.5-100 mg/kg) suppression of cytotoxic T lymphocyte (CTL) activity was observed in mice after administration of the benzodiazepine receptor 'inverse agonist' FG 7142 (N-methyl-beta-carboline-3-carboxamide). This compound produces a syndrome resembling stress or anxiety in both animals and man. Addition of FG 7142 (1-1000 nM) to either a 4-hour 51Chromium-release assay or 5-day in vitro CTL generation system did not affect CTL activity. Pretreatment with the benzodiazepine receptor antagonist Ro 15-1788 (10 mg/kg) attenuated FG 7142-induced suppression of CTL activity, but had no effect when administered alone. Time-course studies indicated that FG 7142-induced suppression of CTL activity was long-lasting. The suppression of CTL activity by FG 7142 provides further evidence that the central nervous system pathways subserved by the benzodiazepine/GABA receptor chloride channel complex may play an important role in the modulation of immune function.     

Effects of benzodiazepine receptor ligands on the performance of an operant delayed matching to position task in rats: opposite effects of FG 7142 and lorazepam

The effects of a series of benzodiazepine (BZ) receptor ligands, ranging from a full agonist through to partial inverse agonists, were examined on short term working memory in the rat. The behavioural paradigm used was a discrete trial, operant delayed matching to position task, as originally described by Dunnett (1985), with delays of 0, 5, 15 and 30 s. The benzodiazepine receptor (BZR) full agonist lorazepam (0.25, 0.375 and 0.5 mg/kg) dose and delay dependently impaired matching accuracy. Lorazepam also increased the latency to respond and decreased the number of nose pokes made into the food tray during the delays. In contrast, the BZR partial agonist ZK 95 962 (1, 3, 10 mg/kg) did not affect matching accuracy, but did increase the speed of responding. The BZR antagonist ZK 93 426 (1.25, 5, 25 mg/kg) had no effects in this paradigm. The BZR weak partial inverse agonists Ro 15-4513 (0.1, 1 and 10 mg/kg) and ZK 90 886 (1, 3 and 10 mg/kg) did not affect accuracy of performance. However, both of these drugs increased the latency to respond and decreased nose poke responses. These motoric effects were particularly strong following 10 mg/kg Ro 15-4513. This shows that the effects of drugs on the accuracy of responding and on the speed of responding can be dissociated. The BZR partial inverse agonist FG 7142 had effects on matching accuracy that were dependent upon dose. The lowest dose of FG 7142 (1 mg/kg) significantly improved accuracy, whereas the highest dose (10 mg/kg) impaired accuracy. This impairment induced by FG 7142 (10 mg/kg) was accompanied by an increase in the latency to respond and a decrease in the number of nose pokes. Taken together, these results show that the accuracy of delayed matching performance can be modulated in opposite ways by the BZR full agonist lorazepam and a low dose of the BZR partial inverse agonist, FG 7142.