Interference of antimycotics and other drugs with methohexital hypnosis in rats

Compounds of various pharmacological and chemical classes were studied for their interaction with methohexital hypnosis. Rats were treated daily for 5 days with an oral dose of a test compound or solvent. On days 1, 5, and 8 methohexital was injected intraperitoneally and the duration of hypnosis was measured. Three types of interaction with methohexital hypnosis were observed. Acute prolongation of hypnosis on day 1 was the most marked effect of fluconazole (median effective dose, ED₅₀: 8.66 mg/kg), but this occurred also with phenobarbital (ED₅₀: 26.4 mg/kg) and diphenylhydantion (ED₅₀: ～ 160 mg/kg). Tolerance to prolongation, i.e., a decrease of the hypnosis time by more than 50% from day 1 to day 5, was most marked with phenobarbital (ED₅₀: 12.6 mg/kg) and diphenylhydantion (ED₅₀: 113 mg/kg) but was also found with fluconazole (ED₅₀: 22.6 mg/kg). Shortened hypnosis times on day 8 occurred with phenobarbital (ED₅₀: ～ 40.0 mg/kg) and diphenylhydantoin (ED₅₀: ～ 160 mg/kg). The antimycotic itraconazole, the antidiarrheal loperamide, the thymosthenic agent ritanserin, and the antiallergics astemizole and levocabastine were devoid of interactions with methohexital. When compared with the basic activity of the tested compounds in rats, interference with methohexital hypnosis was most pronounced with phenobarbital (ratio 3.13) followed by fluconazole (ratio: 3.28) and diphenylhydantoin (ratio: 5.07).     

Synthesis and potential anticonvulsant activity of new aryl sulfonyl semicarbazide derivatives

In the present study on the development of new anticonvulsants, twelve new aryl sulfonyl semicarbazide derivatives were synthesized and tested for anticonvulsant activity using maximal electroshock (MES), subcutaneous pentylenetetrazole screens. Their neurotoxicity was determined by the rotorod test. The most active compound 5i showed the MES-induced seizures with ED₅₀ value of 7.3 mg/kg and TD₅₀ value of 402.3 mg/kg after intraperitoneally injection to mice, which provided compound 5i with a protective index (TD₅₀/ED₅₀) of 55.1 in the MES test.     

Increased sensitivity to rate-altering and discriminative stimulus effects of morphine following continuous exposure to naltrexone

Two experiments evaluated whether termination of a continuous infusion of naltrexone altered sensitivity to the rate-suppressing or discriminative stimulus effects of morphine in rats. An 8-day infusion of saline or doses of 3, 10, or 18 mg/kg/day naltrexone did not alter rates of lever pressing maintained under fixed-ratio 30 schedules of food delivery. A dose of 10 mg/kg/day naltrexone produced insurmountable antagonism of the rate-suppressing and analgesic effects of morphine. The ED₅₀ of morphine for rate suppression decreased by 2-fold 1 day after termination of the 8-day infusion of 10 or 18 mg/kg/day naltrexone. The ED₅₀ of morphine returned to initial values within 8 days. Termination of infusion of either saline or 3 mg/kg/day naltrexone did not alter the ED₅₀ of morphine. Changes in morphine stimulus control were evaluated in rats trained to discriminate saline and 3.2 mg/kg morphine under fixed-ratio 15 schedules of food delivery. The ED₅₀ of morphine for stimulus control or rate suppression decreased by 2-fold 1 day after termination of an 8-day infusion of 18 mg/kg/day naltrexone. The ED₅₀ of morphine for rate suppression returned to initial values within 3 days; that for stimulus control, within 5 days. Thus, termination of exposure to high doses of naltrexone produced brief changes in sensitivity to the rate-altering and discriminative stimulus effects of morphine that parallel reported changes in sensitivity to the analgesic and lethal effects of morphine.     

Structure-based design,synthesis, and anticonvulsant activity of isatin-1-N-phenylacetamide derivatives

In an effort to develop the potent anticonvulsant agents, a series of novel isatin-1-N-phenylacetamide derivatives was synthesized and screened for their in vivo anticonvulsant activity against maximal electroshock test and evaluated for their neurotoxicity by the rotarod test at the same dose levels. Ten compounds exhibited the anticonvulsant activity. 2-(5-Methyl-2,3-dioxoindolin-1-yl)-N-phenylacetamide (4b) was found to be the most potent compound of the series with an ED₅₀ of 91.3 mg/kg, TD₅₀ of >1,000 mg/kg, a higher protective index (PI = TD₅₀/ED₅₀, >11) was gained than the reference drug phenobarbital and carbamazepine. The essential structural features responsible for interaction with receptor site are established within a suggested pharmacophore.     

Comparison of acute and repeated treatment with the 5-HT1A receptor ligands 8-OH-DPAT and ipsapirone in animal models of anxiety and depression

The present study compared the 5-HT_1A receptor ligands 8-OH-DPAT and ipsapirone with diazpepam and imipramine in the shock induced ultrasonic vocalization anxiety test and the forced swimming depression test in the rat. Acutely, 8-OH-DPAT induced anxiolytic and antidepressive effects (ED₅₀: 0.12 and 1.4 mg/kg, i.p., respectively), whereas ipsapirone induced anxiolytic (ED₅₀: 0.6 mg/kg) and moderate antidepressive effects (33% at 3-10 mg/kg). Virtually no tolerance developed for the anxiolytic effects after 2 weeks of treatment with 0.03-1 mg/kg 8-OH-DPAT or 0.1-10 mg/kg ipsapirone (i.p., b.i.d.), with 10 mg/kg/day ipsapirone (s.c., mini-pumps), or with 1.5 μg/rat/hr 8-OH-DPAT (local infusion in the dorsal raphe nucleus, mini-pumps). However, some tolerance developed for the antidepressive effects of 8-OH-DPAT (ED₅₀: 0.6, 1.4, 2.5 and >3 mg/kg, after 2 weeks of pretreatment with vehicle, 0.3, 1, and 3 mg/kg 8-OH-DPAT, respectively, i.p., b.i.d.). In the case of ipsapirone, the dose-effect curve in the forced swimming test was shifted to the left after 2 weeks of pretreatment with ipsapirone (0.3-10 mg/kg, i.p., b.i.d.). Acutely, diazepam induced an anxiolytic effect (ED₅₀: 3.6 mg/kg, i.p.), but failed to induce an antidepressive effect; whereas imipramine induced an antidepressive effect (ED₅₀: 20.5 mg/kg) and a moderate anxiolytic effect (max. efficacy: 47% at 30 mg/kg). Upon repeated administration (2 weeks), diazepam (5 mg/kg) showed t0olerance for its anxiolytic effects and weak antidepressive effects emerged, whereas imipramine (20 mg/kg) showed weak sensitization for both effects. It is concluded that (a) with all compounds, tolerance, as well as sensitization can be observed, depending on the behavioral test, the dose and the type of compound; and (b) compared with the other compounds tested, relatively low doses of 5-HT_1A drugs offer the most attractive profile of mixed anxiolytic/antidepressive activity. © 1993 wiley-Liss, Inc.     

Effect of chlormethiazole,dizocilpine and pentobarbital on harmaline-induced increase of cerebellar cyclic GMP and tremor

Administration to mice of harmaline (100 mg/kg SC) resulted in a greater than two-fold increase in cyclic GMP in the cerebellum 15 min later. This response was inhibited by pretreatment 5 min before the harmaline with pentobarbital (ED₅₀ 6.5 mg/kg), chlormethiazole (ED₅₀ 10.4 mg/kg) and dizocilpine (ED₅₀ 0.5 mg/kg). Harmaline-induced tremor was inhibited by pentobarbital (ED₅₀ 30 mg/kg) and chlormethiazole (ED₅₀ 50 mg/kg) but not dizocilpine. The data demonstrate that the harmaline-induced tremor and cerebellar cyclic GMP rise are probably not associated. They also demonstrate that chlormethiazole is able to inhibit a biochemical response (the increase in cerebellar cyclic GMP) which results from increased glutamate function.     

Tricyclic Antidepressant Agents. II. Effect of Oral Administration on the Uptake of 3H-Noradrenaline and 14C-5-Hydroxytryptamine in Slices of the Midbrain-Hypothalamus Region of the Rat

Abstract: The inhibition of the simultaneous uptake of ³H-l-noradrenaline (NA) and ¹⁴C-5-hydroxytryptamine (5-HT) in slices of the midbrain-hypothalamus region of the rat brain after oral administration of desipramine, imipramine, nortriptyline, amitriptyline, chlordesipramine and chlorimipramine was determined. All compounds were more active in inhibiting the NA uptake than the 5-HT uptake. This difference was very marked for desipramine, imipramine, nortriptyline and chlordesipramine. Chlorimipramine was almost as active on the 5-HT uptake (ED₅₀ = 35 mg/kg orally) as on the NA uptake (ED₆₀ = 20 mg/kg orally) and amitriptyline had low activity on both uptake mechanisms (ED₅₀ > 50 mg/kg orally). Desipramine and imipramine were the most active compounds on the NA uptake (ED₅₀ = 8 mg/kg orally for both compounds) and the duration of the action was very long. The ED₅₀ values for nortriptyline and chlordesipramine in inhibiting the NA uptake were about 20 mg/kg orally for both compounds. The inhibition of the 5-HT uptake was less than 50% at 50 mg/kg orally for all compounds except for imipramine (ED₅₀ = 50 mg/kg orally) and for chlorimipramine. The role of the biotransformation for the inhibitory activities of imipramine, chlorimipramine and amitriptyline was investigated in animals pre-treated with SKF 525 A. The inhibitory potency of imipramine was increased by the same factor for both uptake mechanisms probably due to the large increase in the concentration of imipramine in the rat brain, which was demonstrated after the administration of ¹⁴C-imipramine. The inhibitory activity of chlorimipramine was somewhat more increased for the 5-HT uptake than for the NA uptake. The low activity of amitriptyline seems to be mainly due to poor resorption, since pretreatment of the animals with SKF 525 A only slightly increased the potency whereas intraperitoneal injection of amitriptyline had a rather marked effect on the NA uptake (ED₅₀ = 11 mg/kg intraperitoneally).     

Attenuation of 5-HT1A and 5-HT2 but not 5-HT1C receptor mediated behaviour in rats following chronic treatment with 5-HT receptor agonists,antagonists or antidepressants

The effects of chronic (10 days) treatment with serotonin (5-HT) receptor agonists on 5-HT_1A receptor mediated lower lip retraction (LLR), 5-HT_1C receptor mediated penile erections (PE) or 5-HT₂ receptor mediated head shakes (HS) were studied in rats. It was found that the 5-HT_1A and 5-HT₂ receptor mediated behaviour could be attenuated after chronic treatment, whereas 5-HT_1C receptor mediated behaviour remained unchanged. The ED₅₀ for the 5-HT_1A receptor mediated, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT)-induced LLR showed an increase from 0.07 mg/kg in placebo pretreated rats to 0.13 in 8-OH-DPAT (1mg/kg/day) pretreated rats. The number of 5-HT₂ receptor mediated (±)-1-2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.46 and 1 mg/kg)-induced HS was significantly reduced (67% and 50%, respectively) after 10 days' pretreatment with DOI (1 mg/kg/day). In the same animals the number of 5-HT_1C receptor mediated PE was increased. Ten days' pretreatment with MK 212 (0.46 mg/kg/day) failed to affect MK 212 (0.22 and 0.46 mg/kg)-induced PE. In addition, the effects of chronic treatment with some antidepressants were studied. The monoamine oxidase (MAO) inhibitor tranylcypromine (4 mg/kg/day) given for 10 days caused an increase in the ED₅₀ for 8-OH-DPAT induced LLR (ED₅₀ values were 0.06 and 0.14 mg/kg, respectively, in placebo — and tranylcypromine — pretreated rats) and attenuated MK 212 (0.22 and 0.46 mg/kg)-induced PE. Chronic treatment with mianserin (10 mg/kg/day), a tetracyclic antidepressant with 5-HT_1C and 5-HT₂ receptor antagonistic properties, did not change PE induced by MK 212, but caused an increase of PE induced by DOI and a decrease of DOI-induced HS. Ten days' pretreatment with the 5-HT re-uptake inhibitor Org 6997 (5 mg/kg/day) had no effect on MK 212-induced PE. The results demonstrate that 5-HT_1A and 5-HT₂ but not 5-HT_1C receptor mediated behaviour can be attenuated by chronic treatment with agonists for these receptors. The 5-HT_1C receptor mediated behaviour remains unchanged in response to chronic agonist treatment. Chronic treatment with antidepressants have differential effect on these behaviours. The possible implication for the mechanism of action of antidepressants is discussed.     

Antinociceptive and anti-hyperalgesic effects of bis(4-methylbenzoyl) diselenide in mice: Evidence for the mechanism of action

Abstract

Context: The organoselenium compounds have been described to demonstrate several biological activities, including pain management.

Objective: This study investigated the antinociceptive, hyperalgesic, and toxic effects of oral administration of bis(4-methylbenzoyl) diselenide (BMD) in mice.

Materials and methods: The antinociceptive and anti-hyperalgesic effects of BMD (1, 5, 10, 25, and 50?mg/kg, p.o.) were evaluated using models of nociception: formalin, capsaicin, bradykinin (BK), cinnamaldehyde, phorbol myristate acetate (PMA), 8-bromo-cAM, and glutamate-induced nociception; and mechanical hyperalgesia induced by carrageenan (Cg) or complete Freund's adjuvant (CFA). The acute toxicity was evaluated by biochemical markers for hepatic and renal damages.

Results: BMD significantly inhibited the licking time of the injected paw in the early and late phases of a formalin test with ED₅₀ values of 14.2 and 10.8?mg/kg, respectively. This compound reduced nociception produced by capsaicin (ED₅₀ of 32.5?mg/kg), BK (ED₅₀ of 24.6?mg/kg), glutamate (ED₅₀ of 28.7?mg/kg), cinnamaldehyde (ED₅₀ of 18.9?mg/kg), PMA (ED₅₀ of 9.6?mg/kg), and 8-bromo-cAMP (ED₅₀ of 24.8?mg/kg). In the glutamate test, the pretreatment with nitric oxide (NO) precursor, l-arginine, reversed antinociception caused by BMD or N^ω-nitro-l-arginine (_L-NOARG), but the effect of BMD was not abolished by naloxone. Mechanical hyperalgesia induced by Cg and CFA was attenuated by BMD, 70?±?4% and 65?±?4%, respectively. Furthermore, a single oral dose of BMD did not change plasma aspartate (AST) and alanine aminotransferase (ALT) activities or urea and creatinine levels.

Conclusion: BMD demonstrated as a promising compound because of the antinociceptive and anti-hyperalgesic properties in mice.     

Relative efficacies of benzodiazepine receptor agonists in affecting red nucleus electrical activity in rabbits

The effects of benzodiazepine receptor agonists on the electrical activity of red nucleus (RN) and neocortex were studied in rabbits. Under basal conditions, 30–40 µV, 40–50 Hz waves were recorded in RN. An increase of the amplitude (E_max, 75–90 µV) was found after IV injection of flunitrazepam (ED₅₀, 0.14 mg/kg), diazepam (ED₅₀, 0.28 mg/kg), alpidem (ED₅₀, 1.57 mg/kg) and zolpidem (ED₅₀, 0.73 mg/kg). Clonazepam (ED₅₀, 0.12 mg/kg) and C1 218,872 (ED₅₀, 0.63 mg/kg) were less effective. In contrast, 2–10-fold higher doses were required to induce a slight decrease of the frequency. At the level of the cortex all benzodiazepine agonists induced synchronization and spindles. The effects of diazepam (5 mg/kg IV) in both areas were antagonized by flumazenil (0.04 mg/kg IV) and bicuculline (0.2 mg/kg IV). Pentamethylentetrazole (10–30 mg/kg IV) selectively abated the effect at the level of the cortex, whereas both clonazepam (2 mg/kg IV) and -CCM (0.6 mg/kg IV) selectively suppressed only the effects on the RN. These results suggest that activation of benzodiazepine receptor mainly influences the RN waves amplitude. The efficacy in increasing the amplitude appears related to the reported relative efficacy of the compound in potentiating GABA responses. The possibility exists that these effects are dependent upon the partial or full agonist action of the drugs or upon their binding at distinct benzodiazepine receptor types.     

Tolerance and cross-tolerance to morphine-like stimulus effects of µ opioids in rats

 The purpose of these experiments was to examine the relationship of agonist relative efficacy to the pattern of tolerance and cross-tolerance to the morphine-like stimulus effects of three opioid agonists. Rats were trained to discriminate 3.2 mg/kg morphine from saline under fixed-ratio 15 schedule of food reinforcement. Morphine, nalbuphine, and fentanyl produced dose-dependent increases in morphine-like stimulus effects and decreases in response rates. Repeated treatment with 20 mg/kg per day morphine increased the ED₅₀ for stimulus control by fentanyl, morphine, or nalbuphine two-, four-, or 40-fold, respectively. Repeated treatment with 64 mg/kg per day nalbuphine increased the ED₅₀ for stimulus control for morphine by two-fold, but lower or higher treatment doses had no significant effect. Treatment with 100 mg/kg per day nalbuphine increased the ED₅₀ for nalbuphine by six-fold. Repeated treatment with 0.22 mg/kg per day fentanyl increased the ED₅₀ for stimulus control by fentanyl or morphine by approximately two-fold. Comparisons among treatment conditions suggested that magnitude of tolerance to morphine-like stimulus effects did not vary as an inverse function of the relative efficacy of the agonist used for repeated treatment. Rather repeated morphine and fentanyl treatments produced comparable tolerance, whereas repeated nalbuphine treatment did not evoke substantial tolerance. Comparisons within treatment conditions, however, suggested that magnitude of tolerance may vary inversely with relative efficacy of the agonist tested for morphine-like stimulus effects. During treatment with morphine or fentanyl, greater tolerance was observed to the morphine-like stimulus effects of the lower efficacy agonist relative to the higher efficacy agonist. Received: 17 September 1996 / Final version: 13 March 1997     

Inhibition of IL-1 release from human monocytes and suppression of streptococcal cell wall and adjuvant-induced arthritis in rats by an extract of Tripterygium wilfordii Hook

1. It was investigated whether an extract of Tripterygium wilfordii Hook f (TW) inhibits IL-1 production by monocytes and suppresses the development of IL-1-dependent arthritis induced in rats with streptococcal cell wall and adjuvant.2. TW preferentially inhibited IL-1α and IL-1β production by bacterial lipopolysaccharide (LPS)-stimulated human monocytes with IC₅₀ of approximately 1 μg/ml.3. Oral administration of TW dose-dependently suppressed joint swelling and structural damage in streptococcal cell wall-induced arthritis (ED₅₀ = 20 mg/kg/day) and in adjuvant-induced arthritis (ED₅₀ = 46 mg/kg/day for developing and 8/mg/kg/day for established arthritis).     

Lasting neurobehavioral abnormalities in rats after neonatal activation of serotonin 1A and 1B receptors: possible mechanisms for serotonin dysfunction in autistic spectrum disorders

Rationale

Perinatal exposure of rats to selective serotonin reuptake inhibitors (SSRIs) produces sensory and social abnormalities paralleling those seen in autistic spectrum disorders (ASDs). However, the possible mechanism(s) by which this exposure produces behavioral abnormalities is unclear.

Objective

We hypothesized that the lasting effects of neonatal SSRI exposure are a consequence of abnormal stimulation of 5-HT_1A and/or 5-HT_1B receptors during brain development. We examined whether such stimulation would result in lasting sensory and social deficits in rats in a manner similar to SSRIs using both direct agonist stimulation of receptors as well as selective antagonism of these receptors during SSRI exposure.

Methods

Male and female rat pups were treated from postnatal days 8 to 21. In Experiment 1, pups received citalopram (20 mg/kg/day), saline, (±)-8-hydroxy-dipropylaminotetralin hydrobromide (8-OH-DPAT; 0.5 mg/kg/day) or 7-trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2-a]-quinoxaline dimaleate (CGS-12066B; 10 mg/kg/day). In Experiment 2, a separate cohort of pups received citalopram (20 mg/kg/day), or saline which was combined with either N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclo-hexanecarboxamide maleate (WAY-100635; 0.6 mg/kg/day) or N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)-1-1′-biphenyl-4-carboxamide (GR-127935; 6 mg/kg/day) or vehicle. Rats were then tested in paradigms designed to assess sensory and social response behaviors at different time points during development.

Results

Direct and indirect neonatal stimulation of 5-HT_1A or 5-HT_1B receptors disrupts sensory processing, produces neophobia, increases stereotypic activity, and impairs social interactions in manner analogous to that observed in ASD.

Conclusion

Increased stimulation of 5-HT_1A and 5-HT_1B receptors plays a significant role in the production of lasting social and sensory deficits in adult animals exposed as neonates to SSRIs.     

6-[(N-2,3-dichlorophenyl)amino]-7-chloro-5,8-quinolinedione treatment of candidiasis in normal mice

6-[(N-2,3-Dichlorophenyl)amino]-7-chloro-5,8-quinolinedione (RCK11) was tested forin vivo antifungal activities in the treatment of systemic infection withCandida albicans in normal mice compared with ketoconazole. The therapeutic potential of RCK11 had been assessed by evaluating their activities (survival rates) against systemic infections in normal mice. ED₅₀ of intraperitoneally administered RCK11 was 0.10±0.01 mg/kg but that of ketoconazole had 8. 00±0.73 mg/kg respectively. When RCK11 was administered intravenously at the ED₅₀ (0.10 mg/kg), the colony counts ofCandida albicans in the liver after 7 days and 14 days were reduced as likely as ketoconazole at the ED₅₀ (8.00 mg/kg), and the better survival rates than ketoconazole were achieved after 14 days. The results suggest that RCK11 may be a potent antifungal agent.     

Discriminative stimulus effects of S(−)–methcathinone (CAT): a potent stimulant drug of abuse

Methcathinone (“CAT”) is a CNS stimulant that is a very significant drug of abuse in the former Soviet Union. It has also appeared on the clandestine market in the United States and has been recently classified as a Schedule I substance. In the present study, S(−)-methcathinone [S(−)-CAT, 0.50 mg/kg, IP] was employed as the training drug in a two-lever drug discrimination task in rats. Once established, the S(−)-CAT stimulus was shown to have a rapid onset to action (within 5 min) and a duration of effect of approximately 60–90 min. In tests of stimulus generalization (substitution), the S(−)-CAT (ED₅₀ = 0.11 mg/kg) stimulus generalized to S(+)-methamphetamine (ED₅₀ = 0.17 mg/kg), S(−)-cathinone (ED₅₀ =  0.19 mg/kg), S(+)-amphetamine (ED₅₀ = 0.23 mg/kg), aminorex (ED₅₀ = 0.27 mg/kg), (±)-CAT (ED₅₀ = 0.25 mg/kg), (±)-cathinone (ED₅₀ = 0.41 mg/kg), R(+)-CAT (ED₅₀ = 0.43 mg/kg), cis-4-methylaminorex (ED₅₀ = 0.49 mg/kg), methylphenidate (ED₅₀ = 0.83 mg/kg), and cocaine (ED₅₀ = 1.47 mg/kg). S(−)-CAT-stimulus generalization did not occur to fenfluramine, a structurally related nonstimulant anorectic. Lastly, haloperidol (AD₅₀ = 0.18 mg/kg), a dopamine receptor antagonist, potently antagonized the S(−)-CAT stimulus. It is concluded that S(−)-methcathinone is a very potent CNS stimulant, which appears to produce its stimulus effect, at least in part, via a dopaminergic mechanism. Received: 4 August 1997/Final version: 27 March 1998     

Anticonvulsant potencies of the enantiomers of the neurosteroids androsterone and etiocholanolone exceed those of the natural forms

Rationale

Androsterone [(3α,5α)-3-hydroxyandrostan-17-one; 5α,3α-A] and its 5β-epimer etiocholanolone [(3α,5β)-3-hydroxyandrostan-17-one; 5β,3α-A)], the major excreted metabolites of testosterone, are neurosteroid positive modulators of GABA_A receptors. Such neurosteroids typically show enantioselectivity in which the natural form is more potent than the corresponding unnatural enantiomer. For 5α,3α-A and 5β,3α-A, the unnatural enantiomers are more potent at GABA_A receptors than the natural forms.

Objectives

The aim of this study was to compare the anticonvulsant potencies and time courses of 5α,3α-A and 5β,3α-A with their enantiomers in mouse seizure models.

Methods

Steroids were administered intraperitoneally to male NIH Swiss mice 15 min (or up to 6 h in time course experiments) prior to administration of an electrical stimulus in the 6-Hz or maximal electroshock (MES) seizure tests or the convulsant pentylenetetrazol (PTZ).

Results

In the 6-Hz test, the ED₅₀ values of ent-5α,3α-A was 5.0 mg/kg whereas the value for 5α,3α-A was 12.1 mg/kg; the corresponding values in the PTZ seizure test were 22.8 and 51.8 mg/kg. Neurosteroid GABA_A receptor-positive allosteric modulators are generally weak in the MES seizure test and this was confirmed in the present study. However, the atypical relative potency relationship was maintained with ED₅₀ values of 140 and 223 mg/kg for ent-5α,3α-A and 5α,3α-A, respectively. Similar relationships were obtained for the 5β-isomers, except that the enantioselectivity was accentuated. In the 6-Hz and PTZ tests, the ED₅₀ values of ent-5β,3α-A were 11.8 and 20.4 mg/kg whereas the values for 5β,3α-A were 57.6 and 109.1 mg/kg. Protective activity in the 6-Hz test of ent-5α,3α-A persisted for somewhat longer (~5 h) than for 5α,3α-A (~4 h); protection by ent-5β,3α-A also persisted longer (~3 h) than for 5β,3α-A (~2 h).

Conclusions

The unnatural enantiomers of 17-keto androgen class neurosteroids have greater in vivo potency and a longer duration of action than their natural counterparts. The more prolonged duration of action of the unnatural enantiomers could reflect reduced susceptibility to metabolism. Unnatural enantiomers of androgen class neurosteroids could have therapeutic utility and may provide advantages over the corresponding natural isomers due to enhanced potency and improved pharmacokinetic characteristics.     

AM2389, a high-affinity,in vivo potent CB<Subscript>1</Subscript>-receptor-selective cannabinergic ligand as evidenced by drug discrimination in rats and hypothermia testing in mice

Rationale

The endocannabinoid signaling system (ECS) has been targeted for developing novel therapeutics since ECS dysfunction has been implicated in various pathologies. Current focus is on chemical modifications of the hexahydrocannabinol (HHC) nabilone (Cesamet^®).

Objective

To characterize the novel, high-affinity cannabinoid receptor 1 (CB₁R) HHC-ligand AM2389 [9β-hydroxy-3-(1-hexyl-cyclobut-1-yl)-hexahydrocannabinol in two rodent pre-clinical assays.

Materials and methods

CB₁R mediation of AM2389-induced hypothermia in mice was evaluated with AM251, a CB₁R-selective antagonist/inverse agonist. Additionally, two groups of rats discriminated the full cannabinergic aminoalkylindole AM5983 (0.18 and 0.56 mg/kg) from vehicle 20 min post-injection in a two-choice operant conditioning task motivated by 0.1% saccharin/water. Generalization/substitution tests were conducted with AM2389, AM5983, and Δ⁹-tetrahydrocannabinol (Δ⁹-THC).

Results

Δ⁹-THC (30 mg/kg)-induced hypothermia exhibited a faster onset and shorter duration of action compared with AM2389 (0.1 and 0.3 mg/kg). AM251 (3 and 10 mg/kg) attenuated/blocked hypothermia induced by 0.3 mg/kg AM2389. In drug discrimination, the order of potency was AM2389?>?AM5983?>?Δ⁹-THC with ED₅₀ values of 0.0025, 0.0571, and 0.2635 mg/kg, respectively, in the low-dose condition. The corresponding ED₅₀ values in the high-dose condition were 0.0069, 0.1246, and 0.8438 mg/kg, respectively. Onset of the effects of AM2389 was slow with a protracted time-course; the functional, perceptual in vivo half-life was approximately 17 h.

Conclusions

This potent cannabinergic HHC exhibited a slow onset of action with a protracted time-course. The AM2389 chemotype appears well suited for further drug development, and AM2389 currently is used to probe behavioral consequences of sustained ECS activation.

     

Chlorpromazine as a discriminative stimulus in rats: Generalization to typical and atypical antipsychotics

The discriminative stimulus properties of the typical antipsychotic chlorpromazine were examined in a two‐lever drug discrimination procedure for food reward. Six of nine rats readily acquired the discrimination between 1.0 mg/kg chlorpromazine (i.p.) and vehicle in a mean of 29.7 training sessions. The chlorpromazine generalization curve was dose‐dependent and yielded an ED₅₀ of 0.305 mg/kg (95% confidence interval (CI) = 0.201–0.463 mg/kg). The chlorpromazine cue generalized to the atypical antipsychotics clozapine (ED₅₀ for the clozapine curve was 0.258 mg/kg [95% CI = 0.047–1.420 mg/kg]) and olanzapine (ED₅₀ for the olanzapine curve was 0.199 mg/kg [95% CI = 0.076–0.522 mg/kg]) and to the typical antipsychotic thioridazine (ED₅₀ for the thioridazine curve was 3.103 mg/kg [95% CI = 1.993–4.832 mg/kg]). Haloperidol (a typical antipsychotic) and raclopride (an atypical antipsychotic) did not substitute for chlorpromazine. It is clear from the present results that the discriminative stimulus properties of chlorpromazine share similarities both with the atypical antipsychotics clozapine and olanzapine and with the typical antipsychotic thioridazine. The extent to which the discriminative stimulus properties of antipsychotic drugs reflect or are predictive of their therapeutic effects in schizophrenic patients remains unclear. Drug Dev. Res. 48:38–44, 1999. © 1999 Wiley‐Liss, Inc.     

The preclinical antipsychotic evaluation of HRP 913, a novel benzisoxazole derivative

HRP 913 {1-[3-(6-fluoro-1,2-benzisoxazole-3-yl)propyl]-4-(2-oxo-1-benzimidazolinyl)} piperidine demonstrated preclinical antipsychotic activity with features that may provide a clinical advantage over current therapy. It was effective in blocking amphetamine stereotypy in rats (ED₅₀ = 0.4 mg/kg, i.p.), amphetamine circling in SN-lesioned rats (ED₅₀ = 0.3 mg/kg, i.p.), apomorphine stereotypy in rats (ED₅₀ = 0.8 mg/kg, i.p.), but not apomorphine circling in SN-lesioned rats (up to 10 mg/kg, i.p.). It also blocked Sidman avoidance in rats (ED₅₀ = 0.17 mg/kg, i.p.) and monkeys (ED₅₀ = 0.2 mg/kg, p.o.) and blocked intracranial self-stimulation in rats (0.09 mg/kg, i.p.). A unique biphasic effect on catalepsy was found. Monkey EPS studies demonstrate a potential for EPS that is lower than some existing clinical standards. HRP 913 displaced ³H-spiroperidol from rat striatal sites (IC₅₀ = 6.0 × 10^?9 M) and inhibited WB-4101 binding (IC₅₀ = 2.6 × 10^?8 M) with only slight effect on QNB binding. HRP 913 does not appear to have marked α-blocking properties in vivo. HRP 913 is a potent dopamine antagonist and is predicted to have less side effects than current therapy.     

Anti‐inflammatory and antinociceptive effects of tilifodiolide,isolated from Salvia tiliifolia Vahl (Lamiaceae)

Salvia tiliifolia Vahl (Lamiaceae) is used for the empirical treatment of pain and inflammation. The diterpenoid tilifodiolide (TFD) was isolated from Salvia tiliifolia. The in vitro anti‐inflammatory effects of TFD (0.1–200 µM) were assessed using murine macrophages stimulated with LPS and estimating the levels of pro‐inflammatory mediators for 48 h. The in vivo anti‐inflammatory activity of TFD was assessed using the carrageenan‐induced paw edema test for 6 h. The antinociceptive effects of TFD were evaluated using the formalin test and the acetic acid induced‐writhing test. The effects of TFD on locomotor activity were assessed using the open field test and the rotarod test. TFD inhibited the production of TNF‐α (IC₅₀ = 5.66 µM) and IL‐6 (IC₅₀ = 1.21 µM) in macrophages. TFD (200 mg/kg) showed anti‐inflammatory effects with similar activity compared to 10 mg/kg indomethacin. The administration of TFD induced antinociception in the phase 1 (ED₅₀ = 48.2 mg/kg) and the phase 2 (ED₅₀ = 28.9 mg/kg) of the formalin test. In the acetic acid assay, TFD showed antinociceptive effects (ED₅₀ = 32.3 mg/kg) with similar potency compared to naproxen (ED₅₀ = 36.2 mg/kg). In the presence of different inhibitors in the acetic acid assay, only the co‐administration of TFD and naloxone reverted the antinociceptive activity shown by TFD alone. TFD did not affect locomotor activity in mice. TFD exerts in vitro and in vivo anti‐inflammatory activity and in vivo antinociceptive effects.