Memory enhancing, anticholinesterase and antimicrobial activities of ß-phenylnitroethane and essential oil of Dennettia tripetala Baker f.

ETHNOPHARMACOLOGICAL RELEVANCE: Dennettia tripetala Baker f. belonging to the family Annonaceae is an important food and medicinal plant used in some local communities in Southwest Nigeria. AIMS OF THE STUDY: The study aims at determining the chemical composition of the essential oil of different morphological parts of D. tripetala, the memory enhancing and anticholinesterase activities as well as the antimicrobial properties. MATERIALS AND METHODS: Essential oil of the morphological parts namely the fresh fruits, dried fruits, dried seeds and fresh leaves were obtained by hydrodistillation and analysed by GC-FID and GC-MS. The oil samples were evaluated for memory enhancement using Y-maze and in vitro anticholinesterase activities. The antimicrobial properties were also evaluated by nutrient broth method. RESULTS: GC analysis identifies ß-ocimene, linalool, ß-phenylnitroethane and humulene as common constituents of the fresh fruits, dried fruits, dried seeds and fresh leaves. ß-Phenylnitroethane (BPNE) was the predominant constituent of all the parts; with the dried seed containing 87.4% BPNE, followed by the dried fruit (78.1%), fresh leaf (62.9%) and the fresh fruit content was 61.6%. The second most predominant constituent, linalool, was highest in the fresh fruit (29.9%), followed by the fresh leaf (16.0%), the dried fruit (14.9%) and the dried seed had least linalool content (8.8%). (Z)- ß-Ocimene and humulene were other common components. The seed oil and BPNE exhibited high memory enhancing activities in the Y-maze test. However, the seed oil exhibited the best inhibition against the test bacteria and it had a broad spectrum of antimicrobial activity. Bioactivities demonstrated by the various essential oils were not solely due to BPNE; rather, synergistic effects of other components are quite obvious. CONCLUSION: The most abundant component - ß-phenylnitroethane of D. tripetala was totally responsible for its memory enhancing properties but could not solely account for its antimicrobial activity.

Neuropharmacological profile and chemical analysis of fresh rhizome essential oil of Curcuma longa (turmeric) cultivated in Southwest Nigeria.

BACKGROUND: Curcuma longa (turmeric) is commonly used as spice and also used to treat fever, cough and febrile convulsions in Nigeria. This study determined the chemical composition of the essential oil of C. longa and evaluated its neuropharmacological activity in mice. METHODS: Essential oil of C. longa (EOCL) fresh rhizome was obtained by hydrodistillation and its chemical composition determined by GC-MS. Acute toxicity (LD50) profile of the essential oil was determined orally (p.o.) and intraperitoneally (i.p.); and the EOCL (50-200 mg/kg, i.p.) was evaluated for its behavioural, anxiolytic, sedative and anticonvulsant activities using appropriate models in Albino mice (Vom Strain, Jos, Nigeria). RESULTS: Analysis of the oil showed the presence of 23 compounds with turmerone (35.9%) being the major component. The LD50 values obtained for the mice were 2154 mg/kg, p.o., and 693 mg/kg, i.p. The EOCL (50-200 mg/kg, i.p.) caused significant (p < 0.01) inhibition of rearing {F(4,20) = 9} and locomotor {F(3,16) = 42} activity; decreased head dips in hole board {F (4,20) = 4}; increased the time spent in the open arms of the elevated pus maze {F (4,20) = 9}; prolonged total sleeping time {F (4,20) = 21} induced by ketamine injection, and protected mice against pentylenetetrazol-induced convulsions. CONCLUSION: The major component of the essential oil of this C. longa species was turmerone; the oil was slightly toxic orally but moderately toxic intraperitoneally in mice; exhibited significant anxiolytic, sedative and anticonvulsant activities in mice.

Caffeine/sleep-deprivation interaction in mice produces complex memory effects.

BACKGROUND: Sleep deprivation negatively impacts memory, causing deficits in memory processes. Of interest is any agent that can offset such deficits. Mice were given varying doses of caffeine for 14 days and then deprived of sleep for 6 hours by the 'gentle handling' method. Memory was assessed using the Novel Object Recognition Test and Y maze alternation. PURPOSE: The study was designed to ascertain the impact of varying doses of caffeine combined with total sleep-deprivation on spatial and non spatial memory in mice. METHODS: Adult Swiss Webster mice of both sexes were assigned to six groups viz., vehicle (distilled water), or one of five selected doses of caffeine (10, 20, 40, 80 and 120 mg/kg) for 14 days via the oral route. Open field novel object recognition test and Y maze spatial working memory tests were carried out on day 14. Results were analysed using multi-factorial ANOVA followed by Tukey HSD test and expressed as mean ± S.E.M, with p values less than 0.05 were considered statistically significant. RESULTS: Novel object recognition tests (NOR) revealed that pre-training and pre-test sleep deprivation and caffeine combination impaired non spatial and spatial memory in male and female mice. CONCLUSION: The study shows the complex interactions with memory that may arise when total sleep deprivation is superimposed on caffeine administration.

Foraging enrichment modulates open field response to monosodium glutamate in mice.

BACKGROUND: Environmental enrichment can enhance expression of species-specific behaviour. While foraging enrichment is encouraged in laboratory animals, its impact on novelty induced behaviour remain largely unknown. PURPOSE: Here, we studied behavioural response of mice to acute and subchronic oral monosodium glutamate (MSG) in an open field with /without foraging enrichment. METHODS: Adult male mice, assigned to five groups were administered vehicle (distilled water), or one of four selected doses of MSG (10, 20, 40 and 80 mg/kg) for 21 days. Open field novelty induced behaviours i.e. horizontal locomotion, rearing and grooming were assessed after the first and last doses of MSG. Results were analysed using MANOVA followed by Tukey HSD multiple comparison test and expressed as mean ± S.E.M. RESULTS: Following acute MSG administration without enrichment, locomotor activity reduced, grooming increased, while rearing activity reduced at lower doses and increased at higher doses. Subchronic administration without enrichment was associated with increased locomotor activity and reduction in grooming, rearing activity however still showed a biphasic response. Addition of enrichment with acute administration resulted in sustained reduction in locomotor and rearing activities with a biphasic grooming response. Subchronically, there was reduction in horizontal locomotion, biphasic rearing response and sustained increase in grooming activity. CONCLUSION: Behavioural response to varying doses of MSG as observed in the open field is affected by modifications such as foraging enrichment, which can reverse or dampen the central effects seen irrespective of duration of administration.

Effect of dehusked Garcinia kola seeds on the overall pharmacokinetics of quinine in healthy Nigerian volunteers.

We investigated the effect of concurrent ingestion of Garcinia kola seed on the pharmacokinetics of quinine. In a randomized crossover study, 24 healthy Nigerian volunteers were assigned into 2 groups (A and B; n = 12 per group) on the basis of G. kola dose orally ingested. Each subject received 600 mg quinine sulfate before and after ingesting 12.5 g of G. kola once daily for 7 days (group A) or 12.5 g twice daily for 6 days and once on the seventh day (group B). Blood samples were collected and analyzed for plasma quinine and its metabolite (3-hydroxyquinine) using a validated high performance liquid chromatography method. Concurrent administration of quinine with G. kola reduced quinine tmax by 48% (group A), mean Cmax by 19% and 26% in groups A and B, respectively, and slight reduction in mean AUC0- ∞ of quinine in both groups. 3-hydroxyquinine Cmax also reduced by 29% and 32%; AUC0-∞ by 13% and 9%, respectively. The point estimates of the T/R ratio of the geometric means for all Cmax obtained and only the AUC0-∞ at a higher dose of G. kola were outside the 80%-125% bioequivalence range. In conclusion, an herb-drug interaction was noted with concurrent quinine and G. kola administration.

Anxiolytic and antidepressant like effects of natural food flavour (E)-methyl isoeugenol.

(E)-methyl isoeugenol (MIE) is a natural food flavour that constitutes 93.7% of an essential oil from Pimenta pseudocaryophyllus leaf. The leaf extracts of this species are used as a calming agent. As a ubiquitous food additive, the application of MIE for treating mood disorders appears to be globally attractive. Hence, we sought to evaluate general pharmacological activities, anticonvulsant, anxiolytic and antidepressant effects and the possible mechanisms of MIE actions. Administration of MIE was carried out prior to the exposure of a male Swiss mice to general behavioural tests, barbiturate sleep, PTZ-induced convulsion, light dark box (LDB), elevated plus maze (EPM), wire hanging, open field (OF) and forced swimming test (FST). The involvement of monoamine system was studied by mice pretreatment with WAY100635 (antagonist of 5-HT1A), α-methyl-p-tyrosine (AMPT; depletor of catecholamine) or p-chlorophenylalanine (PCPA; depletor of serotonin storage). There was no record of neurotoxic effect or animal's death during the course of general pharmacological tests. MIE at 250 and 500 mg kg(-1) potentiated the hypnotic effect of sodium pentobarbital. However, MIE did not protect against PTZ-induced convulsion. Except for MIE at 500 mg kg(-1), parameters evaluated in the LDB, EPM and OF demonstrated an anxiolytic like property of MIE. This effect was blocked by WAY100635 pretreatment. MIE at 500 mg kg(-1) elicited a reduction in locomotor activity of the mice in the OF. Anti-immobility effect of MIE 250 mg kg(-1) in the FST suggested an antidepressive like property. Unlike AMPT, pretreatment with PCPA reversed the antidepressant like effect of MIE. Our findings demonstrated anxiolytic and antidepressant like properties of (E)-methyl isoeugenol and suggested the participation of serotonergic pathways.

Hypotensive and vasorelaxant effects of (E) - methyl isoeugenol: a naturally occurring food flavour.

Application of naturally occurring (E) - methyl isoeugenol (MIE) as food flavour has been widely accepted despite the growing concerns over cardiovascular issue. Hence, we sought to investigate hypotensive property of MIE and the involvement of central and/or peripheral mechanism (s). Variation in mean arterial pressure (MAP), heart rate (HR), systolic blood pressure (SBP), baroreflex sensitivity of normotensive rats and vascular reactivity were recorded. MIE (1.11, 2.25 or 4.50mg/kg, iv) elicited dose-related decrease in MAP (-16.9±1.13; -19.0±4.18 or -27.2±3.65mmHg, respectively) and an increase in HR (17.4±1.79; 24.4±5.11 or 29.9±6.62 bmp, respectively). MIE 25 or 50mg/kg (p.o) reduced the SBP (-13.6±4.18 or -16.6±5.60mmHg, respectively) without altering baroreflex sensitivity. The hypotensive effect of MIE remained unaltered by WAY100635 (antagonist of 5-HT1A) and L-NAME (NO synthase inhibitor). Intracerebroventricular injection of MIE did not change MAP. MIE elicited endothelium independent vasorelaxation (endothelium-intact vessels, Emax 92.5±1.75%; Endothelium-denuded vessels, Emax 91.4±2.79%). MIE blocked CaCl2 or BAY K8644 (L-type voltage gated calcium channel activator)-induced vascular contractions. Our findings showed evidence of hypotensive and vasorelaxation effects of MIE with involvement of calcium channel.

Analgesic, learning and memory and anxiolytic effects of insulin in mice.

Insulin is a polypeptide hormone that is present in mammals and its main function is the maintenance of adequate blood sugar level. Insulin receptors are widely but unevenly distributed in the brain. Insulin has been reported to be involved in the regulation of neurotransmitters release. It has also been linked to the pathogenesis of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Although there is abundant literature on the study of biochemical and molecular properties of insulin, there has been no literature on its central behavioural effects on anxiety and pain relief among other behavioural effects. This study therefore investigates whether insulin has any anxiolytic and other CNS effects. This experiment was carried out in mice using animal behavioural models including a hot plate analgesic test, holeboard and elevated plus maze for anxiolytic test. A Y-maze was used for the locomotor activity and spontaneous alternation investigations. Mice were administered intraperitoneally with insulin at different doses of 0.5, 1.0 and 2.0IU/kg. The results obtained showed that insulin has no analgesic activity, however, it caused significant central inhibitory effects by decreasing both locomotor activity in both holeboard and Y-maze models and also decreased the exploratory behaviour in holeboard at doses administered dose-dependently indicating its sedative effects. In elevated plus maze, insulin had no effects on percentage of open arm entries at all doses but had a significant effect on percentage of open arm duration at the dose of 1.0IU/kg only. Insulin administration at lower doses (0.5 and 1.0IU/kg, i.p.) had no effect on spatial working memory, however, it had significant spatial working memory impairment at the dose of 2.0IU/kg, i.p. in mice. The study showed that insulin has several neuropharmacological effects at doses used.

Neuropharmacological effects of oleamide in male and female mice.

Oleamide, a fatty acid amide accumulates selectively in the cerebrospinal fluid of sleep deprived cats and rats. Oleamide has been reported to have effects on a wide range of receptors and neurotransmitter systems especially the centrally acting ones for example, dopamine acetylcholine, serotonin, gamma aminobutyric acid (GABA), cannabinoid and vanilloid among others. This suggests a wide range of central nervous system effects of the compound. The effects of intraperitoneal administered oleamide on Novelty-induced behaviours, learning and memory and forced swimming-induced depression were studied. The relative effects of the compound on the male and female mice were also noted. Oleamide dose-dependently reduced (p<0.05) novelty induced rearing, grooming and locomotion. The effects on the all NIBs started within the first 10 min of the test and the peak of the effects was observed during the third 10 min period of the test. Effect of oleamide on short-term working memory was significantly (p<0.05) affected only with the dose of 5mg/kg while the other dose of 10mg/kg had no effect. In the forced swimming test, acute triple intraperitoneal administration of oleamide at 10mg/kg induced a significant reduction in the immobility duration in mice signifying an antidepressant effect. Sex differences in the effects of oleamide (10mg/kg, i.p.) were clearly evident in active behaviours in FST. These results confirm the multiplicity of central nervous system receptors and neurotransmitters that oleamide interacts with hence its numerous and diverse neuropharmacological effects. Most importantly, the present study suggests that oleamide has antidepressant-like property.

Sedative, antiepileptic and antipsychotic effects of Spondias mombin L. (Anacardiaceae) in mice and rats.

In this study, we evaluated the effects of air-dried Spondias mombin leaves extracted with aqueous, methanol and ethanol solvents on hexobarbital-induced sleeping time and novelty-induced rearing (NIR) behaviours in mice and rats. We also studied the effect of the extracts on amphetamine- and apomorphine-induced stereotyped and picrotoxin-induced convulsive behaviour in rats. All residues from different extractions were dissolved in normal saline and administered intraperitoneally (i.p.). The methanolic and ethanolic extracts (12.5-100mg/kg i.p.) prolonged the hexobarbital-induced sleeping time and reduced the NIR in both mice and rat in a dose-dependent manner. The aqueous extract prolonged the hexobarbital-induced sleeping time and reduced (NIR) at doses of 50 and 100mg/kg. The inhibitory effect of the extracts on NIR was not reversed by atropine, yohimbine, naltrexone and flumazenil. However, the extracts blocked the facilitating effect of flumazenil. This suggests that NIR inhibitory effects of extracts of Spondia mombin are not mediated via muscarinic, alpha(2) adrenergic, and mu-opioid receptors, whereas, the extracts appear to facilitate GABAergic transmission. In addition the extracts blocked picrotoxin-induced convulsions. Phenolic compound(s) were present in the ethanolic and methanolic extracts, which exhibited anticonvulsant properties in the picrotoxin-induced convulsions model. The extracts decreased the amphetamine/apomorphine-induced stereotyped behaviour, which suggest that these extracts possess antidopaminergic activity. The effect of the extracts on hexobarbitone-induced sleeping time was blocked by flumazenil a GABA(A) antagonist, indicating that the extracts contain GABA(A) agonists. These results suggest that the leaves extracts of Spondias mombin possess sedative and antidopaminergic effects.

Neuropeptide-Y Y2-receptor agonist, PYY3-36 promotes non-rapid eye movement sleep in rat.

PYY3-36 is a major component of the gut-brain axis and peripheral administration has been reported to exert significant effects on feeding, brain function and is more selective for neuropeptide Y2 receptor. Therefore, we investigated the effects of nocturnal intraperitoneal administration of single doses of PYY3-36 (30 and 100 microg/kg i.p.) on food intake, water intake and the sleep-wake cycle in rats. Sleep recordings were carried out in male Sprague-Dawley rats implanted with cortical electroencephalogram (EEG) and neck electromyogram (EMG) electrodes. The EEG, EMG, food intake and water intake were assessed. The electrographic recordings obtained were scored visually as rapid eye movement (REM) sleep, non-REM (NREM) sleep and wakefulness. PYY3-36 administration 15 min prior to dark onset significantly (p<0.05) increased non-rapid eye movement (NREM) sleep and decreased wakefulness. Analysis of the dark-period at 4-h time intervals showed that nocturnal administration of PYY3-36 (30 and 100 microg/kg) significantly suppressed wakefulness and increased non-REM sleep during the first 4-h time interval. Time spent in wakefulness was significantly decreased after administration of PYY3-36 (30 and 100 microg/kg) when compared with administration of vehicle. In addition, PYY3-36 (30 and 100 microg/kg i.p.) induced an increase in the time spent in NREM sleep. The nocturnal intraperitoneal administration of the lower dose of PYY3-36 (30 microg/kg) also significantly decreased food intake [F (2,23)=4.90, p<0.05] but had no effect on water intake. These findings suggest that PYY3-36 may play an important role in the enhancement of NREM sleep and feeding behavior.

Selective stimulation of orexin receptor type 2 promotes wakefulness in freely behaving rats.

Orexins A and B are a pair of neuropeptides implicated in the regulation of feeding and arousal behavior mediated through two orexin receptors type 1 and type 2. We have determined the arousal effects of newly developed selective orexin receptor type 2 agonist, [Ala11]orexin-B, on the sleep-wake cycle in rats. The effects of third ventricle intracerebroventricular (ICV) infusion of the novel orexin receptor type 2 selective agonist, [Ala11]orexin-B, on the sleep-wake cycle were investigated. ICV infusion of [Ala11]orexin-B (1, 10 and 40 nmol) during the light period (11:00-16:00) dose-dependently resulted in a significant increase in wake duration by 46.9% (n = 5, P < 0.05), 159.2% (n = 4, P < 0.01) and 163.6% (n = 7, P < 0.01)), respectively, and a significant decrease in rapid eye movement (REM) (P < 0.01) and non-REM sleep (P < 0.01) for all doses. In contrast, ICV infusion of orexin B at the same doses (1, 10 and 40 nmol) caused a 16.6% (n = 6, non-significant), 99.8% (n = 6, P < 0.05) and 72.0% (n = 4, P < 0.05) increase in wakefulness, respectively. Moreover, orexin-A, which exerts its effects through orexin receptor type 1 and orexin receptor type 2 with similar potency, resulted in a significant increase in wakefulness duration by 17.1% (n = 6, P < 0.05), 184.0% (n = 6, P < 0.01) and 228.6% (n = 6, P < 0.01) at doses of 0.1, 1 and 10 nmol, respectively. Further, the enhancement of wakefulness was accompanied by a marked reduction in REM and non-REM sleep. These findings suggest that orexin receptor type 2 plays an important role in the modulation of sleep-wake state and behavioral responses.

A novel melatonin derivative modulates sleep-wake cycle in rats.

The aim of this study was to evaluate, in comparison with melatonin (MLT), the effects of a novel 2-melatonin derivative, having a 2-trifluoromethyl group (MLTD) on the sleep-wake cycle in freely behaving rats. Doses of MLTD (100, 300 and 500 nmol/100 microl saline) or MLT (500 nmol/100 microl saline) replaced the i.c.v. infusion of saline during the diurnal infusion period (7:00-17:00). Diurnal infusion of MLTD significantly (P < 0.05) increased NREM sleep at doses of 300 and 500 nmol during the second 4-h time interval of the light period and the lowest dose showed delayed effects on NREM sleep in the third 4-h time interval. However, REM sleep was only increased significantly at the dose of 500 nmol. The infusion of MLT did not have effects on REM sleep but significantly increased NREM sleep. These findings support the notion that MLTD diurnal infusion into the third ventricle produces soporific effects dose-dependently and more potently than MLT. Thus, MLTD may play an important role in studies of sleep.

Hypnotic effects of total aqueous extracts of Vervain hastata (Verbenaceae) in rats.

The in vivo sedative property of the total aqueous extract of the aerial portion of Vervain hastata (Verbenaceae) (TAEV) was studied in male rats to establish its scientific basis in herbal medicine. The investigation was conducted using electroencephalogram (EEG) analysis, and the barbituric-hypnosis test. The results showed that TAEV potentiated the pentobarbital-induced hypnosis significantly by reducing sleep latency and increased sleeping time in a dose-dependent manner that was reversed by flumazenil. The EEG data demonstrated that extract administration augmented total sleep time, rapid eye movement (REM) sleep and non-REM sleep at the expense of wakefulness. The study's results clearly showed the scientific validity for the use of this plant as a sedative and possibly as a nerve tonic substance.