Buspirone: correlation of its anxiolytic and electroencephalographic effects

The influence of diazepam (1 and 5 mg/kg, i. p.) and buspirone (5 and 10 mg/kg) on the Fourier's spectral EEG power of sensomotor cortex and a conflict behavior in freely moving rats were studied. Diazepam (1 mg/kg) and buspirone (5 mg/kg) produced slowing of EEG theta-activity. Large doses of diazepam and buspirone produced different and multiple EEG effects. To 15-1788 (10 mg/kg) completely antagonized all the effects of diazepam (5 mg/kg). The authors discuss possible mutual relations between the influence on EEG and anxiolytic effect of these tranquilizers.     

An analysis of the differences in the effects of diazepam on the EEG of noninbred white rats with high and low expression of anxiolytic action in a conflict situation]

The effects of diazepam (5 mg/kg, i.p.) on the EEG power spectra of the sensorimotor cortex and the dorsal hippocampus were studied in albino rats with different types of conflict behaviour. "Active" rats were characterized by domination of the theta-activity in their background cortical EEG-spectra, "passive" ones--by that of the delta-activity. No differences were revealed in the background hippocampal EEG-spectra. Diazepam produced slowing of the theta-activity and increased the beta-activity in a band of 12-32 Hz in "active" rats and that in a band of 12-16 Hz in "passive" ones. The finding is usefull for studying individual animal sensitivity to drugs effects.     

Cortexolone as a modulator of diazepam activity

The influence of ACTH (200 micrograms/kg), corticosterone (20 mg/kg) and cortexolone (20 mg/kg) on the anxiolytic activity of diazepam was studied. ACTH partly and corticosterone completely blocked the action of diazepam. Cortexolone injection 30 min before the administration of diazepam induced a 100% anxiolytic effect of diazepam in the range of doses from 0.1 to 0.3 mg/kg (ED50 of anxiolytic diazepam effect is 0.2 mg/kg). The role of stress hormones in the regulation of psychotropic drug activity is discussed.     

Tolerance in the anxiolytic profile following repeated administration of diazepam but not buspirone is associated with a decrease in the responsiveness of postsynaptic 5-HT-1A receptors

To understand the role of serotonin (5-hydroxytryptamine; 5-HT)-1A receptors in the treatment of anxiety and the development of tolerance to benzodiazepines the present study was designed to monitor the responsiveness of postsynaptic 5-HT-1A receptors following repeated administration of diazepam and buspirone. Results show that tolerance in the anxiolytic profile is produced following repeated administration (2 weeks) of diazepam (2 mg/kg) but not buspirone (0.5 mg/kg). The behavioral effects of 8-OH-DPAT at a dose of 0.25 mg/kg were monitored 3 days after repeated administration of saline or buspirone or diazepam. The results show that 8-OH-DPAT elicited forepaw treading was smaller in repeated diazepam but not repeated buspirone injected rats, while hyperlocomotive effects of 8-OH-DPAT were smaller in both repeated buspirone and repeated diazepam injected rats. The results suggest that postsynaptic 5-HT-1A receptor-dependent responses were attenuated following long-term administration of diazepam but not buspirone. Role of 5-HT-1A receptors in the development of tolerance to the anxiolytic effects of diazepam but not buspirone is discussed.     

Effect of GABA-negative preparations on the anxiolytic and sedative effects of diazepam

Experiments on rats have shown that bicuculline (2 mg/kg) and picrotoxin (2 mg/kg) abolish the anxiolytic action of diazepam (2.5 mg/kg). Bicuculline (2 and 4 mg/kg) decreases while picrotoxin transforms the sedative effect of diazepam to the anxiolytic one. Picrotoxin (2 mg/kg) reduces the sedative action of gamma-acetylenic GABA (100 mg/kg) but does not favour the manifestation of its anxiolytic effect. It is suggested that the GABA-ergic mechanisms play an important role in the sedative effect of diazepam.     

Positive modulation of diazepam activity by cortexolone in alcoholic rats

It has been shown that glucocorticoid receptor antagonist-cortexolone--increased anxiolytic action of diazepam in alcoholic rats. Neither diazepam (2 mg/kg), nor cortexolone (20 mg/kg) alone influenced voluntary ethanol consumption in alcoholic rats during 14 days of administration, however, combined administration of diazepam and cortexolone diminished ethanol consumption. Receptor and permissive mechanism of gluco- and antiglucocorticoid effect on the action of diazepam are being discussed.     

Convulsant component of a depressant benzodiazepine

The convulsant influence of high doses of diazepam, in the presence of the benzodiazepine receptor antagonist Ro 15-1788, was studied in rats. Animals were implanted with permanent cortical screw electrodes for EEG recording. EEG spiking and accompanying clonic activity was observed in rats receiving greater than or equal to 200 mg/kg diazepam, followed 10 minutes later by Ro 15-1788 (20 mg/kg). Pentylenetetrazole and picrotoxin seizure thresholds, measured during constant rate iv infusion, were significantly lowered by pretreatment with diazepam (250 mg/kg) and Ro 15-1788 (20 mg/kg) administered 30 and 20 minutes, respectively, before seizure threshold measurement. It is proposed that this convulsive activity of diazepam is mediated through the picrotoxinin receptor.     

Effects of cholecystokinin tetrapeptide (CCK(4)) and of anxiolytic drugs on GABA outflow from the cerebral cortex of freely moving rats

The effect of cholecystokinin tetrapeptide (CCK(4)) and of different anxiolytic drugs on GABA outflow from the cerebral cortex was investigated in freely moving rats, by using the epidural cup technique. CCK(4) (3-30 microg/kg, i.p.) increased GABA outflow and induced objective signs of anxiety. These neurochemical and behavioral responses were prevented by the CCK(B) antagonist GV150013 at 0.1 microg/kg (i.p.). At higher doses (up to 30 microg/kg) this compound per se reduced GABA release and caused sedation, suggesting the presence of a CCKergic positive tonic modulation on GABA interneurons. Similarly the GABA(A) receptors modulator, diazepam (2mg/kg, i.p.) and the 5-HT(1A) agonist buspirone (3mg/kg, i.p.) reduced GABA outflow and caused the expected behavioral effects (reduced muscle tone, mild 5-HT syndrome) which were prevented by the respective, selective antagonists, flumazenil (1mg/kg, i.p.) and NAN-190 (3mg/kg, i.p.). These findings support the idea that GV150013, diazepam and buspirone inhibit GABAergic cortical activity, through the respective receptors. This neurochemical effect may represent the end-effect of various anxiolytic compounds affecting the cortical circuitry.     

Stress- and Yohimbine-Induced Release of Cholecystokinin in the Frontal Cortex of the Freely Moving Rat: Prevention by Diazepam but Not Ondansetron

Abstract: The in vivo release of cholecystokinin (CCK)-like material (CCKLM) was measured in the frontal cortex of freely moving rats using the microdialysis technique combined with a sensitive radioimmunoassay. Local perfusion of K⁺ (100 m M )-enriched artificial CSF resulted in a 10-fold increase in CCKLM outflow, as compared with that occurring under basal resting (K⁺ = 3.0 m M ) conditions, and this effect could be completely prevented by removal of Ca²⁺ in the perfusing fluid. Chromatographic analyses demonstrated that CCK-8S contributed to 70% of CCKLM. Stressful stimuli such as a 2-min exposure to diethyl ether and a 30-min restraint produced a marked but transient increase in cortical CCKLM release. In addition, anxiety-like behavior induced by the systemic administration of yohimbine (5 mg/kg i.p.) was associated with a long-lasting enhancement in the peptide outflow. Pretreatment with the potent anxiolytic drug diazepam (5 mg/kg i.p., 5 min before each condition), which exerted no effect on its own, completely prevented CCKLM overflow due to diethyl ether, restraint, or yohimbine administration. In contrast, neither the systemic injection (0.1 mg/kg i.p.) nor the local application (100 µ M through the microdialysis probe) of the serotonin 5-HT₃ antagonist ondansetron affected the increased release of CCKLM in rats restrained for 30 min or treated with yohimbine. These results indicate that cortical CCKergic neurotransmission is increased during stress or anxiety-like behavior in rats. Prevention of this effect by diazepam suggests that an inhibitory influence of benzodiazepines on cortical CCKergic neurons might participate in the anxiolytic action of these drugs.     

Comparison of neurokinin SP with diazepam in effects on memory and fear parameters in the elevated T-maze free exploration paradigm.

The elevated T-maze was combined with a free exploration protocol, which, in contrast to the conventional procedure, dispenses with handling of the animals during the experimental sessions. This allows measurement of fear indexes derived from the elevated plus-maze as well as assessment of acquisition of open arm avoidance and open arm escape in one continuous session. Retention of the different fear-responses is measured 72 h later without drug treatment. In order to assess the effects of two known anxiolytics in this paradigm, rats received an IP injection of diazepam (1 to 4 mg/kg), substance P (5 to 500 microg/kg) or vehicle (1 ml/kg) and were tested on the T-maze for 5 min. Diazepam elevated open arm activity, indicative of an anxiolytic effect. The drug also increased the latency to escape from the open arms, but did not significantly affect acquisition of open arm avoidance. During the retention trial, diazepam in higher doses impaired the performance of both fear-responses, suggestive of an anterograde amnesic effect. Substance P did not influence acquisition and retention of open arm avoidance and escape. However, in high doses, the peptide increased the sojourn time in the central arena of the maze, indicating reduced fear and, hence, a dissociation between anxiolytic and amnesic effects. The present findings demonstrate that the elevated T-maze free exploration paradigm is sensitive to anxiolytic and memory-modulating effects of drugs.     

Anticonflict properties of the dipeptide Litoralon and of diazepam in rats

The anticonflict properties of the anxiolytic diazepam and of the dipeptide Litoralon gamma-L-glutamyl-taurine and two of its analogues SZJ 3388, gamma-aminobutyryl-ethanolamine phosphate, and SZJ 3361, D-1-aminoisobutyrylethanolamine phosphate have been investigated in a "time-to-emerge" conflict paradigm in non-deprived rats. Diazepam, Litoralon and compound SZJ 3388 significantly decreased the "time-to-emerge" latency (TTE latency) in a dose-dependent manner versus saline- or vehicle-treated controls in doses between 0.05 and 0.50 mg/kg intraperitoneally. The analogue SZJ 3361 was inactive as regards the TTE latency, while the anti-histaminic promethazine lengthened the TTE latency in a dose-dependent manner. The number of irresolute responses was significantly decreased following administration of diazepam, SZJ 3388 and Litoralon and was positively correlated with the TEE latency-decreasing activity of these compounds. The data are discussed in terms of the benzodiazepine-like anxiolytic or anti-conflict properties of these dipeptides.     

Asparagus racemosus Attenuates Anxiety-Like Behavior in Experimental Animal Models

Asparagus racemosus Linn. (AR) is used worldwide as a medicinal plant. In the present study, the anxiolytic activity of standardized methanolic extract of root of AR (MAR) was evaluated in open-field test (OFT), hole-board, and elevated plus maze (EPM) tests. Rats received oral pretreatment of MAR in the doses of 50, 100, and 200 mg/kg daily for 7 days and then were evaluated for the anxiolytic activity in different animal models. Both MAR (100 and 200 mg/kg) and diazepam (1 mg/kg, p.o.) increased the grooming behavior, number of central squares crossed, and time spent in the central area during OFT. Further, MAR (100 and 200 mg/kg) increased the head-dip and head-dip/sniffing behavior, and decreased sniffing activity in hole-board test. Furthermore, MAR (100 and 200 mg/kg) increased the percentage entries and time spent to open arm in EPM test paradigm. The anxiolytic activity in the experimental models was similar to that of diazepam. MAR (100 and 200 mg/kg) enhanced the level of amygdalar serotonin and norepinephrine. It also increased the expression of 5-HT_2A receptors in the amygdala. In another set of experiment, flumazenil attenuated the anxiolytic effect of minimum effective dose of MAR (100 mg/kg) in OFT, hole-board, and EPM tests, indicating GABA_A-mediated mechanism. Moreover, the anxiolytic dose of MAR did not show sedative-like effect in OFT and EPM tests compared to diazepam (6 mg/kg, p.o.). Thus, the anxiolytic response of MAR may involve GABA and serotonergic mechanisms. These preclinical data show that AR can be a potential agent for treatment of anxiety disorders.     

Anxiolytic-like effect of succinic acid in mice

The putative anxiolytic activity of succinic acid was examined in male mice by using a number of experimental paradigms of anxiety and compared with that of the known anxiolytic compound diazepam. Use of the elevated plus-maze test revealed that diazepam (1.0, 2.0 and 4.0 mg/kg, PO) or succinic acid (3.0 or 6.0 mg/kg, PO) increased the percentage of entries into open arms and of time spent on open arms. In novel food consumption test, succinic acid (3.0, 6.0, and 12.0 mg/kg, IP) caused significant increases in food intake during 5 min when compared with the vehicle. In the stress-induced hyperthermia test, 40 min after drug administration rectal temperature was measured, succinic acid at dose of 1.5 mg/kg, inhibited stress-induced hyperthermia. Thus, these findings indicated that, in contrast with diazepam, succinic acid exhibits anxiolytic-like effect.     

Anxiolytic effect of berberine on exploratory activity of the mouse in two experimental anxiety models: interaction with drugs acting at 5-HT receptors

The aim of this study was to assess the anxiolytic effect of berberine (abbrev. BER) using two experimental anxiety models in the mouse. In the black and white test of anxiety, berberine (100, 500 mg/kg) produced an increase in the first time entry, time spent in the white section, and total changes between two compartments. On the other hand, in the elevated plus-maze test, berberine (100, 500 mg/kg) produced an increase in the time spent and arm entries in the open arms, and a decrease in the time spent and arm entries in the closed arms. Berberine (500 mg/kg) decreased locomotor activity in mice. Furthermore, BER at 100, 500 mg/kg decreased concentrations of NE, DA and 5-HT, and increased the concentrations of VMA, HVA and 5-HIAA in the brain stem. BER also attenuated the anxiogenic effect of WAY-100635, 8-OH DPAT and DOI and enhanced the anxiolytic effect of BUS, p-MPPI and RIT in the elevated plus-maze. These results suggested that berberine at 100 mg/kg had a significant anxiolytic-like effect, which was similar to that observed with 1 mg/kg diazepam and 2 mg/kg buspirone. The anxiolytic mechanism of BER might be related to the increase in turnover rates of monoamines in the brain stem and decreased serotonergic system activity. Moreover, BER decreased serotonergic system activity via activation of somatodendritic 5-HT1A autoreceptors and inhibition of postsynaptic 5-HT1A and 5-HT2 receptors.     

Regionally specific effects of diazepam on brain serotonin metabolism in rats: Sustained effects following repeated administration

The effects of single (1mg/kg) and repeated (1mg/kg 2¹ daily for 4 days) diazepam administration are investigated on brain regional 5-hydroxytryptamine (5-HT; serotonin) and 5-hydroxy indoleacetic acid (5-HIAA) concentration in rats. Daily treatment decreased food intakes but body weights did not decrease. Administration of diazepam (1mg/kg) to 4 day sahne injected rats on the 5th day decreased 5-HT levels in the hippocampus and increased it in the hypothalamus. 5-HIAA levels were increased in the striatum and decreased in the hypothalamus. 4 day diazepam injected rats injected with sahne on the 5th day also exhibited silmilar changes of 5-HT and 5-HIAA. Cortical levels of 5-HIAA were also smaller in these rats. Administration of diazepam to 4 day diazepam injected rats again decreased 5-HT in the hippocampus and 5-HIAA in the hypothalamus. 5-HT and 5-HIAA were both decreased in the striatum. Regionally specific effects of diazepam on brain serotonin metabolism are discussed in relation to their possible functions.     

Comparative analysis of EEG spatial organization in the rats with different level of genetically determinated anxiety under ethanol

The pecularities of EEG changes in the rats with geneticaly different level of anxiety was studed after ethanol injection. The biopotentials spatial synchronization and entropy in the "high anxious" rats (strain MR) did not increase under low dose; on the contrary the above changes were characteristic for the rats without anxiety signs (strain MNRA). After injection of middle and high ethanol doses the "high anxious" rats as compared with "low anxious" ones had the "simplification" of reaction type--the increase of narrow frequency coherence (i.e. linear biopotentials relationship) and spectral power of theta-activity (5.75-7.25 Hz), which was combined with the decrease of nonlinear biopotential characteristics. This fact is interpreted as the predominance of subcortical mechanisms of the brain functional state regulation over cortical ones. The significant decrease of high frequency EEG components in "high anxious" rats takes place under more high ethanol doses, presumably reflecting the increase of the anxiolytic level of ethanol effect.     

RO 15-1788 selectively reverses antagonism of pentylenetetrazol-induced discriminative stimuli by benzodiazepines but not by barbiturates

The specificity of ethyl 8-fluro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo (1,5-a) (1,4) benzodiazepine-3-carboxylate (RO 15-1788) in reversing the effectiveness of diazepam and des-methylclobazam, but not of pentobarbital, in antagonizing discriminative stimuli produced by pentylenetetrazol is described. Male hooded rats were trained to discriminate pentylenetetrazol-induced interoceptive discriminative-stimuli (IDS) in a two-lever choice paradigm on an FR10 schedule of food reinforcement. These IDS pharmacologically model verbal report of anxiogenic activity in humans. Diazepam (1,4 benzodiazepine), des-methylclobazam (1,5 benzo-diazepine), and pentobarbital antagonized pentylenetetrazol-IDS. RO 15-1788 neither generalized to nor antagonized pentylenetetrazol-IDS. It also did not cause convulsions in pentylenetetrazol sensitized rats at doses up to 40 mg/kg. It did, however, antagonize the action of diazepam (10 mg/kg) as well as that of des-methylclobazam (160 mg/kg) but not that of pentobarbital. These data suggest that RO 15-1788 is not an anxiomimetic, anxiolytic or a convulsant drug, but it is a specific and effective antagonist of anxiolytic action of benzodiazepines.     

Anxiolytic effect of Kami-Shoyo-San (TJ-24) in mice: possible mediation of neurosteroid synthesis.

We assessed the anxiolytic effect of Kami-Shoyo-San (Jia-wei-xiao-yao-san; TJ-24), one of a traditional Chinese herbal medicine used for the treatment of menopausal anxiety, by the social interaction (SI) test in male mice. Acute administration of TJ-24 (25-100 mg/kg, p.o.), as well as the gamma-amino-butyric acidA/benzodiazepine (GABA(A)/BZP) receptor agonist diazepam (1-3 mg/kg, i.p.), dose dependently increased the SI time, respectively. The GABA(A) receptor antagonist picrotoxin blocked the effects of TJ-24 and diazepam. TJ-24-induced SI behavior was significantly blocked by the GABA(A)/BZP receptor inverse agonist Ro 15-4513 and the GABA(A)/BZP receptor antagonist flumazenil. In addition, 5alpha-reductase inhibitor finasteride potently blocked the effect of TJ-24 without attenuating the basal level by itself. These findings suggest that TJ-24 shows the anxiolytic effect through the neurosteroid synthesis followed by GABA(A)/BDZ receptor stimulations.     

Anxiolytic Properties of New Chemical Entity, 5TIO1

2-[(2,6-dichlorobenzylidene)amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile), 5TIO1, is a new 2-aminothiophene derivative with a promising pharmacological activity. The aim of this work was to evaluate the potential anxiolytic effect of 5TIO1 in animal models. In the elevated plus-maze test, 5TIO1 (0.1, 1.0 and 10.0 mg/kg, i.p) increased the time of permanence and the number of entries in the open arms. In the light/dark box test, 5TIO1 at dose of 0.1 mg/kg (i.p) also showed anxiolytic-like effect indicated by an increase in the time spent in the light box, similar to diazepam 2.0 mg/kg (i.p). 5TIO1 groups did not change locomotor and coordination activities in open field and rotarod tests, respectively, when compared to vehicle. Dose dependent process was not observed and the anxiolytic effects demonstrated were not completely reversed by flumazenil 25 mg/kg (i.p). Our results suggest that 5TIO1 can bind with other receptors, besides the benzodiazepine site of the GABA receptor in mouse brain.     

The phenomenon of one-trial tolerance to the anxiolytic effect of chlordiazepoxide in the elevated plus-maze test is abolished by previous administration of chlordiazepoxide or buspirone

It has been repeatedly reported that the anxiolytic action of benzodiazepines in the elevated plus-maze test is abolished in rats that have received a single prior experience of the test apparatus (one-trial tolerance effect). To analyze whether the one-trial tolerance effect of chlordiazepoxide can be influenced by administration of chlordiazepoxide or buspirone on trial 1, male Wistar rats received an IP injection of vehicle, chlordiazepoxide (8 mg/kg) or buspirone (2.5 mg/kg) 30 min. before testing for 5 min. in the plus-maze (trial 1). Seventy-two hours later, the rats received vehicle or chlordiazepoxide 30 min. before the re-exposure to the plus-maze for 5 min. (trial 2). Groups injected with chlordiazepoxide or buspirone on trial 1 and with chlordiazepoxide on trial 2 showed an anxiolytic effect of chlordiazepoxide on trial 2, as opposed to rats injected with vehicle on trial 1 and with chlordiazepoxide on trial 2. As opposed to previous studies, the present results suggest that the influence of prior experience with the plus-maze on the anxiolytic action of chlordiazepoxide during re-exposure seems to depend critically on the drug state in which trial 1 is experienced. These results are discussed with respect to the hypothesis proposed to explain the phenomenon of one-trial tolerance.