Free radical scavengers suppress the accumulation of platinum in the cerebral cortex

We investigated whether free radical scavengers and antioxidants inhibit the accumulation of platinum (Pt) in the cerebral cortex. Pt was detected in the cerebral cortex of mice afters administration of cisplatin and exposure to short-term hypoxia. When mice were treated with either allopurinol (20 mg/kg) or catalase (100 mg/kg) before cisplatin administration and low oxygen exposure, Pt was not detected in the cerebral cortex. However, Pt was detected in the cerebral cortex of mice pretreated with either a low dosage of allopurinol or heat-denatured catalase. Furthermore, Pt was detected in the cerebral cortex of mice preadministered vitamin C, vitamin E, or deferoxamine. Lipid peroxide levels in the cerebral cortex increased 10 min after the treatment of hypoxia, and peaked 30 min after the treatment. These results suggested that short-term hypoxia produces free radicals, which allows Pt to pass through the blood-brain barrier and accumulate in the cerebral cortex, and that the production of free radicals is reduced by the administration of either allopurinol or catalase, which prevents Pt from passing through the barrier.     

Repeated Administration of γ-VinylGABA Reduces Rat Brain Glutamine Synthetase Activity

Abstract: The glutamine cycle has been proposed as a pathway in which glutamine synthesized in glia provides substrate for synthesis of the neurotransmitters glutamate and GABA as they are lost from neurons. To test whether GABA may regulate this pathway, the effect of elevated GABA on the glial enzyme glutamine synthetase was examined in rat brain. Repeated subcutaneous injections of the antiepileptic GABA transaminase inhibitor γ-vinylGABA at a dose of 150 mg/kg per day for 21 days reduced glutamine synthetase activity by 36% in the cortex and 22% in the cerebellum. At 30 mg/kg per day, glutamine synthetase activity was reduced by 9.5% in the cortex but unchanged in the cerebellum. The reductions were brain specific because the skeletal muscle and liver enzymes were unaffected by γ-vinylGABA administration. Amino acid analysis of the cortex from γ-vinylGABA-treated rats demonstrated a 270% increase in GABA levels after 150 mg/kg but no change after 30 mg/kg. GABA levels and glutamine synthetase activity were inversely correlated. The 150 mg/kg dose significantly lowered cortical glutamine and glutamate levels. The decline in brain glutamine synthetase activity with chronic γ-vinylGABA administration developed gradually over time and may be due to the slow turnover of this enzyme in vivo.     

Valeriana wallichii root extract improves sleep quality and modulates brain monoamine level in rats

The present study was performed to investigate the effects of Valeriana wallichi (VW) aqueous root extract on sleep-wake profile and level of brain monoamines on Sprague-Dawley rats. Electrodes and transmitters were implanted to record EEG and EMG in freely moving condition and the changes were recorded telemetrically after oral administration of VW in the doses of 100, 200 and 300 mg/kg body weight. Sleep latency was decreased and duration of non-rapid eye movement (NREM) sleep was increased in a dose dependent manner. A significant decrease of sleep latency and duration of wakefulness were observed with VW at doses of 200 and 300 mg/kg. Duration of NREM sleep as well as duration of total sleep was increased significantly after treatment with VW at the doses of 200 and 300 mg/kg. VW also increased EEG slow wave activity during NREM sleep at the doses of 200 and 300 mg/kg. Level of norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT) and hydroxy indole acetic acid (HIAA) were measured in frontal cortex and brain stem after VW treatment at the dose of 200mg/kg. NE and 5HT level were decreased significantly in both frontal cortex and brain stem. DA and HIAA level significantly decreased only in cortex. DOPAC level was not changed in any brain region studied. In conclusion it can be said that VW water extract has a sleep quality improving effect which may be dependent upon levels of monoamines in cortex and brainstem.     

Sodium oxybutyrate and piracetam acceleration of the compensatory-reparative processes after damage to the cerebral cortex in rats

The effects of sodium hydroxybutyrate and piracetam on compensatory-reparative processes in the central nervous system have been investigated in rats after extirpation of the frontal cortex. The animals were pretrained to conditioned reflex of active avoidance. Extirpation of the frontal cortex has been shown to disturb the conditioned reflex. Sodium hydroxybutyrate (50 mg/kg) and piracetam (200 mg/kg) were found to precipitate the recovery of the damaged reflexes.     

The evaluation of the efficacy of antihypoxic agents lowering hemoglobin oxygen affinity in acute cerebral ischemia]

Influence of natrii hydroxybutyrate (100 mg/kg), ascorbate (100 mg/kg), cavinton (5 mg/kg), bemitil (50 mg/kg), ethomersol (50 mg/kg) on Hb-O2 affinity and cortex PO2 after both carotid artery occlusion in rats was investigated. Correlation (r-0.87; P less than 0.05) between lowering of Hb-O2 affinity and antihypoxic effect was demonstrated in the line of these drugs.     

Changes in the sensitivity of brain dopamine and serotonin receptors during the prolonged administration of carbidine

Male Wistar rats were treated chronically with either carbidine (10 mg/kg/day) or haloperidol (1 mg/kg/day) for 23 consecutive days. On days 4-5 after the treatment discontinuation the animals were challenged with apomorphine HCl (0.5 mg/kg) or 5-OTP (150 mg/kg i. p) in combination with pargiline (40 mg/kg i. p) and stereotype responses were scored. In carbidine-treated rats the intensity of stereotype sniffings was increased after apomorphine treatment. In contrast, animals treated with haloperidol exhibited more intensive gnawing after apomorphine in comparison to vehicle-treated rats. 5-OTP-induced head twitches were increased only in carbidine-treated rats. Prolonged carbidine treatment in contrast to haloperidol induced a decrease in 5H-spiperone and 3H-LSD binding in the frontal cortex, with the density of D-2 receptors in the striatum practically unchanged. It is concluded that neuroleptic carbidine in contrast to classical neuroleptics has a more selective effect in serotonin (S-2) receptors and antidepressive properties of this compound may be due to the down-regulation of S-2 receptors in the brain.     

Differential alpha-mediated inhibition of dopamine and noradrenaline release in the parietal and occipital cortex following noradrenaline transporter blockade

Parietal and occipital cortices, while densely innervated by noradrenalin 2 (NA) projections, possess a comparatively sparse dopamine 2 (DA) innervation, even sparser than the prefrontal cortex. We previously reported that reboxetine and desipramine, two selective norepinephrine transporter (NET) blockers, at doses that maximally increase DA in the prefrontal cortex, do not increase DA in the parietal and occipital cortices. In the present study, we performed a full dose-response study of the effect of systemic reboxetine and desipramine on DA and NA in dialysates from the parietal and occipital cortices. Seven doses of reboxetine (0.1, 0.25, 0.5, 1.0, 2.5, 5.0 and 10 mg/kg) and four doses of desipramine (0.25, 1.0, 2.5 and 5.0 mg/kg) were tested. Reboxetine and desipramine differentially affected dialysate DA as compared with NA. Reboxetine increased DA maximally by about 100% after doses of 0.25-0.5 mg/kg and showed a bell-shaped dose-response function in both areas; desipramine did not affect DA in the parietal cortex and increased it in the occipital cortex only at 2.5 mg/kg. NA was maximally increased by 275% by 0.5-2.5 mg/kg reboxetine and by about 300% by 5.0 mg/kg desipramine with a more linear dose-response curve. The mechanism of peculiar dose-response function of dialysate DA after reboxetine and desipramine was further investigated by testing the effect of drugs on dialysate DA and NA under alpha(2) receptor blockade. Under local perfusion of the occipital cortex with idazoxan, an otherwise ineffective dose of reboxetine and desipramine (5 mg/kg) became effective in raising extracellular DA. In contrast, the effect of reboxetine on NA was potentiated, while that of desipramine was not affected. These results suggest that, in the parietal and occipital cortices, extracellular NA, raised by NET blockade, exerts a preferential inhibitory influence on DA release by acting on local alpha(2) receptors, thus accounting for the bell-shaped feature of the dose-response function of drugs on dialysate DA in these areas.     

The behavioral and biochemical sequelae of the removal of the olfactory bulbs in C57Bl/6j mice]

Ablation of the olfactory bulbs in mice C57Bl/6j was accompanied by motor and orienting-exploratory activity augmentation in the "open field" test and deterioration of the learning ability to active and passive avoidance. The most expressed behavioural changes developed in four weeks after the surgery. Chronic administration of antidepressants (amitriptyline, 20 mg/kg; trazodone, 20 mg/kg; imipramine, 10 mg/kg; intraperitoneally) normalized behaviour of bulbectomized animals, trazodone being the most effective. In the biochemical studies the brainstem serotonin level was found to be decreased and the density of 5HT2-receptors in the cerebral cortex increased in bulbectomized mice. Only trazodone was able to correct the biochemical indices. The state of the bulbectomized mice is supposed to serve a model of a depression with hypo-function of serotonergic system of the brain.     

Concentrations of elements in rat thymocytes measured by X-ray microanalysis

Summary Elemental concentrations of rat thymocytes in vivo were studied by X-ray microanalysis of freeze-dried sections. Cells from different regions, the subcapsular zone, the cortex and the medulla were studied in thymic tissue from a number of animals. Generally thymocytes situated in the medulla had higher concentrations of K compared to those in the subcapsular zone. The concentration of Na in the nucleus was constant in the medulla in all animals but some variation in this element was seen between animals in the subcapsular zone. The distribution of K/Na ratio in individual thymocytes was different in each region of the thymus. Cells with low K/Na ratio (<5) were predominant in the subcapsular zone, whereas cells with higher values for K/Na ratio were found in the cortex and medulla. The subcapsular zone is the region where mitotic cells are mostly situated. The finding of thymocytes with higher concentrations of Na and low K/Na ratios in this region is in accord with in vitro studies on thymocyte stimulation.     

Changes in Antioxidant Defense Enzymes after d-amphetamine Exposure: Implications as an Animal Model of Mania

Studies have demonstrated that oxidative stress is associated with amphetamine-induced neurotoxicity, but little is known about the adaptations of antioxidant enzymes in the brain after amphetamine exposure. We studied the effects of acute and chronic amphetamine administration on superoxide dismutase (SOD) and catalase (CAT) activity, in a rodent model of mania. Male Wistar rats received either a single IP injection of d-amphetamine (1 mg/kg, 2 mg/kg, or 4 mg/kg) or vehicle (acute treatment). In the chronic treatment rats received a daily IP injection of either d-amphetamine (1 mg/kg, 2 mg/kg, or 4 mg/kg) or vehicle for 7 days. Locomotor behavior was assessed using the open field test. SOD and CAT activities were measured in the prefrontal cortex, hippocampus, and striatum. Acute and to a greater extent chronic amphetamine treatment increased locomotor behavior and affected SOD and CAT activities in the prefrontal cortex, hippocampus and striatum. Our findings suggest that amphetamine exposure is associated with an imbalance between SOD and CAT activity in the prefrontal cortex, hippocampus and striatum.     

Studies on the Formation of 6-Hydroxydopamine in Mouse Brain After Administration of 2,4,5-Trihydroxyphenylalanine (6-HydroxyDOPA)

2,4,5-Trihydroxyphenylalanine (6-OH-DOPA) destroys central and peripheral noradrenergic neurons, while sparing dopaminergic neurons. Previous studies indicate that 6-OH-DOPA toxicity is mediated by the formation of 6-hydroxydopamine. However, levels of 6-hydroxydopamine in brain following peripheral administration of 6-OH-DOPA have not been documented. In the current study, 6-OH-DOPA and 6-hydroxydopamine were measured in brain by HPLC with electrochemical detection after intraperitoneal injection of 6-OH-DOPA. When mice were injected with 100 mg 6-OH-DOPA/kg, 6-hydroxydopamine levels in the striatum were highest (1.9 microgram/g) at 15 min and fell slowly to 24% of the peak value at 4 h. Experiments with reserpine indicated that the relatively stability of 6-hydroxydopamine was largely dependent upon storage in synaptic vesicles. Reserpine (10 mg/kg) lowered striatal 6-hydroxydopamine levels to 21.6% of control (non-reserpine-treated) values at 1 h, and to 8.9% of control values at 4 h. Levels of 6-hydroxydopamine in the striatum at 1 h were increased 113% by pargyline (100 mg/kg), 145% by alpha-methyldopahydrazine (carbidopa; 25 mg/kg), and 261% by pargyline and carbidopa together. Levels of dopamine in the striatum were unchanged at 2.5 h after 200 mg 6-OH-DOPA/kg (with pargyline and 50 mg carbidopa/kg), whereas levels of norepinephrine in the frontal cortex fell by 77%. At the same time, 6-hydroxydopamine levels were 8.8-fold higher in the striatum (5.54 micrograms/g) than in the cortex (0.63 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)     

Citrate synthase activity increases in homogenates of the cerebral cortex from rats treated with the convulsant 3-mercaptopropionic acid

The administration of the convulsant 3-mercaptopropionic acid (150 mg/kg i.p.) increased the respiratory capacity of mitochondria isolated from rat cerebral cortex. This increase was observed when pyruvate-malate were used as substrates, but oxygen uptake was not activated with succinate, glutamate-malate or α-ketoglutarate. Citrate synthase activity in rat brain homogenates increased (about 40%) after the administration of convulsant doses of 3-mercaptopropionic acid (50 and 150 mg/kg). This effect was found after seizures but not during seizures or after a dose that did not produce convulsions (20 mg/kg). The enhancement of citrate synthase activity was observed at various oxaloacetate concentrations, with an increase in V_max. The enhancement was still evident after incubation and removal of the soluble phase by centrifugation, but not after freeze-thawing.     

反复摄取烟碱对脑肌醇含量的影响

急性实验中,间隔５ｍｉｎ反复注射烟碱０．５,１．０,１．０,２．０,２．０ｍｇ／ｋｇｉｐ,３０ｍｉｎ后大鼠大脑皮层及海马中肌醇含量升高,但纹状体中肌醇含量无显著变化;相同条件下,氯化锂１０ｍｍｏｌ／ｋｇｉｐ３０ｍｉｎ后大脑皮层和海马中肌醇含量显著降低;慢性实验中,烟碱２．０－１０．０ｍｇ／ｋｇｓｃｂｉｄ１４ｄ后,大鼠大脑皮层中肌醇含量显著增高;烟碱２．６９－１１．５３ｍｇ／ｋｇ／ｄｐｏ６４ｄ后,大鼠大脑皮层中肌醇含量也显著增高。表明烟碱的作用不同于氯化锂,反复给予烟碱可使大鼠大脑皮层中肌醇含量增加。     

Activation of Melatonin Receptor Sites Retarded the Depletion of Norepinephrine Following Inhibition of Synthesis in the C3H/HeN Mouse Hypothalamus

The aim of the present study was to determine the effect of activation of melatonin receptor sites on the activity of noradrenergic neurons in the C3H/HeN mouse brain. Changes in noradrenergic activity were assessed by measuring norepinephrine (NE) levels in the hypothalamus, frontal cortex, and hippocampus following inhibition of NE synthesis with alpha-methyl-p-tyrosine (alpha-MpT) (300 mg/kg, i.p., 2 h). 6-Chloromelatonin (1-30 mg/kg, i.p.) significantly retarded the alpha-MpT-induced decrease in NE levels in the hypothalamus, but not in hippocampus and frontal cortex. This effect was observed at 30 min and 60 min after 6-chloromelatonin administration and was dose dependent. At noon, when the levels of endogenous melatonin are low, the melatonin receptor antagonist luzindole (30 mg/kg, i.p., 30 min) did not affect the depletion of NE by alpha-MpT; however, it (1-30 mg/kg) completely antagonized the 6-chloromelatonin-induced reduction of NE depletion elicited by alpha-MpT in hypothalamus. These results suggest that activation of melatonin receptor sites in brain of C3H/HeN mouse retarded the depletion of NE elicited by alpha-MpT. At midnight, when the levels of melatonin are high, luzindole (30 mg/kg) significantly accelerated the depletion of NE by alpha-MpT in hypothalamus, but not in frontal cortex or hippocampus, suggesting activation of melatonin receptor sites by endogenous melatonin. We conclude that activation of melatonin receptor sites in C3H/HeN mouse brain by endogenous melatonin inhibits the activity of noradrenergic neurons innervating the hypothalamus.     

The nNOS inhibitor,AR-R17477AR,prevents the loss of NF68 immunoreactivity induced by methamphetamine in the mouse striatum

The present study examined the time-course and regionally-selective changes in the levels of the neurofilament protein NF68 in the mouse brain induced by methamphetamine (METH). The ability of low ambient temperature, or of the specific neuronal nitric oxide synthase (nNOS) inhibitor AR-R17477AR, to protect against both long-term striatal NF68 and dopamine loss induced by METH (3 mg/kg, i.p.) was also studied. Seven days after METH administration (3, 6 and 9 mg/kg, i.p., three times at 3 h intervals), mice showed a reduction of about 40% in immunoreactivity for NF68 in the striatum. This effect was not produced in cortex after METH administration at the dose of 3 mg/kg. No difference from controls was observed when measurements were carried out 1 h and 24 h after the last METH injection at the dose of 3 mg/kg. The loss of NF68 immunoreactivity seems to be associated with the long-term dopamine depletion induced by METH, since no change in serotonin concentration is observed in either the striatum or cortex 7 days after dosing. Animals kept at a room temperature of 4 degrees C showed a loss of NF68 similar to those treated at 22 degrees C but an attenuation of dopamine depletion in the striatum. Pre-treatment with AR-R17477AR (5 mg/kg, s.c.) 30 min before each of the three METH (3 mg/kg, i.p.) injections provided complete protection against METH-induced loss of NF68 immunoreactivity and attenuated the decrease in striatal dopamine and HVA concentrations by about 50%. These data indicate that both the reduction of NF68 immunoreactivity and the loss of dopamine concentration are due to an oxidative stress process mediated by reactive nitrogen species, and are not due to changes in body temperature.     

THE CONVULSANT ACTION OF HYDRAZIDES AND REGIONAL CHANGES IN CEREBRAL γ-AMINOBUTYRIC ACID AND PYRIDOXAL PHOSPHATE CONCENTRATIONS

Abstract— Regional changes in the concentration of GABA and pyridoxal phosphate were determined in rat brain after i.p. administration of convulsant doses of methyldithiocarbazinate (11 mg/kg), isonicotinic acid hydrazide (250 mg/kg) and thiosemicarbazide (25 mg/kg). At 15 and 30 min after methyldithiocarbazinate GABA concentrations were reduced in all brain regions (except ventral mid-brain). After 30 min the largest decrease was in the cerebellum (41%) and the smallest decrease in the hypothalamus (20%). Pyridoxal phosphate concentrations were decreased by 39-57%. After isonicotinic acid hydrazide. the regional decreases in GABA concentration were smaller and of slower onset than those seen after methyldithiocarbazinate. The pons-medulla was the first region to show a decrease (at 15 min) whereas a decrease was not seen in the frontal cortex until 45 min. Regional decreases in pyridoxal phosphate were smaller than those seen after methyldithiocarbazinate. After thiosemicarbazide, small regional decreases in GABA concentration were observed only in the hypothalamus, cerebellum, pons-medulla and posterior cortex (13-18%) and there was no apparent correlation between regional decreases in pyridoxal phosphate and regional decreases in GABA.     

Difference in the effects of the antidepressant tianeptine on dopaminergic metabolism in the prefrontal cortex and the nucleus accumbens of the rat. A voltammetric study

The effects of the new tricyclic antidepressant tianeptine were investigated on dopaminergic (DAergic) metabolism in the anteromedian prefrontal cortex and the nucleus accumbens of the rat. DAergic metabolism was assessed by the measurement of DOPAC, the main presynaptic metabolite of dopamine, using in vivo voltammetry in rats ventilated with halothane (0.5-0.75% in air). Acute treatment with tianeptine (10 mg/kg, 20 mg/kg) only increased significantly DOPAC levels in the anteromedian prefrontal cortex. After chronic treatment with tianeptine (15 days, 2 times/day) the increases in DOPAC levels in this structure were altered and less pronounced with the 20 mg/kg dose. Previous studies led to suggest that both acute and chronic effects on DAergic terminals in the anteromedian prefrontal cortex may be involved in the therapeutic action of this new antidepressant.     

Acute Cocaine Increases Interleukin-1�� mRNA and Immunoreactive Cells in the Cortex and Nucleus Accumbens

The cytokine, interleukin-1β (IL1β) is a sleep regulatory substance whose expression is enhanced in response to neuronal stimulation. In this study, IL1β mRNA and immunoreactivity (IR) are evaluated after acute cocaine. First, IL1β mRNA levels were measured at the start or end of the light period after saline or acute exposure to a low dose of cocaine (5 mg/kg, intraperitoneal (ip)). IL1β mRNA levels after an acute exposure to cocaine (5 mg/kg, ip) at dark onset were significantly higher than those obtained from rats sacrificed after an acute exposure to saline in the piriform and somatosensory cortex, and nucleus accumbens. Acute exposure of cocaine at 5 mg/kg at dark onset also increased the number of IL1β-immunoreactive astrocytes in layer I-V of the prefrontal cortex, somatosensory cortex and nucleus accumbens. These data suggest that IL1β mRNA and protein levels in some of the dopaminergically innervated brain regions are responsive to cocaine.     

Effects of the Histamine H3-Agonist (R)-α-Methylhistamine and the Antagonist Thioperamide on Histamine Metabolism in the Mouse and Rat Brain

To study the feedback control by histamine (HA) H3-receptors on the synthesis and release of HA at nerve endings in the brain, the effects of a potent and selective H3-agonist, (R)-alpha-methylhistamine, and an H3-antagonist, thioperamide, on the pargyline-induced accumulation of tele-methylhistamine (t-MH) in the brain of mice and rats were examined in vivo. (R)-alpha-Methylhistamine dihydrochloride (6.3 mg free base/kg, i.p.) and thioperamide (2 mg/kg, i.p.), respectively, significantly decreased and increased the steady-state t-MH level in the mouse brain, whereas these compounds produced no significant changes in the HA level. When administered to mice immediately after pargyline (65 mg/kg, i.p.), (R)-alpha-methylhistamine (3.2 mg/kg, i.p.) inhibited the pargyline-induced increase in the t-MH level almost completely during the first 2 h after treatment. Thioperamide (2 mg/kg, i.p.) enhanced the pargyline-induced t-MH accumulation by approximately 70% 1 and 2 h after treatment. Lower doses of (R)-alpha-methylhistamine (1.3 mg/kg) and thioperamide (1 mg/kg) induced significant changes in the pargyline-induced t-MH accumulation in the mouse brain. In the rat, (R)-alpha-methylhistamine (3.2 mg/kg, i.p.) and thioperamide (2 mg/kg, i.p.) also affected the pargyline-induced t-MH accumulation in eight brain regions and the effects were especially marked in the cerebral cortex and amygdala. These results indicate that these compounds have potent effects on HA turnover in vivo in the brain.     

Benzodiazepine Receptor Binding of Triazolobenzodiazepines In Vivo: Increased Receptor Number with Low-Dose Alprazolam

Abstract: Triazolobenzodiazepines are in clinical use as hypnotics and anxiolytics. We analyzed in vivo receptor binding and brain concentrations of alprazolam, triazolam, and estazolam. Drug concentrations measured in the cerebral cortex 1 h after administration were directly proportional to dose for all three compounds. In vivo receptor binding, as defined by the specific uptake of [³H]Ro 15–1788, decreased with increasing doses of estazolam and triazolam, a finding indicating dose-related increases in receptor occupancy due to these compounds. Triazolam was substantially more potent, with an IC₅₀ value of 16 ng/g, compared with 117 ng/g for estazolam. At higher doses of alprazolam (>0.2 mg/kg), receptor binding by [³H]Ro 15–1788 likewise decreased with increasing dose of the former drug. However, at lower doses of alprazolam (0.02–0.05 mg/kg), which resulted in cortex concentrations of 2–7 ng/g, receptor binding was increased above control values in cortex, hypothalamus, and hippocampus but not in several other brain regions. Binding returned to control values at doses of ≤0.01 mg/kg. Similar results were obtained in time course studies. At 8 and 10 h after a dose of 1 mg/kg i.p., corresponding to cortex concentrations of 2.7–7 ng/g, receptor binding was increased compared with controls. Similarly, at 1, 2, and 3 h after a single dose of 0.05 mg/kg, corresponding to cortex concentrations of 3.7–5.8 ng/g, receptor binding was also increased. The apparent affinity of benzodiazepine receptors for clonazepam in mice receiving alprazolam (0.05 mg/kg) was unchanged from that in untreated control mice, an observation suggesting that low doses of alprazolam increased receptor number. The brain concentration vs. receptor occupancy relationships for triazolam and estazolam resemble those for other benzodiaze-pines, but alprazolam appears to be anomalous in that low brain concentrations increase benzodiazepine receptor number.