Anxiolytic-like Effect Of Diazepam Research Articles

In vivo knockdown of GAD67 in the amygdala disrupts fear extinction and the anxiolytic-like effect of diazepam in mice

In mammals, γ-aminobutyric acid (GABA) transmission in the amygdala is particularly important for controlling levels of fear and anxiety. Most GABA synthesis in the brain is catalyzed in inhibitory neurons from ℒ-glutamic acid by the enzyme glutamic acid decarboxylase 67 (GAD67). In the current study, we sought to examine the acquisition and extinction of conditioned fear in mice with knocked down expression of the GABA synthesizing enzyme GAD67 in the amygdala using a lentiviral-based (LV) RNA interference strategy to locally induce loss-of-function. In vitro experiments revealed that our LV-siRNA-GAD67 construct diminished the expression of GAD67 as determined with western blot and fluorescent immunocytochemical analyses. In vivo experiments, in which male C57BL/6J mice received bilateral amygdala microinjections, revealed that LV-siRNA-GAD67 injections produce significant inhibition of endogenous GAD67 when compared with control injections. In contrast, no significant changes in GAD65 expression were detected in the amygdala, validating the specificity of LV knockdown. Behavioral experiments showed that LV knockdown of GAD67 results in a deficit in the extinction, but not the acquisition or retention, of fear as measured by conditioned freezing. GAD67 knockdown did not affect baseline locomotion or basal measures of anxiety as measured in open field apparatus. However, diminished GAD67 in the amygdala blunted the anxiolytic-like effect of diazepam (1.5 mg kg–1) as measured in the elevated plus maze. Together, these studies suggest that of GABAergic transmission in amygdala mediates the inhibition of conditioned fear and the anxiolytic-like effect of diazepam in adult mice.

Parallel anxiolytic-like and antinociceptive actions of diazepam in the anterior basolateral amygdala and dorsal periaqueductal gray

Rationale: The antinociceptive actions of diazepam and other benzodiazepines are partly due to their anxiolytic-like properties. Objective: This study was conducted to analyze the relationship between the anxiolytic-like and antinociceptive effects of diazepam when injected into the anterior basolateral amygdala (ABLA) and the dorsal periaqueductal gray (dPAG). These areas were selected because of their important participation in the regulation of anxiety and defensive responses. Methods: The anxiolytic-like effect of diazepam was evaluated with the rat burying behaviour test. The pain-induced functional impairment in the rat (PIFIR) model was used to study the effects of diazepam on nociception. Nociception was induced by intra-articular injection of 15% uric acid into the knee joint of the right hind limb. Results: Sole exposure to the burying behaviour test produced a slight non-significant hyperalgesic effect. Diazepam injection (2.0 μg/0.4 μl) into the ABLA or dPAG produced a reduction in cumulative burying behaviour – an anxiolytic-like effect – together with an increase in burying behaviour latency. Such reduced experimental anxiety was paralleled by an antinociceptive response (i.e., increased use of the uric-acid-injected limb). Reduced experimental anxiety was correlated with antinociception after diazepam infusion into both brain structures. Conclusions: Diazepam-reduced experimental anxiety was paralleled by antinociceptive effects.

Gestational manganese intoxication and anxiolytic-like effects of diazepam and the 5-HT1A receptor agonist 8-OH-DPAT in male Wistar rats

In the present study, the effects of prenatal manganese (Mn) intoxication on the anxiolytic-like effects of diazepam and the 5-HT1A receptor agonist R-(+)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT) were examined. Wistar dams were exposed to MnCl2•4H2O at 5, 000 ppm in the drinking water for the duration of pregnancy. On the day of parturition, Mn was discontinued as an additive in the drinking water. Control rats were derived from dams that consumed tap water and had no exposure to Mn. Male offspring were tested at the age of 12 weeks. The anxiolytic-like effect was assessed in an elevated plus maze device and with the Vogel conflict test. The benzodiazepine anxiolytic diazepam (5mg/kg, ip) increased the percentage of time spent in open arms in control rats (in comparison to saline treatment) (p<0.05); no such effect was seen in Mn-exposed rats. Conversely, the serotoninergic 5-HT1A agonist 8-OH-DPAT (0.3mg/kg, ip) increased the percentage of time spent in open arms in both experimental groups. In the Vogel drinking test, an anxiolytic-like effect was also observed in both test groups (in controls this was of borderline significance). In contrast, 8-OH-DPAT did not evoke an anxiolytic-like action in control or in Mn-exposed rats in the anticonflict test. In conclusion, findings indicate that gestational Mn exposure attenuated benzodiazepine-mediated anxiolytic-like effects but not those of the 5-HT1A receptor agonist 8-OH-DPAT.

Temporal parameters of one-trial tolerance to benzodiazepines in four-plate test–retest

Anxiolytic-like effect of diazepam is abolished by a previous exposure to four-plate test (FPT). Variations of temporal parameters: interval between trials and duration of Trial 1, with or without electric punishments allow characterizing factors which are responsible for this loss phenomenon. Complete spatial representation of FPT seems to be responsible of this one-trial tolerance, and needs at least a 30 s exposure to the apparatus to be completed, with or without punishments.

A schizophrenia-related sensorimotor deficit links α3-containing GABA A receptors to a dopamine hyperfunction

Overactivity of the dopaminergic system in the brain is considered to be a contributing factor to the development and symptomatology of schizophrenia. Therefore, the GABAergic control of dopamine functions was assessed by disrupting the gene encoding the alpha3 subunit of the GABA(A) receptor. alpha3 knockout (alpha3KO) mice exhibited neither an obvious developmental defect nor apparent morphological brain abnormalities, and there was no evidence for compensatory up-regulation of other major GABA(A)-receptor subunits. Anxiety-related behavior in the elevated-plus-maze test was undisturbed, and the anxiolytic-like effect of diazepam, which is mediated by alpha2-containing GABA(A) receptors, was preserved. As a result of the loss of alpha3 GABA(A) receptors, the GABA-induced whole-cell current recorded from midbrain dopamine neurons was significantly reduced. Spontaneous locomotor activity was slightly elevated in alpha3KO mice. Most notably, prepulse inhibition of the acoustic startle reflex was markedly attenuated in the alpha3KO mice, pointing to a deficit in sensorimotor information processing. This deficit was completely normalized by treatment with the antipsychotic D2-receptor antagonist haloperidol. The amphetamine-induced hyperlocomotion was not altered in alpha3KO mice compared with WT mice. These results suggest that the absence of alpha3-subunit-containing GABA(A) receptors induces a hyperdopaminergic phenotype, including a severe deficit in sensorimotor gating, a common feature among psychiatric conditions, including schizophrenia. Hence, agonists acting at alpha3-containing GABA(A) receptors may constitute an avenue for an effective treatment of sensorimotor-gating deficits in various psychiatric conditions.

Influence of inflammatory nociception on the anxiolytic-like effect of diazepam and buspirone in rats

The effect of anxiety on nociception has been evaluated but not that of nociception on anxiety. The study was conducted to analyse the influence of nociception on basal levels of anxiety-like behaviour and on the action of anxiolytic drugs. Nociception was induced by an intra-articular injection of uric acid at 3.75 or 7.5%. Experimental anxiety was determined in the rat burying behaviour and the elevated plus maze tests. To separate specific anxiety-related drug actions, a spontaneous ambulatory test was included. The anxiolytics, buspirone (2.5 and 5.0 mg/kg, i.p.) and diazepam (0.5, 1.0 and 2.0 mg/kg, i.p.), were used. In the nociception test, the pain-induced functional impairment rat model, uric acid at 3.75 and 7.5% had an effect of around 35 and 75%, respectively. Uric acid (UA) at the lower dose (3.75%) lacked an effect on burying behaviour but significantly increased the time spent and number of entries to the open arms; the higher UA dose (7.5%) produced a significant increase in the time spent and number of entries to the open arms and a statistically significant reduction in cumulative burying. Diazepam and buspirone produced a clear dose-dependent reduction in cumulative burying. In the plus maze, diazepam also induced an increase in the time spent and number of entries to the open arms. In the burying behaviour test, rats with a mild level of nociception (uric acid at 7.5%) were insensitive to the anxiolytic-like effect of these anxiolytic drugs. In the plus maze test, the anxiolytic-like effect of diazepam (1.0 mg/kg) was blocked under both levels of nociception. These data demonstrate that nociception modifies the response to anxiolytic drugs. The role of factors with anxiogenic properties produced during inflammation, which may modify diazepam and buspirone effects, is discussed.

Orchidectomy sensitizes male rats to the action of diazepam on burying behavior latency: role of testosterone

The anxiolytic-like effect of diazepam (0.0, 0.5, 1.0 mg/kg) on the cumulative burying behavior and the burying behavior latency were compared between intact and castrated male rats. In both groups a clear reduction in cumulative burying, denoting an anxiolytic-like response, was observed. However, castrated males were more sensitive to diazepam in the burying behavior latency, a parameter indicating reactivity. Thus, orchidectomized males showed an increase in burying behavior latency after 1.0 mg/kg diazepam treatment. This dose has no effect on burying behavior latency in intact animals. The higher sensitivity to diazepam on reactivity seems to be androgen dependent because it was reversed by chronic treatment with testosterone propionate (TP, 0.0625 mg/rat for 2 weeks). TP (0.0, 0.0625, 0.125, 0.25, 0.5 and 1.0 mg/rat) produced a dose-dependent reduction in burying behavior after chronic treatment (four injections separated 48 h). At no dose did TP affect burying behavior latency. These results indicate that some actions of diazepam vary in males depending upon the endocrine milieu. Results also support the idea of androgens possessing anxiolytic-like actions.