Number Of Closed Arm Entries Research Articles

Study of the effect of extract of Thymus vulgaris on anxiety in male rats

There is some evidence in traditional medicine for the effectiveness of Thymus vulgaris (百里香 bǎi lǐ xiāng) in the treatment of anxiety in humans. The elevated plus-maze (EPM) has broadly been used to investigate anxiolytic and anxiogenic compounds. The present study investigated the effects of extract of T. vulgaris on rat behavior in the EPM. In the present study, the data were obtained from male Wistar rats. Animals were divided into four groups: saline group and T. vulgaris groups (50 mg/kg, 100 mg/kg, and 200 mg/kg infusion for 7 days by feeding). During the test period, the total distance covered by animals, the number of open- and closed-arm entries, and the time spent in open and closed arms of the EPM were recorded. T. vulgaris increased open-arm exploration and open-arm entry in the EPM, whereas extract of this plant has no effects on the total distance covered by animals and the number of closed-arm entries. The results of the present experiment indicate that T. vulgaris may have an anxiolytic profile in rat behavior in the EPM test, which is not influenced by the locomotor activity. Further research is required to determine the mechanisms by which T. vulgaris extract exerts an anxiolytic effect in rats.

Long-lasting effects of inescapable-predator stress on brain tryptophan metabolism and the behavior of juvenile mice

The kynurenine (KYN) pathway, which is initiated by indoleamine 2,3-dioxygenase, is the main tryptophan (TRP) metabolic pathway. It shares TRP with the serotonin (5-HT) pathway. We investigated the influence of inescapable-predator (rat) stress on behavior and brain TRP metabolism in mice. Male ICR mice (4W) were exposed to 20-min inescapable-predator stress. Behavior on an elevated plus-maze, and TRP, KYN, and 5-HT levels in the prefrontal cortex, hippocampus, amygdala, and dorsal raphe nuclei were measured 1 and 4 weeks after stress exposure. Predator stress increased the number of open-arm entries (NOA) 4 weeks after stress exposure without altering the number of closed-arm entries (NCA). Thus, the open/closed-arm entry ratio (NOA/NCA) increased after stress exposure. Predator stress increased KYN levels in the prefrontal cortex (until 4 weeks after stress exposure) and dorsal raphe nuclei (for 1 week after stress exposure), decreased 5-HT levels in all brain regions (until 4 weeks after stress exposure). Thus, predator stress increased the KYN/5-HT ratio in all regions, in particular in the prefrontal cortex and hippocampus until 4 weeks after stress exposure. Predator stress shifted the balance between the KYN and 5-HT pathways to the KYN pathway, and induced behavioral disinhibition.

Previous spatial learning is required for the development of place preference in rats following chronic administration of and withdrawal from morphine

The positive reinforcing properties of addictive drugs have a primary role in the development of drug dependence. In the field of opiates, great attention has been given to this phenomenon, as well as to the negative properties eliciting craving and inducing relapse during withdrawal. This study was designed to evaluate whether elevated plus-maze (EPM) experienced rats withdrawn from low doses of subcutaneous (s.c.) morphine (10 mg/kg), in which a high anxiety level is the most prominent withdrawal symptom, acquire place preference when submitted to a conflict paradigm in which drug effects are paired with an aversive context: the distal part of the open arms of an EPM. Both the anxiety test and place preference conditioning were measured in the same apparatus, a biased version of the plus-maze. In order to verify the influence of previous EPM spatial learning on the performance of morphine-withdrawn rats, half the animals in this study experienced the EPM prior to treatment. Additional groups were also tested under the influence of morphine effects. The effects of the treatments were quantified through the analysis of three types of measures: anxiety was inferred from the use of the conventional measures (percentage of entries and time spent in the open-arms) and risk-assessment behaviours (frequency of stretched-attending postures - SAP, and time spent at the centre of the maze). Place preference conditioning was evaluated through analysis of the number of entries, total time spent and distance run in the open-arm extremities, which is where the animals were conditioned. The number of closed-arm entries was taken as an index of locomotor activity. Our results showed that (i) EPM naïve rats pre-treated with morphine did not develop place preference, behaving like control rats; (ii) rats that had previous experience in the EPM showed no changes in open-arm avoidance on the second exposure, when compared with rats naïve for this condition; (iii) previous spatial learning of the EPM contextual cues was, in fact, a requirement for anxiety-inducing place preference for the open-arms in morphine-withdrawn rats and, (iiii) conditioned place preference was achieved both in rats under the effects of morphine and in withdrawal, probably through the influence of the positive or negative reinforcing effects promoted by the presence or absence of the drug in the central nervous system.

Previous spatial learning is required for the development of place preference in rats following chronic administration of and withdrawal from morphine.

The positive reinforcing properties of addictive drugs have a primary role in the development of drug dependence. In the field of opiates, great attention has been given to this phenomenon, as well as to the negative properties eliciting craving and inducing relapse during withdrawal. This study was designed to evaluate whether elevated plus-maze (EPM) experienced rats withdrawn from low doses of subcutaneous (s.c.) morphine (10 mg/kg), in which a high anxiety level is the most prominent withdrawal symptom, acquire place preference when submitted to a conflict paradigm in which drug effects are paired with an aversive context: the distal part of the open arms of an EPM. Both the anxiety test and place preference conditioning were measured in the same apparatus, a biased version of the plus-maze. In order to verify the influence of previous EPM spatial learning on the performance of morphine-withdrawn rats, half the animals in this study experienced the EPM prior to treatment. Additional groups were also tested under the influence of morphine effects. The effects of the treatments were quantified through the analysis of three types of measures: anxiety was inferred from the use of the conventional measures (percentage of entries and time spent in the open-arms) and risk-assessment behaviours (frequency of stretched-attending postures - SAP, and time spent at the centre of the maze). Place preference conditioning was evaluated through analysis of the number of entries, total time spent and distance run in the open-arm extremities, which is where the animals were conditioned. The number of closed-arm entries was taken as an index of locomotor activity. Our results showed that (i) EPM naive rats pre-treated with morphine did not develop place preference, behaving like control rats; (ii) rats that had previous experience in the EPM showed no changes in open-arm avoidance on the second exposure, when compared with rats naive for this condition; (iii) previous spatial learning of the EPM contextual cues was, in fact, a requirement for anxiety-inducing place preference for the open-arms in morphine-withdrawn rats and, (iiii) conditioned place preference was achieved both in rats under the effects of morphine and in withdrawal, probably through the influence of the positive or negative reinforcing effects promoted by the presence or absence of the drug in the central nervous system.

Neonatal administration of fluoxetine did not alter the anxiety indicators, but decreased the locomotor activity in adult rats in the elevated plus-maze

The objective of this study was evaluate the anxiety and locomotor activity (LA) in 52 Wistar adult male rats, being 26 treated with fluoxetine (10 mg/Kg - sc) in the neonatal period. These same rats received foot shock (FS) (1.6-mA - 2-s) in the 90th day. The anxiety and LA were appraised by plus-maze. The time spent in the open arms was used as anxiety index and the LA was measured by number of entries in closed arms (NECA) and the total of entries (TE). T-test was used with p<0.05 and expresses data in mean+/-SEM. There were reductions with the fluoxetine group in the NECA (2.35+/-0.33) and in the TE (3.96+/-0.61) compared to the controls (4.65+/-0.52) and (6.96+/-0.94). The neonatal administration of fluoxetine did not alter the anxiety, but reduced the LA in the animals that received FS.