Attenuation of 8-OH-DPAT-induced decreases in 5-Ht synthesis in brain regions of rats adapted to a repeated stress schedule.
ABSTRACT Previously it has been shown that single episode of 2 h restraint produced behavioral deficits in rats which were not observed following daily restraint period of 2h/day for 5 days. It was suggested that adaptation to a stress schedule develops when the similar stress is administered repeatedly. In view of a role of 5-hydroxytryptamine (5-HT) in adaptation to stress the present study concerns effects of a 5-HT-1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) on the synthesis of 5-HT in brain regions of rats adapted to a repeated restraint stress schedule of 2h/day for 5 days. The drug injected systemically at a dose of 1 mg/kg decreased 5-HT synthesis in the hypothalamus, cortex, hippocampus, striatum and raphe regions of previously unrestrained rats. These decreases were either smaller (raphe) or not observed (hypothalamus, cortex and hippocampus) in most brain regions of rats adapted to the repeated restraint stress schedule of 2h/day for 5 days. These results suggest that a subsensitive negative feedback effect on the synthesis of 5-HT leading to an increase in synaptic 5-HT concentration might help coping with stress demand to produce adaptation to stress.
- SourceAvailable from: Bushra Jabeen Mehdi
Dataset: paper 2008
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ABSTRACT: Leptin, originally identified as an anti-obesity hormone, also has an important role in the regulation of mood and emotion. The present study was designed to monitor effects of injected leptin on immobilization stress-induced anorexia, behavioral deficits and plasma corticosterone secretion in rats. Exposure to 2h immobilization stress decreased food intake and body weight in saline injected animals. Animals exposed to open field, elevated plus maze and light dark transition tests the day following immobilization exhibited anxiety-like behavior. Leptin injected at doses of 0.1 and 0.5 mg/kg also decreased food intake and body weight in unstressed animals and elicited anxiolytic effects at dose of 0.5 mg/kg, monitored on the following day. Immobilization -induced decreases in food intake, body weight, as well as stress-induced behavioral deficits in the open field, elevated plus maze and light dark transition test were reversed by exogenous leptin in a dose dependent (0.1-0.5mg/kg) manner. Acute exposure to 2h immobilization produced a four-fold rise in plasma levels of corticosterone. Animals injected with leptin at a dose of 0.1mg/kg, but not at dose of 0.5 mg/kg exhibited a marginal increase in plasma corticosterone. Immobilization-induced increases of plasma corticosterone were reversed by leptin injected at doses of 0.1mg/kg or 0.5 mg/kg. The data suggest that exogenous leptin can reduce stress perception, resulting in an inhibition of stress effects on the activity of hypothalamic-pituitary-adrenal (HPA) axis and behavior. The reported pharmacological effects of leptin represent an innovative approach for the treatment of stress-related disorders.Stress (Amsterdam, Netherlands) 10/2012; · 3.21 Impact Factor
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ABSTRACT: Stress increases vulnerability to addiction while drugs of abuse impair coping responses to predispose to depression. Preclinical research shows that stress exposure augments locomotor sensitization effects of drugs of abuse and impairs behavioral tolerance to repeated stress. The present study investigates relationship between behavioral tolerance to repeated immobilization stress and apomorphine-induced sensitization. Apomorphine was injected either before exposure or after the termination of immobilization, daily for 5days, to monitor drug-induced behavioral sensitization and tolerance in immobilization stress-induced anorexia. We find that apomorphine-induced sensitization is enhanced and tolerance to repeated immobilization impaired if the drug is administered before exposure to stress episode. Conversely, apomorphine-induced sensitization is inhibited and adaptation to stress facilitated if the drug is administered after the termination of stress episode. It shows that apomorphine if experienced during stress produces greater sensitization and impairs stress tolerance. Conversely, sensitization effects of apomorphine are blocked and tolerance to stress facilitated in animals receiving drug after the termination of stress episode. It is suggested that additive effects of stress and apomorphine on mesocorticolimbic dopamine neurotransmission and 5-HT-1A influences on dopamine neurotransmission may have a role in the modulation of apomorphine sensitization and tolerance to repeated immobilization stress. The results may help develop potential pharmacotherapies when substance abuse/ dependence disorder and depression occur together.Pharmacology Biochemistry and Behavior 09/2013; · 2.82 Impact Factor