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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Changes in levels of extracellular noradrenaline (NA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindole-3-acetic acid (5-HIAA) in the frontal cortex, induced by exposure of unrestrained, conscious rats to novel environments, were compared using in vivo microdialysis. NA efflux increased when rats were transferred to a novel cage, but this was not significant when compared with either basal efflux or with changes after equivalent handling in their home cage. Increasing the intensity of illumination of the novel cage by fivefold significantly increased NA efflux with respect to basal efflux but not handled controls. However, a sustained and significant increase in NA efflux (cf. basal efflux or handled controls) was found when an unfamiliar conspecific was also present in the novel cage. In all cases, basal efflux was restored within 1 h of returning rats to their home cage. Neither handling nor environmental stimuli described above affected DOPAC efflux. 5-HIAA efflux was increased (cf. basal) in the presence of an unfamiliar conspecific, but this increase was no greater than that in handled rats. It is concluded that different naturalistic stimuli cause incremental changes in the levels of extracellular NA in the frontal cortex; these changes affect both phasic and tonic components of the response.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present experiments compared the noradrenaline and behavioural responses of inbred Maudsley reactive (MR) and non-reactive (MNRA) rats when they are exposed to the light or dark arena of a light/dark shuttle-box. Behavioural scores confirmed that both strains of rats perceived the light arena to be more aversive than the dark one. Using in vivo microdialysis, exposure to the light, but not the dark, arena was found to increase noradrenaline efflux in both the frontal cortex and the hypothalamus of MNRA and MR rats. However, whereas the increase in the frontal cortex of both strains and the hypothalamus of MR rats was transient, the hypothalamic response in MNRA rats was maintained throughout exposure to the test zone. Strain differences in activity/visit and time/visit were evident but it was not possible to discern whether this could be attributed to the strain difference in the hypothalamic noradrenaline response. Nevertheless, it remains possible that, by comparison with MR rats, the prolonged noradrenaline response in the hypothalamus of MNRA rats could contribute to their well-documented, greater resistance to aversive environmental stimuli.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 98 (1989), S. 412-416 
    ISSN: 1432-2072
    Keywords: Adrenoceptors ; Behaviour ; Noradrenaline ; Open field ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were injected IP once daily for 14 consecutive days with propranolol (5 mg/kg), yohimbine (2.5 mg/kg) or saline vehicle. A fourth group was unhandled during this time. Each rat was then placed in an open field for 4 min and its activity and defaecation recorded. Immediately after this, the animals were killed and cerebral cortices removed for radioligand binding to α2- and β-adrenoceptors and measurement of noradrenaline content. We report two sets of findings. First, β-adrenoceptor density correlated positively, and affinity negatively, with the number of movements towards the centre of the field in the final 3 min of the trial. α2-Adrenoceptor K d, in contrast, correlated both with movements around the field and those directed towards the centre. Secondly, whereas the only specific drug effect was an increase in defaecation after treatment with propranolol, β-adrenoceptor density was increased and affinity decreased in all injected groups, suggesting a non-specific effect of the stress of injection. Movements to and from the centre of the field were also increased in injected groups during the first minute of the trial. In both sets of findings the association of β-adrenoceptor density with greater resistance to stress is hard to reconcile with existing theories of the role of β-adrenoceptors in behavioural responses to stress.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: Head-twitch ; 5-HT2A receptors ; 5-HT synthesis ; Stress ; Swim test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present experiments investigated the effects of a novel stress challenge (6-min swim test) on behaviour (immobility) and the neurochemistry of cortical 5-hydroxytryptaminergic neurones in CD1 mice. The influence of previous experience of stress (once-daily saline injection) or administration of the noradrenaline and 5-hydroxytryptamine (5-HT) uptake blocker, sibutramine hydrochloride, on any changes was also evaluated. 5-HT2A receptor binding was unchanged 24 h after the last injection of either saline or sibutramine alone but immobility in the swim test was reduced to the same extent by these pretreatments. Seven days, but not 3 h, after the swim test, the density of 5- HT2A receptors and the frequency of 5-HT2A receptor-mediated head-twitches were increased significantly. These increases were prevented by saline injection, but sibutramine prevented the increase in head-twitches only. Sibutramine, but not saline, reduced 5-HT synthesis and 5-HT2A receptor-mediated head-twitches 3 h after the swim and increased synthesis at 7 days. The results indicate that a brief stress can have long-term effects on central 5-hydroxytryptaminergic neurones. Previous experience of stress or sibutramine has marked, but dissimilar, effects on these changes. These findings might be relevant to long-lasting CNS disorders provoked, or aggravated, by stress.
    Type of Medium: Electronic Resource
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