Effects of two stressors on behaviour in the elevated X-maze: preliminary investigation of their interaction with 8-OH-DPAT.
Effects of water deprivation and restraint were compared in the rat elevated X-maze. Water deprivation for 12-48 h increased corticosterone and had a duration-dependent "anxiolytic" effect in the elevated X-maze, increasing the ratio of open/total arm entries (OTR) and the proportion of time spent on the open arms (% time) without affecting total entries. Brain 5HIAA/5HT was increased only after 24 or 48 h deprivation. Restraint for 15 min also increased plasma corticosterone and brain 5HIAA/5HT but had no effect on behaviour in the elevated X-maze when rats were tested immediately afterwards. However, 1 h restraint was "anxiogenic" in the elevated X-maze immediately after release, reducing OTR and % time, but with a less consistent reduction in total entries; reductions in OTR and % time were still present 24 h later. The 5HT1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) (0.1-0.2 mg/kg), administered 10 min before testing in the elevated X-maze, had "anxiogenic" actions in non-stressed rats. The effect of 0.1 mg/kg 8-OH-DPAT was not significantly altered by 24 or 48 h water deprivation but was abolished by restraint for 1 h immediately beforehand, despite the "anxiogenic" effect of restraint alone. Similar mutual antagonism of 8-OH-DPAT and restraint occurred when the dose of 8-OH-DPAT was increased to 0.2 mg/kg. Twenty-four hours after restraint, restrained rats which had received 8-OH-DPAT (0.1-0.2 mg/kg) still did not show any significant "anxiogenic effect" compared with non-restrained vehicle treated controls. Restraint-induced deficits in elevated X-maze exploration may prove a useful model with which to study the pharmacology of depression-related anxiety. However, the effects of the stressors examined, and their interaction with 8-OH-DPAT in the elevated X-maze, appear to depend on the nature of the stressor.
McBlane
J W
JW
Pharmaceutical Sciences Institute, Aston University, Birmingham, UK.
Handley
S L
SL
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D001007:Anxiety / Q000378:metabolism / Q000523:psychology*; D001522:Behavior, Animal / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D005106:Exploratory Behavior / Q000187:drug effects; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D012701:Serotonin / Q000378:metabolism; D013315:Stress, Psychological / Q000378:metabolism / Q000523:psychology*; D014868:Water Deprivation / Q000502:physiology*
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D003345:Corticosterone