Plasma catecholamine and corticosterone levels during active and passive shock-prod avoidance behavior in rats: Effects of chlordiazepoxide

Abstract

Plasma noradrenaline (NA), adrenaline (A) and corticosterone (CS) concentrations were determined in rats before, during and after 15-min exposure to a constantly electrified (2 mA) or nonelectrified prod which was mounted on the wall of the home cage either with or without bedding material on the floor. Concomitantly, exploration of the prod, freezing and prod-burying behavior were recorded. Both in the presence and absence of bedding material, rats explored the nonelectrified prod and showed a small increase in plasma NA and CS contents. Exploration of the prod was strongly reduced when the prod was electrified. In the presence of bedding material, shocked rats typically displayed burying behavior (active avoidance), whereas in the absence of bedding (i.e., burying option eliminated) shocked rats engaged in freezing behavior (passive avoidance). The passive avoidance situation was accompanied by larger A and CS increases but a lower NA rise as compared to the hormonal responses associated with the active avoidance situation. Administration of the anxiolytic chlordiazepoxide (CDP; 9 mg/kg intragastrically) attenuated the shock-induced suppression of prod exploration, decreased prod-burying behavior but, paradoxically, increased freezing behavior. Irrespective of bedding condition, the prod shock-induced elevations in plasma CS and A contents were completely abolished in CDP-treated rats. The rise in plasma NA was attenuated only in CDP-treated rats tested on a bedding-floor. The results indicate that passive (e.g., freezing) and active (e.g., burying) behavioral coping are each accompanied by specific and dissociated patterns of neurosympathetic, adrenomedullary and adrenocortical outflow. CDP-treatment shifts an animal's behavioral coping style from an active to a passive form of avoidance responding, but abolishes the accompanying adrenocortical and adrenomedullary activation.

Conditioned neuroendocrine and cardiovascular stress responsiveness accompanying behavioral passivity and activity in aged and in young rats

“…The test was performed in each individual's home cage in order to avoid disturbance of the neuroendocrine and cardiovascular system by intercage transfer (10,22). A removable teflon probe (6.5 cm long, 1 cm in diameter) was inserted 2 cm above the bedding material (wood shavings) through a small hole in the center of the front wall of the Plexiglas cage.…”

“…They were then centrifuged at 4°C for 10 rain at 5000 rpm, and 100 ul of the supernatant were stored at -20°C for CORT and at 80°C for the catecholamine (CA) measurements. Plasma CORT was measured by means of reversed phase high performance liquid chromatography (HPLC), as described earlier (10). Determination of plasma CA concentrations was performed by HPLC in combination with electrochemical detection (23,38).…”

Differential blockade of CRF-evoked behaviors by depletion of norepinephrine and serotonin in rats

“…Rodent burying behavior has long been described as a defensive coping strategy in natural habitats (Calhoun 1962;MacClintock 1970;Owings and Coss 1977). Furthermore, in the context of defensive avoidance, this proactive form of stress management provides an index of anxiety when directed at an electrified probe (Bondi et al 2007;De Boer et al 1990;Korte et al 1992;Treit et al 1981), and is enhanced and attenuated by anxiogenic and anxiolytic drugs, respectively (De Boer and Koolhaas 2003;Diamant et al 1992). To the best of our knowledge, the present studies are the first to specifically characterize and quantify the burying response to i.c.v.…”

Fluoxetine Disrupts the Integration of Anxiety and Aversive Memories

“…In this test, rats shocked from a stationary, electrified probe push bedding material from the floor of the experimental chamber toward the shock-probe (ie they bury the probe), avoid further contacts with the probe, and exhibit freezing behavior (Treit et al, 1994(Treit et al, , 1981Frye and Seliga, 2003;Pinel and Treit, 1978). In rats it has been demonstrated that anxiolytic drugs such as diazepam decrease burying towards the shock-probe (de Boer et al, 1990;Treit et al, 1993;Tsuda et al, 1988), whereas anxiogenic drugs such as yohimbine increase shock-probe burying (Tsuda et al, 1988). During the training session, burying behavior and the total number of contact-induced shocks each rat received were measured.…”