Repeated stress increases locomotor response to amphetamine

Abstract

Adult male rats submitted to mild, 20 min electric foot shock sessions for 10 days displayed an enhanced locomotor response to 0.75 mg/kg (+)amphetamine 24 h after the last shock session, when compared to non-stressed controls. This effect was still present in rats specifically deprived of their forebrain noradrenergic innervation, suggesting the involvement of a dopaminergic mechanism. Cortical and limbic dopamine turnover which increased immediately after acute and repeated foot shocks returned to normal 24 h later, at the time of the pharmacological testing. This fact indicates that a permanent modification of the basal DA activity is not responsible for the above effect of stress. Locomotor hyperactivity produced by 0.6 mg/kg apomorphine was enhanced in experimental animals, while hypoactivity resulting from the injection of 0.05 mg/kg apomorphine was similar in control and shocked rats. This latter result suggests the existence of an increased postsynaptic DA sensitivity as a result of repeated stress.

Emerging Evidence for a Central Epinephrine-Innervated α1-Adrenergic System that Regulates Behavioral Activation and is Impaired in Depression

“…In agreement, a number of studies have shown that there is a reduced level of DA and its metabolites in the CSF of depressed patients (Brown and Gershon, 1993) and also a reduced release and metabolism of DA in the basal ganglia of animals subjected to stressors that induce behavioral depression (Cabib and Puglisi-Allegra, 1996). This reduction, however, does not appear to be caused by a direct impairment of the dopaminergic neurons or postsynaptic receptors themselves (Weiss et al, 1996;Cabib et al, 1998;Ossowska et al, 2001;Herman et al, 1984;ZebrowskaLupina et al, 1988), but may occur instead in an afferent system that modulates dopaminergic function. One such afferent system that is particularly sensitive to stress and has been implicated in depressive illness is the a 1 -adrenergic (Lipinski et al, 1987;.…”

Dysthymia: a review of pharmacological and behavioral factors

“…[94][95][96] Since humans typically encounter chronic, intermittent and unpredictable stressors, it may be more relevant to assess the effects of such regimens in animal studies. In contrast to the amine reductions induced by acute stressors, transmitter levels equal or exceed control values following protracted or repeated stressors, 93,[97][98][99][100] owing to increased amine synthesis and/or moderation of excessive utilization. 98,101 Moreover, chronic insults affect the amine variations engendered by later stressors.…”

“…In contrast to the amine reductions induced by acute stressors, transmitter levels equal or exceed control values following protracted or repeated stressors, 93,[97][98][99][100] owing to increased amine synthesis and/or moderation of excessive utilization. 98,101 Moreover, chronic insults affect the amine variations engendered by later stressors. Specifically, in addition to a sensitization with respect to amine utilization (as seen following acute stressors), chronic stressors also induce sensitization of amine synthesis, thereby assuring adequate transmitter levels upon later stressor encounters.…”

Heightened Cocaine and Food Self-Administration in Female Rats with Neonatal Isolation Experience

“…Although a majority of cocaine addicts are male, female addicts are more likely than males to have comorbid post-traumatic stress disorder (Najavits et al, 1998) or a history of child abuse (Wechsberg et al, 1998). In rats, stress increases the ability of psychoactive drugs to enhance locomotor activity (Herman et al, 1984;Leyton and Stewart, 1990;Deroche et al, 1995;Haile et al, 2001), support place conditioning (Bell et al, 1997;Will et al, 1998;Haile et al, 2001), and promote acquisition of self-administration behavior (Piazza et al, 1990;Deminiere et al, 1992;Haney et al, 1995;Tidey and Miczek, 1997;Kosten et al, 2000). A few studies have examined the effects of stress on drug self-administration after behavior is well established (ie maintenance conditions), and report enhanced responding after stress (Shaham and Stewart, 1994;Zhang et al, 2005).…”