scholarly journals Infection of male rats with Toxoplasma gondii results in enhanced delay aversion and neural changes in the nucleus accumbens core

2015 ◽  
Vol 282 (1808) ◽  
pp. 20150042 ◽  
Author(s):  
Donna Tan ◽  
Linda Jing Ting Soh ◽  
Lee Wei Lim ◽  
Tan Chia Wei Daniel ◽  
Xiaodong Zhang ◽  
...  
Keyword(s):  
Nucleus Accumbens ◽  
Toxoplasma Gondii ◽  
Intertemporal Choice ◽  
Behavioural Change ◽  
Male Rats ◽  
Spine Density ◽  
Delay Aversion ◽  
Nucleus Accumbens Shell ◽  
Nucleus Accumbens Core ◽  
Accumbens Core

Rats infected with the protozoan parasite Toxoplasma gondii exhibit reduced avoidance of predator odours. This behavioural change is likely to increase transmission of the parasite from rats to cats. Here, we show that infection with T. gondii increases the propensity of the infected rats to make more impulsive choices, manifested as delay aversion in an intertemporal choice task. Concomitantly, T. gondii infection causes reduction in dopamine content and neuronal spine density of the nucleus accumbens core, but not of the nucleus accumbens shell. These results are consistent with a role of the nucleus accumbens dopaminergic system in mediation of choice impulsivity and goal-directed behaviours. Our observations suggest that T. gondii infection in rats causes a syndromic shift in related behavioural constructs of innate aversion and making foraging decisions.

scholarly journals Sex-Dependent Ketamine Addiction-Like Behavior Profile Following Exposure to Chronic Mild Stress

2019 ◽  
Vol 3 ◽  
pp. 247054701983261 ◽  
Author(s):  
Katherine N. Wright ◽  
Devin P. Hagarty ◽  
Caroline E. Strong ◽  
Kristin J. Schoepfer ◽  
Mohamed Kabbaj
Keyword(s):  
Nucleus Accumbens ◽  
Chronic Mild Stress ◽  
Abuse Potential ◽  
Prior Exposure ◽  
Female Rats ◽  
Male Rats ◽  
Mild Stress ◽  
Spine Density ◽  
Nucleus Accumbens Core ◽  
Accumbens Core

Background Ketamine has rapid antidepressant effects and shows great promise as a novel treatment for depression, but its limitations including its abuse potential are poorly understood. Given that the prevalence of depression is twice as high in women as in men and that depression and substance use disorders are highly comorbid, we hypothesized that a sex-specific responsivity to behavioral assays that characterize addiction-like behavior may arise in rats with prior exposure to chronic stress and therapeutically relevant ketamine. Methods Male and female rats that underwent chronic mild stress were treated with four 1.47 mg/kg intravenous ketamine infusions once every fourth day and underwent operant self-administration of 0.5 mg/kg/infusion ketamine. Measures of anhedonia (or lack of pleasure, a signature feature of depression), anxiety-induced neophagia, motivation to obtain ketamine, and craving were assessed using the sucrose intake test, novelty-suppressed feeding test, progressive ratio schedule of reinforcement, and incubation of craving following abstinence, respectively. Finally, dendritic spine density in the nucleus accumbens core was measured. Results Ketamine infusions reduced anxiety-induced neophagia in both male rats and female rats but had no effect on measures of anhedonia. Female rats with prior exposure to chronic mild stress had greater motivation to obtain ketamine compared to nonstressed female rats, an effect not observed in male rats. Additionally, female rats who received antidepressant ketamine infusions had a higher threshold for displaying ketamine addiction-like behavior than saline-treated female rats as well as increased thin spine density in the nucleus accumbens core. These effects were not observed in male rats. Conclusion This study shows that repeated low-dose ketamine does not increase abuse potential of subsequent ketamine. It also highlights an important female-specific effect of stress to increase ketamine addiction-like behavior, which requires further investigation for clinical populations.

scholarly journals The nucleus accumbens core is necessary to scale fear to degree of threat

2020 ◽  
Author(s):  
Madelyn H. Ray ◽  
Alyssa N. Russ ◽  
Rachel A. Walker ◽  
Michael A. McDannald
Keyword(s):  
Nucleus Accumbens ◽  
Anxiety Disorders ◽  
Male Rats ◽  
Nucleus Accumbens Core ◽  
General Role ◽  
Discrimination Procedure ◽  
Neurotoxic Lesion ◽  
Long Evans ◽  
Rapid Discrimination ◽  
Accumbens Core

AbstractFear is adaptive when the level of the response rapidly scales to degree of threat. Using a discrimination procedure consisting of danger, uncertainty and safety cues, we have found rapid fear scaling (within two seconds of cue presentation) in male rats. Here we examined a possible role for the nucleus accumbens core (NAcc) in the acquisition and expression of fear scaling. In experiment 1, male Long Evans rats received bilateral sham or neurotoxic NAcc lesions, recovered and underwent fear discrimination. NAcc-lesioned rats were generally impaired in scaling fear to degree of threat, and specifically impaired in rapid uncertainty-safety discrimination. In experiment 2, male Long Evans rats received NAcc transduction with halorhodopsin or a control fluorophore. After fear scaling was established, the NAcc was illuminated during cue or control periods. NAcc-halorhodopsin rats receiving cue illumination were specifically impaired in rapid uncertainty-safety discrimination. The results reveal a general role for the NAcc in scaling fear to degree of threat, and a specific role in rapid discrimination of uncertain threat and safety.Significance StatementRapidly discriminating cues for threat and safety is essential for survival and impaired threat-safety discrimination is a hallmark of stress and anxiety disorders. In two experiments, we induced nucleus accumbens core (NAcc) dysfunction in rats receiving fear discrimination consisting of cues for danger, uncertainty and safety. Permanent NAcc dysfunction, via neurotoxic lesion, generally disrupted the ability to scale fear to degree of threat, and specifically impaired one component of scaling: rapid discrimination of uncertain threat and safety. Reversible NAcc dysfunction, via optogenetic inhibition, specifically impaired rapid discrimination of uncertain threat and safety. The results reveal that the NAcc is essential to scale fear to degree of threat, and is a plausible source of dysfunction in stress and anxiety disorders.

scholarly journals Optogenetic activation of basolateral amygdala projections to nucleus accumbens core promotes cue-induced expectation of reward but not instrumental pursuit of cues

2021 ◽  
Author(s):  
Alice Servonnet ◽  
Pierre-Paul Rompré ◽  
Anne-Noël Samaha
Keyword(s):  
Nucleus Accumbens ◽  
Basolateral Amygdala ◽  
Male Rats ◽  
Water Delivery ◽  
Nucleus Accumbens Core ◽  
Approach Behavior ◽  
Optogenetic Stimulation ◽  
Conditioned Approach ◽  
Stimulation Of ◽  
Accumbens Core

Reward-associated conditioned stimuli (CS) can acquire predictive value, evoking conditioned approach behaviors that prepare animals to engage with forthcoming rewards. Such CS can also acquire conditioned reinforcing value, becoming attractive and pursued. Through their predictive and conditioned reinforcing properties, CS can promote adaptive (e.g., locating food) but also maladaptive responses (e.g., drug use). Basolateral amygdala neurons projecting to the nucleus accumbens core (BLA→NAc core neurons) mediate the response to appetitive CS, but the extent to which this involves effects on the predictive and/or conditioned reinforcing properties of CS is unclear. Thus, we examined the effects of optogenetic stimulation of BLA→NAc core neurons on conditioned approach behavior and on the instrumental pursuit of a CS, the latter a measure of conditioned reinforcement. Water-restricted, adult male rats learned that a light-tone compound cue (CS) predicts water delivery. Pairing optogenetic stimulation of BLA→NAc core neurons with CS presentation potentiated conditioned approach behavior, and did so even under extinction conditions, when water was omitted. This suggests that BLA→NAc core neurons promote cue-induced expectation of rewards. Rats also received instrumental conditioning sessions during which they could lever press for CS presentations, without water delivery. Optogenetic stimulation of BLA→NAc core neurons either during these instrumental test sessions or during prior CS-water conditioning did not influence lever responding for the CS. This suggests that BLA→NAc core neurons do not influence the conditioned reinforcing effects of CS. We conclude that BLA→NAc core neurons promote cue-induced control over behavior by increasing cue-triggered anticipation of rewards, without influencing cue 'wanting'.

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