Effects of neonatal alcohol and/or cocaine exposure on stress in juvenile and adult female rats

The participation of a neurocircuit from the paraventricular thalamus to amygdala in the depressive like behavior

Depression is a neuropsychological disease derived from genetic, biochemical, environmental, and psychological factors. However the neurocircuits involved in it are not clear. We introduced the forced swimming test (FST) as a model of the depressive like behavior. In our study, the participation of projections from paraventricular nucleus of the thalamus (PVT) in FST was detected. The retrograde tracing combined with immunofluorescent detection of c-fos was used. Our results showed that the FST greatly increased the c-fos level in PVT and the central amygdale (CE) neurons. These populations of activated neurons in the PVT and the CE were also labeled by the retrograde tracer FG injected in the CE, suggesting that the activation of PVT was involved in this depressive like behavior by relaying information to the CE.

Chronic treatment with 13-cis-retinoic acid changes aggressive behaviours in the resident-intruder paradigm in rats

Retinoids, vitamin A related compounds, have an established role in the development of the nervous system and are increasingly recognized to play a role in adult brain function. The synthetic retinoid, 13-cis-retinoic acid (13-cis-RA, Roaccutane) is widely used to treat severe acne but has been linked to an increased risk of neuropsychiatric side effects, including depression. Here we report that chronic administration with 13-cis-RA (1 mg/kg i.p. daily, 7-14 days) in adult rats reduced aggression- and increased flight-related behaviours in the resident-intruder paradigm. However, in the forced swim, sucrose consumption and open field tests treatment for up to 6 weeks with 13-cis-RA did not modify behaviour in adult or juvenile animals. The behavioural change observed in the resident-intruder paradigm is directly opposite to that observed with chronic antidepressant administration. These findings indicate that when a suitably sensitive behavioural test is employed then chronic administration of 13-cis-RA in adult rats induces behavioural changes consistent with a pro-depressant action.

Hormonal, neurochemical, and behavioral response to a forced swim test in adolescent rats throughout cocaine withdrawal

The use of cocaine in adults has been linked to depression and/or anxiety. Several studies have shown an association between cocaine-primed craving and depressive symptoms. In animal models, the forced swim test (FST) is frequently used for screening depressive-like behavior. This study aimed to verify the presence of depression-like symptoms in adolescent rats after chronic cocaine exposure by analyzing behavior in a FST. The subsequent alterations in neurotransmitters and hypothalamus-pituitary-adrenal axis activity induced by this test were also analyzed. Both male and female adolescent Wistar rats were submitted to a chronic "binge" pattern of administration of cocaine hydrochloride, and subjects were tested in a forced swim test 2 days after cocaine's last administration. At the end of the behavioral test, trunk blood was collected for quantification of corticosterone plasma levels, and hypothalamus, prefrontal cortex, amygdala, and hippocampus were dissected for neurochemical determinations. No significant differences were found in the behavior on the FST of both males and females after withdrawal from chronic cocaine administration. Nevertheless, plasma levels of corticosterone were increased in cocaine-treated males, although not significantly (P= 0.065). In females cocaine failed to affect corticosterone levels. Of interest, neurochemical analyses showed that dopamine turnover was decreased in amygdala in cocaine-treated males (not significantly, P= 0.055). No significant differences were found on neurotransmitter levels in the other brain regions analyzed. Withdrawal from chronic cocaine administration during adolescence did not have a significant effect on stress-induced behavioral alterations, although the neurochemical response to the stressful situation provided by FTS seemed to be affected.

Exploratory behavior in rats postnatally exposed to cocaine and housed in an enriched environment

Exposure to cocaine in early periods of postnatal life is usually associated with changes in development of neurotransmitter systems and structure of the central nervous system. Such changes are most likely correlated with behavioral alterations. Environmental enrichment conditions (EC) in early stages is a factor that affects structural and behavioral development. The purpose of this study is to examine the effects of EC on rats postnatally exposed to cocaine on exploratory behavior. Wistar rats were assigned to four groups-Group 1: pups exposed to cocaine hydrochloride (15 mg/kg body weight/day) s.c., in two daily doses, from postnatal day (PND) 1 to 28 and reared in EC; Group 2: pups exposed to cocaine as previously described and reared in a standard environmental conditions (SC); Group 3: pups saline-injected and reared in EC; and Group 4: pups saline-injected and reared in SC. On PND 21, 24, and 28, groups of four rats (to reduce anxiety) were placed for 10 minutes into an arena with several objects. The following exploratory behavioral categories were examined: object interaction, exploration, manipulation, approximation, and total time of object contact. Animals from Group 2 showed decreased object interaction and total contact on PND 21. Control offspring reared in EE showed decreases in exploratory behavior at all ages analyzed compared with the control SE group, while cocaine-exposed animals reared in EC showed decreased object interaction, object approximation, and total exploratory behavior. The results in this group suggest that EC improved information acquisition and memory processes in animals postnatally exposed to cocaine.

Chronic Oral Treatment with 13-cis-Retinoic Acid (Isotretinoin) or all-trans-Retinoic Acid Does Not Alter Depression-Like Behaviors in Rats

Oral treatment with the anti-acne drug Accutane (isotretinoin, 13-cis-retinoic acid) has been associated with suicide ideation and depression. Here, depression-like behaviors (i.e., behavioral despair and anhedonia) were quantified in adult Sprague-Dawley rats gavaged daily beginning at postnatal day (PND) 82 with 13-cis-RA (7.5 or 22.5 mg/kg) or all-trans-retinoic acid (10 or 15 mg/kg ). Tested at PND 130-131 in the Forced Swim Test, 7.5 mg/kg 13-cis-RA marginally decreased immobility and slightly increased climb/struggle durations whereas neither all-trans-retinoic acid group differed from controls. Voluntary saccharin solution (0.03%) intake at PND 102-104 and PND 151-153 was not different from controls in any treated group, although all RA-treated groups had lower intakes. Swim speed in a water maze at PND 180 was similar across groups, indicating no RA-induced differences in physical ability. Open field activity was mildly decreased at PND 91 in 7.5 mg/kg-treated males only, but it was within the control range at PND 119, 147, and 175. Thus, at serum levels similar to those in humans receiving the drug, chronic 13-cis-RA treatment did not severely affect depression-like behaviors in rats. These data do not substantiate the hypothesis of 13-cis-RA-induced depression.