E. Toth

Age-dependent effects of chronic stress on brain plasticity and depressive behavior

Exposure to chronic mild stress (CMS) is known to induce anhedonia in adult animals, and is associated with induction of depression in humans. However, the behavioral effects of CMS in young animals have not yet been characterized, and little is known about the long‐term neurochemical effects of CMS in either young or adult animals. Here, we found that CMS induces anhedonia in adult but not in young animals, as measured by a set of behavioral paradigms. Furthermore, while CMS decreased neurogenesis and levels of brain‐derived neurotrophic factor (BDNF) in the hippocampus of adult animals, it increased these parameters in young animals. We also found that CMS altered α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptor GluR1 subunit levels in the hippocampus and the nucleus accumbens of adult, but not young animals. Finally, no significant differences were observed between the effects of CMS on circadian corticosterone levels in the different age groups. The substantially different neurochemical effects chronic stress exerts in young and adult animals may explain the behavioral resilience to such stress young animals possess.

Site-Specific Antidepressant Effects of Repeated Subconvulsive Electrical Stimulation: Potential Role of Brain-Derived Neurotrophic Factor

BACKGROUNDnElectroconvulsive therapy (ECT) is a very effective treatment for major depression. This method involves robust nonfocal stimulation of the brain and can normalize both neurochemical alterations and depressive behavior in animal models. We hypothesized that short stimulation sessions of specific reward-related brain sites might induce similar effects.nnnMETHODSnIn the present study we compared behavioral and neurochemical effects produced by ECT and by repeated stimulation of reward-related brain sites, in a widely used rat model for depressive behavior induced by chronic mild stress (CMS). Different groups of rats received 10 sessions of either electroconvulsive shocks or subconvulsive electrical stimulation (SCES) of specific brain sites with an implanted electrode. The SCES temporal parameters were similar to those used in transcranial magnetic stimulation studies in humans. A battery of behavioral tests and measurements of brain-derived neurotrophic factor (BDNF) levels were used to assess the effectiveness of these treatments relative to sham treatments.nnnRESULTSnRepeated SCES of either the nucleus accumbens (NAC) or the ventral but not the dorsal prelimbic cortex (PLC) reversed the main behavioral deficit and the reduction of BDNF levels in the hippocampus that were induced by CMS. The ECT was more effective because it also normalized a behavioral deficit associated with anxiety but produced a learning and memory impairment.nnnCONCLUSIONSnThis study implicates the ventral PLC and the NAC in the pathophysiology of depressive behavior and suggests that local intermittent SCES can induce an antidepressant effect similar to that of ECT, without the cognitive impairment caused by the convulsive treatment.

Neonatal and juvenile stress induces changes in adult social behavior without affecting cognitive function

The aim of the present study was to test the hypothesis that exposure to neonatal and/or juvenile stress results in distinct persisting modification of adult male rats emotional and social competence. Compared to non-stressed control rats, neonatally stressed rats and rats exposed to combined neonatal and juvenile stress, had reduced frequency and duration of social encounters, and lower anxiety levels. Juvenile stress alone, induced more frequent, but shorter social encounters in adulthood. No significant differences in aggressive behavior were found between any of the groups. The findings confirm the existence of developmental time windows during which exposure to unpredictable stress can affect adult emotional and social behavior without affecting cognitive function.

Unpredictable chronic stress in juvenile or adult rats has opposite effects, respectively, promoting and impairing resilience

We evaluated the effects of early maternal deprivation (MD; age 7–14 days) alone or in combination with unpredictable chronic stress (UCS; MDUN; 28–84 days) on anxiety and learning in 90 days old adult rats. We hypothesized that exposure to both stressors (MDUN) would be more detrimental than exposure to one or neither. Unexpectedly, adult rats from the MDUN group did not differ from control animals, whereas adult MD animals exhibited impaired avoidance learning. We next investigated the effect of juvenile-onset (30–90 days) versus adult-onset (60–90 days) stress on avoidance learning in adulthood (90 days). We found that adult-onset chronic stress impaired avoidance learning and memory whereas juvenile-onset stress did not. Thus, the results again indicate that juvenile exposure to UCS induces resilience rather than impairment.

P022 Subconvulsive electrical stimulation of the nucleus accumbens increases sexual drive and hippocampal brain-derived neurotrophic factor (BDNF) after chronic mild stress

threshold of stimulation in the course of adaptation of her organism to future labour, which is accompanied by protection against influence of strong stimuli. Purpose: Interpretation of headache intensity in pregnant women with preeclampsia. Methods: We assessed intensity of headache (using CPS scale) in 40 pregnant women with preeclampsia. 13 women were diagnosed with “mild preeclampsia”, 15 with “moderate preeclampsia”, and 12 with “severe preeclampsia”. CPS scale gives the following degrees of pain: absence of pain, mild pain, moderate pain, strong pain, and maximal pain. The headache was localized predominantly in frontotemporal and occipital zones (mediated through the system of n.trigeminus and branches of n.glossopharyngeus and n.vagus). Results: We obtained the following headache characteristics: in mild preeclampsia 7 women – absence of pain, 4 women – mild pain, 2 women – moderate pain. In moderate preeclampsia: 4 women – absence of pain, 5 women – mild pain, 6 women – moderate pain. In severe preeclampsia: 2 women – moderate pain, 7 women – strong pain, 3 women – maximal pain. In all cases the headache did not coincide in time with increase of blood arterial pressure. Conclusions: This data reveal the increase in pain barrier along with sensory adaptation to it in pregnant women with mild to moderate preeclampsia. In case of severe preeclampsia takes place decrease in pain barrier along with sensory desadaptation to pain, which reflects overstrain of the body and depletion of mechanisms of adaptation and protection. This should be considered during clinical diagnosing of preeclampsia severity and, particularly, of headache severity in pregnant women.