Thierno Madjou Bah

Behavioural signs of depression and apoptosis in the limbic system following myocardial infarction: effects of sertraline

Abstract Depression is diagnosed in 15–30% of patients following myocardial infarction (MI) and this may also be observed in the rat. We measured the effects of the antidepressant sertraline on behavioural and biochemical events following MI in a rat model. Following surgery, MI rats and sham controls were treated with sertraline (10 mg/kg, i.p.) or saline. Subgroups of rats were tested for behavioural depression 14 days after surgery. Apoptosis was estimated in other rats by measuring caspase-3 activity and TUNEL positive cells (3 days after surgery) in limbic structures (amygdale, hippocampus, hypothalamus, frontal and prefrontal cortices). Bax/Bcl-2 ratio was measured 14 days after surgery. Behavioural signs of depression (decreased sucrose intake and forced swimming time) were found in saline-treated MI rats but not in sertraline-treated rats. Compared with controls, caspase-3 activity and TUNEL positive cells were significantly increased in most limbic structures of MI rats. High prefrontal Bax/Bcl-2 ratio in MI rats correlated with low forced swimming time. Apoptosis was not found in sertraline-treated MI rats. These results establish the bases of a rat model of depression following MI and show for the first time that a selective serotonin reuptake inhibitor prevents both behavioural and biochemical markers in this model.

Lactobacillus helveticus and Bifidobacterium longum taken in combination reduce the apoptosis propensity in the limbic system after myocardial infarction in a rat model

Myocardial infarction (MI) stimulates the release of pro-inflammatory substances that induce apoptosis in the limbic system. Pro-inflammatory cytokines are considered as the root cause of apoptosis, although the mechanism is not fully explained and/or understood at this time. In addition, depression may induce gastrointestinal perturbations that maintain the elevated levels of pro-inflammatory cytokines. It has been shown that some specific probiotic formulations may reduce gastrointestinal problems induced by stress and the pro/anti-inflammatory cytokine ratio. Therefore, we hypothesised that probiotics, when given prophylactically, may diminish the apoptosis propensity in the limbic system following a MI. Male adult Sprague-Dawley rats were given probiotics (Lactobacillus helveticus and Bifidobacterium longum in combination) or placebo in their drinking-water for four consecutive weeks. A MI was then induced in the rats by occluding the left anterior coronary artery for 40 min. Rats were killed following a 72 h reperfusion period. Infarct size was not different in the two groups. Bax/Bcl-2 (pro-apoptotic/anti-apoptotic) ratio and caspase-3 (pro-apoptotic) activity were reduced in the amygdala (lateral and medial), as well as in the dentate gyrus in the probiotics group when compared with the placebo. Akt activity (anti-apoptotic) was increased in these same three regions. No significant difference was observed in Ca1 and Ca3 for the different markers measured. In conclusion, the probiotics L. helveticus and B. longum, given in combination as preventive therapy, reduced the predisposition of apoptosis found in different cerebral regions following a MI.

Escitalopram reduces circulating pro-inflammatory cytokines and improves depressive behavior without affecting sleep in a rat model of post-cardiac infarct depression

Myocardial infarction (MI) in rats is followed by a behavioral syndrome similar to human post-MI depression. We tested the effects of escitalopram, a selective serotonin reuptake inhibitor, on this syndrome. MI was induced in 19 Sprague-Dawley rats by occluding the left anterior descending coronary artery for 40min, followed by reperfusion. A sham-operated group of 20 rats was submitted to the same protocol without coronary artery occlusion. Fifteen minutes after the onset of reperfusion, escitalopram (10mg/kg/day, i.p.) or saline was infused continuously through osmotic minipumps. After 2weeks of treatment, the rats were tested for behavioral despair and anhedonia by the forced swimming and sucrose preference tests, respectively. They were then sacrificed, and blood levels of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), PGE(2) and corticosterone were measured. In a separate cohort of 24 rats, sleep was recorded after 2weeks of post-MI treatment with escitalopram or saline. In MI rats, behavioral despair and anhedonia were blocked by escitalopram but prolonged sleep latency, low total sleep time and short latency to paradoxical sleep (PS) were not; escitalopram decreased PS in sham controls. Plasma TNF-α, PGE(2), and corticosterone levels were higher in MI rats than in the controls. Escitalopram lowered TNF-α, IL-1β, and PGE(2) levels in both groups of rats while IL-6 showed no differences whatsoever. Escitalopram reverses post-MI behavioral syndrome in rats through a mechanism that could involve a reduction of pro-inflammatory cytokines and PGE(2). It has limited effects on sleep disorders in MI rats but reduces PS in control rats.

Effects of different dietary omega-6/3 polyunsaturated fatty acids ratios on infarct size and the limbic system after myocardial infarction

Changes in dietary omega-6/3 polyunsaturated fatty acids (PUFA) ratios affect anti- and proinflammatory equilibrium. As reperfused myocardial infarction (MI) is an inflammatory pathology that alters the cell integrity of the myocardium but also of other tissues, such as the hippocampus and amygdala, attenuation of the inflammation could be helpful in maintaining cell integrity after MI. Therefore, we hypothesized that a decrease in the dietary omega-6/3 PUFA ratio, without altering the diet content in total fat, proteins, or carbohydrates, will result in a reduction of infarct size and a diminution of postreperfusion apoptosis observed in the amygdala and hippocampus. Male Sprague-Dawley rats were fed 1 of 3 diets containing different omega-6/3 PUFA ratios for 2 weeks (5:1; 1:1; 1:5). Then, myocardial ischemia was induced by left anterior descending coronary artery occlusion for 40 min, followed by reperfusion. Cardioprotective mechanisms were studied in the myocardium at 15 min of reperfusion, along with myocardial infarct size after 24 h of reperfusion. Apoptosis was evaluated in the hippocampus and the amygdala. We found that infarct size was significantly reduced by 32% in groups 1:5 and 1:1 vs. group 5:1. Akt activity was higher in groups 1:5 and 1:1 compared with group 5:1. Caspase-3 enzymatic activity doubled in area CA1 and the dentate gyrus (DG) in group 5:1 compared with groups 1:1 and 1:5. In addition, caspase-8 enzymatic activity was increased in the DG at 24 h, and caspase-9 was enhanced in CA1 at 24 h in group 5:1 vs. groups 1:1 and 1:5. These results demonstrate that the increase in the dietary omega-3 PUFA, at the expense of omega-6 PUFA, reduces infarct size and helps to inhibit apoptosis in the limbic system after MI.

Pretreatment with pentoxifylline has antidepressant-like effects in a rat model of acute myocardial infarction.

We have observed that, after myocardial infarction (MI), rats display apoptosis in the limbic system that can be prevented by pentoxifylline (PTX), a proinflammatory cytokine inhibitor. We have hypothesized that reduction of apoptosis in the limbic system can attenuate the depressive behaviour occurring post-MI. The present study was, therefore, designed to assess the outcome of PTX on depressive behaviour manifesting after MI. Myocardial ischaemia, induced for 40 min in male Sprague–Dawley rats, was followed by reperfusion (MI groups). Sham groups were subjected to the same protocol without occlusion. PTX (10 mg/kg/day) or saline was administered intraperitoneally 15 min before ischaemia, and then every day until sacrifice. Two weeks after ischaemia, depression was evaluated by the forced swim test and the sucrose preference test. At the end of the experiment, the animals were sacrificed, and myocardial infarct size was examined along with plasma IL-1&bgr; concentrations. MI rats drank less sucrose in the sucrose preference test and were more immobile in the forced swim test than the sham controls. PTX reversed these behaviours in the MI group to a level similar to that in the untreated sham group, without affecting infarct size. PTX reduced plasma IL-1&bgr; concentrations in both sham and MI rats. We conclude that PTX administration significantly reverses the depressive-like behaviour seen after MI in rats.

Chronic pretreatment with celecoxib reduces infarct size.

This study was designed to evaluate the effect of long-term pretreatment with celecoxib, a cyclooxygenase-2 inhibitor, on myocardial infarct size. Celecoxib (3 mg/kg/day i.p; n = 16) or vehicle (DMSO 50%; EtOH 15%; distilled water, n = 16) was administered chronically to male Sprague-Dawley rats through ALZET osmotic pumps for 28 days. Under anaesthesia, the animals were then subjected to left anterior descending coronary artery occlusion for 40 minutes, followed by 24-hour reperfusion. The results show that myocardial infarct size in celecoxib-treated rats was significantly reduced compared to the control group (37.5 ± 2.5% versus 48.0 ± 2.6% of the area at risk, P < 0.05, n = 10 per group). Accumulation of neutrophils, estimated by myeloperoxidase levels, indicated an increase in the ischemic area without any significant difference between groups. No significant difference was observed between the treated and vehicle groups in terms of plasma prostaglandin E2 and tumour necrosis factor-alpha. Apoptosis, evaluated by Bax/Bcl-2 and terminal dUTP nick-end labelled-positive cells, was significantly decreased in the subendocardial layer of the ischemic area in celecoxib-treated rats. This study indicates that pretreatment with celecoxib can reduce infarct size by a mechanism, which may involve apoptosis inhibition.

Effect of olfactory bulbectomy on adenylyl cyclase activity in the limbic system

Monoaminergic neurotransmission is a key element in the physiopathology of depressive disorders, but information is still sparse on animal models of this disease. Here, we used the olfactory bulbectomy (OBX) model of depression to characterize cAMP-second messenger signaling pathways, i.e., adenylyl cyclase activity (basal, sodium fluoride (NaF)- and forskolin-stimulated conditions) as well as Gi and Gs protein levels in different regions of the limbic system. Two weeks after surgery and compared to sham controls, OBX rats displayed reduced NaF-stimulated adenylyl cyclase activity and increased Gi/Gs ratios in the hypothalamus, pre-frontal and cingulate cortices but not in the amygdala, hippocampus and caudate nucleus. No differences were found in basal or forskolin-stimulated conditions. The observed reduction of adenylyl cyclase activity induced by NaF and the increase in the Gi/Gs ratio could explain the changes in neurotransmission in OBX rats as well as in humans with depression.

T-O-121 ESCITALOPRAM REDUCES INFLAMMATION AND IMPROVES BEHAVIOR WITHOUT AFFECTING SLEEP IN A RAT MODEL OF POST CARDIAC INFARCT DEPRESSION

awakenings in every spectral frequency studied, in relation to the group and presence or absence of recall. The various spectral bands evolved according to an underlying rhythm, which is attenuated in the presence of dream recall; this was more evident in Normal subjects. Verbal activities were negatively correlated with high frequency bands in C3, T5 and P3 electrodes in controls. Conclusion: Differences between recall and no recall were detected. The spectral frequency bands powers were attenuated with dream recall. A cyclic variation in spectral power was detected in association with recall. Verbal activities correlated with high frequencies in left centro-temporoparietal areas.