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BACKGROUND AND AIMS: Stress plays a crucial role in the development of neuropsychiatric disorders, such as depression and schizophrenia. In animals, chronic stress impairs several brain systems, including dopaminergic (DA) neurotransmission. DA, apart from its involvement in the brain mechanisms of reward, regulates cognitive functions that are likewise disrupted in depression and schizophrenia. The impact of chronic stress on this regulation is, however, much less recognized. METHODS: One of the many models used in preclinical studies on the interaction between stress and human diseases is a chronic mild stress (CMS) procedure. In this model animals, subjected to a variety of mild stressors for a period of several weeks, develop impairments, which show striking similarity to symptoms of human depression and schizophrenia. The purpose of this project was to study the effect of intracranial injections of agonists and antagonists of D1, D2 and D3 on behaviour of control animals and stressed animals in the Novel Object Recognition (NOR) test. RESULTS: It was found that in the control animals a significant and dose-dependent improvement of the NOR behaviour was caused by D1 agonist SKF 81297 (0.05–0.75 µg) injected into prefrontal cortex (PFX), hippocampus (HPC) and nucleus accumbens septi (NAS), D2 agonist Quinpirole (0.1–5 µg) injected into PFX and HPC, and D3 antagonist SB 277-011 (0.1–1 µg) injected into PFX and HPC. The enhancement of novel object exploration induced by Quinpirole (1 and 5 µg) and SB 277-011 (0.5 and 1 µg), but not by SKF 81297 (0.2 and 0.5 µg), was substantially attenuated in animals subjected to the CMS procedure. CONCLUSIONS: These data provide evidence that the regulation of recognition memory by the limbic D2 and D3 receptors is under a potent influence of prolonged stress, and are discussed in terms of their implications for understanding the neurobiological mechanisms underlying pathology of affective and psychotic diseases.
Despite many years of research on depression the mechanism of the disorder remains elusive. Many studies are focused on dysfunction of central monoaminergic systems and some evidence exist for the role of α1-adrenoceptor (α1-AR). There are three subtypes of this receptor - α1A, α1B and α1D, which are widely distributed in brain. The aim of this study was to assess the expression of all three α1-AR, both at the mRNA and at the protein level in the hippocampi of male Wistar rats, subjected to the chronic mild stress (CMS) procedure followed by treatment with antidepressant drug, imipramine (IMI). Five groups of animals were studied: sham-saline; stress-saline; sham-IMI; stress-IMIresponders and stress-IMI-non-responders. The latter included the stressed animals resistant to IMI treatment as indicated by anhedonia test. The mRNA level was measured using qRT-PCR and SybrGreen dye, and the protein level was assessed by Western blotting. We found that mRNA expression of all α1-AR subtypes was significantly elevated only in the IMI-non-responders group (α1A-AR by 76%; α1B-AR by 96%; α1D-AR by 50%, vs. shamsaline). Moreover, stress alone caused an increase in α1A-AR mRNA (by 41%) though the effect was statistically insignificant. Changes found in the protein level were less pronounced. The only difference between IMI-responders and non-responders was found in α1A receptor protein that was decreased by 73% vs IMIresponders. The level of α1D protein was elevated in all IMI treated groups (by about 79%, vs. sham-saline) and the change occurred independently on stress procedure. No change in the α1B protein was found. Our results indicate that although α1A-AR and α1D-AR are involved in mechanism of IMI action, only the α1A receptor seems to be engaged in the phenomenon of resistance to IMI treatment. Supported by a grant POIG.01.01.02-12-004/09-00 financed by European Regional Development Fund.
Several studies have suggested that modulation of the glutamatergic system via metabotropic glutamate receptors (mGlu) could be a new, efficient way to achieve antipsychotic-like effects. Such an activity was shown for mGlu2/3 and mGlu5 receptor agonists/positive modulators, as well as for ACPT-I or LSP1-2111, a non-selective mGlu group III receptors orthosteric agonists. Herein, we report the pharmacological actions of Lu AF21934 and Lu AF32615, a novel, selective and brain-penetrant positive allosteric modulators (PAMs) of the mGlu4receptor with proven anxiolytic, but not antidepressant-like activity, in several tests reflecting positive, negative and cognitive symptoms of schizophrenia in rodents. MK-801- and amphetamine-induced hyperactivities, as well as DOI-induced head twitches in mice were used as models for positive symptoms. Furthermore, the effect of Lu AF21934 on DOI-induced frequency of spontaneous excitatory postsynaptic currents (EPSCs) in slices from mouse brain frontal cortices was investigated. The MK-801 induced disruption of social interaction and of spatial delayed alternation in rats were used as models for negative and cognitive symptoms, respectively. Lu AF21934 (0.1, 0.5, 2 and 5 mg/kg) and Lu AF32615 (2, 5 and 10 mg/kg) dose-dependently inhibited both MK-801 and amphetamine-induced hyperactivities. Concomitantly, Lu AF 21935, an inactive enantiomer of Lu AF21934, was not effective. Moreover, the drugs antagonized DOI-induced head twitches in mice. DOI-induced increased frequency of spontaneous EPSCs was also decreased by Lu AF21395 and Lu AF32615. The MK-801-induced disruption in the social interaction test, measured as number of episodes and total time of episodes between two rats, was abolished by Lu AF21394 at a dose of 0.5 mg/kg and Lu AF32615 at a dose of 10 mg/kg. In the delayed spatial alternation test, the effective doses of Lu AF21934 were 1 and 2 mg/kg, and the AF32615 was active at a dose of 10 mg/kg. Altogether, we propose that mGlu4 receptor can be consider as promising target for the development of novel antipsychotic drugs, acting as a positive allosteric modulators of the receptor.
The effect of antidepressant drugs on tumour progress in animals models of stress is very poorly recognized. Further more a role of susceptibility to stress in modulatory effect of antidepressant drug on tumour growth have not been studied. The aim of present study was to establish the effect of individual reactivity to stress and prophylactic two weeks desipramine administration on metastatic colonization of MADB 106 cells in lungs of Wistar rats. Rats were subjected by three weeks to chronic mild stress (CMS) model of depression and high-reactive and non-reactive rats were selected. Three months after CMS termination high-reactive and non-reactive animals were further subdivided: for two additional weeks the rats received daily injection of desipramine or saline. Tumor cells were injected two hours after last desipramine or saline administration. In stress-reactive, vehicle treated rats increase of number of lung metastasis in comparison to stress non-reactive, vehicle treated rats were observed. On the other hand chronic desipramine pretreatment signifi cantly increased survival rate and diminished number of lung metastasis in stress-sensitive animals although did not show such effect in stressresistant animals. Increase in rate of animal survival and decrease in lung metastasis can be connected with stimulatory effect of chronic desipramine pretreatment on NK cell activity. This study was supported by grant N40109732/2074 from Poland’s MS and HE.
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