Central Nervous System Agents in Medicinal Chemistry (Formerly Current Medicinal Chemistry - Central Nervous System Agents) - Volume 11, Issue 3, 2011

Depression is a disorder that can be classified in the categories of non-organic psychiatric disorders and mood disorders. Mood tone is an important psychic function involved in the adaptation to both our internal and external world. It is flexible, that is, it goes up when we are in positive and favorable conditions, but it goes down when we are in negative and unpleasant states. We can define depression as a condition when mood tone loses its flexibility, it goes down and it's no longer influenced by favorable external events. In fact, depression is characterized by changes in the way how the affected individual thinks, feels and acts. Even if this change occurs gradually, a depressed subject is not the same as before. For example, a brilliant student could be persuaded to be not able to finish his studies; an affectionate mother could start to neglect her sons; an enterprising worker could lose every interest for his activity. Moreover, a depressed person doesn't care of his aspect or of himself. The surviving instinct could leave place to the desire to stop his own life. The most evident characteristic of depression in the adulthood is a sad mood, a gloomy solitary and apathetic attitude. A depressed subject could cry also with no apparent reason, he could have difficulty falling asleep or he could wake up very early in the morning and no longer returns to sleep. Or, instead, he could sleep more than usually and he could feel tired persistently. He could lose appetite and weight, or, in some cases, he could eat much more than usually and he could gain weight. Typically, a depressed person feels himself in a extremely negative way, he could think to be hopeless and helpless and he often condemns himself for small guilty. A depressed subject is pessimistic about himself and his own future; he loses interest in all what happens around him and he gets no satisfaction from the activities that before were pleasant. Some persons can be depressed also if they don't show evident signs of depression, but they complain for physical symptoms or they abuse of alcohol or other substances. It has been estimated that in the industrialized Western world one to six persons has a depressive episode at least once during his life; at present, the incidence of depression in the general population is around 5% with clear cut prevalence in the female sex. This leads to high social costs: behind the short-term inability, we have to consider also the long term inability (it has been estimated that, in 2020, depression will represent the second most frequent cause of permanent inability) as well as the suicide risk, the proved major susceptibility of depressed subjects to various non-psychiatric pathologies and the increased rate of premature deaths of depressed individuals as compared to the general population. The present work not only evaluates the drugs used for the treatment of depression, but it focuses also on those studies that investigated the efficacy of a second generation drug: Duloxetine that has a higher selectivity of action and a better tolerability profile as compared to first generation medications. These characteristics make Duloxetine the most effective therapeutic choice to improve both psychological and somatic symptoms of depression in order to get higher rates of symptomatic remission on depressive episodes.

Crush-syndrom (CS) was characterized by Bywaters E.G.L. in 1941 after London blitz. The soft tissues is followed by acute hemodynamic shock, myoglobinuria, acute renal insufficiency, and lethal endotoxicity. Data of CS pathogenesis study has shown that the largest changes in Crush occur during decompression and are accompanied by acute alteration of brain protein synthesis and strong morphological changes of brain structures. The period of decompression might be characterized by the proteolytic breakdown of the myoglobine and formation of toxic peptides. In our current work we have identified four newly formed peptides in the brain of the animals subjected to the experimental muscle tissue injury. Our investigations related with the CS experimental model have demonstrated that during the 2-hours compression protein synthesis was decreased in cytosol (32,7%) and mitochondria (49%), after 5-h compression there were registered non-significant changes in the level of protein synthesis. Intraperitoneal administration of Proline-rich peptide, ((PRP), 1 mcg/100g weight of rats), originating from proteolysis of C-terminal glycoprotein a neurophysin II along with vasopressin and oxytocin and transferring from the hypothalamus to the neurohypophysis by axonal transport, initiates activation of the protein synthesis in all studied cellular subcomponents of brain cells. The positive effect of the peptide is conditioned, most probably, by activation of the immune system and adaptation mechanisms, including mobilization of endogen-protective mechanisms of the organism.

The endocannabinoid system comprises amides, esters and ethers of long chain polyunsaturated fatty acids. Narachidonoylethanolamide (anandamide; ANA) and 2-arachidonoylglycerol (2-AG) are endogenous cannabinoids (endocannabinoids) ligands for the cannabinoid family of G-protein-coupled receptors named CB1 and CB2. Endocannabinoids are released upon demand from lipid precursors in a receptor-dependent manner and behave as retrograde signaling messengers, as well as modulators of postsynaptic transmission, interacting with other neurotransmitters systems. The two principal enzymes that are responsible for the metabolism of ANA and 2-AG are fatty acid amide hydrolase and monoacylglycerol lipase, respectively. Pharmacological experiments have shown that the administration of endocannabinoids induce cannabimimetic effects, including sleep promotion. This review will focus on some of the current evidence of the pharmacological potential of the endocannabinoid system on sleep modulation.

A major component in the protection of the brain against blood-borne toxic influences is the multispecific efflux pump P-glycoprotein. This pump, a 170 kD protein, located at the luminal side of the capillary endothelial cells, has a large capacity and is capable of extruding a wide array of structurally divergent substrates. The brain uptake of the majority of antidepressants and antipsychotics, as well as many other psychotropic drugs and endogenous compounds is hampered by the activity of P-glycoprotein. In this review we discuss the current state of knowledge concerning the role of Pglycoprotein on pharmacokinetics of psychiatric drugs and the impact of modulation of P-glycoprotein on major psychiatric disorders. Relevant issues in reference to the function of P-glycoprotein and other efflux pumps in the blood-brain barrier related to mood disorders and schizophrenia are addressed, such as a possible role of P-glycoprotein as a susceptibility factor in depressive disorders and psychotic disorders.

The development of neuronal apoptosis depends on an intrinsic transcriptional program. By DNA microarray technology, we have previously implicated a number of genes in different paradigms of neuronal apoptosis. In the present study, we investigated the spatiotemporal pattern of expression of two of these genes, gastric inhibitory polypeptide (Gip) and its receptor (Gipr) in the rat central nervous system. The levels of their transcripts were measured with real-time quantitative polymerase chain reaction and in situ-hybridization. Widespread expression of Gip and Gipr was found in adult rat brain, whereas during postnatal cerebellum development, they were highly expressed in the external and internal granule layer, and in Purkinje cells. To investigate the possible biological function of Gip we examined its effects in vitro. Addition of Gip to cultured cerebellar granule neurons reduced the extent of apoptotic death induced by switching the growing medium from 25 to 5 mM K+. This neurotrophic effect was mimicked by that of PACAP38 and IGF1. We conclude that Gip acts as an endogenous neurotrophic factor and supports neuronal survival.

Objective: Cefepime neurotoxicity usually occurs in patients with renal impairment. The aim of this study was to evaluate the neurotoxicity of cefepime administered by continuous intravenous infusion during treatment of nosocomial infections in neurological patients with normal renal function. Methods: This was an open pilot study of neurological patients with infections caused by cefepime sensitive bacteria. Patients had baseline neurological assessment and electroencephalogram (EEG). Cefepime plasma concentrations were determined 48 hours after infusion was initiated and at end of treatment (EOT). Results: Eleven patients were included. These were diagnosed with a brain tumor (9), cerebrovascular disease (1) and polyneuropathy (1). Infections were surgical site infection in 5, clinically defined nosocomial pneumonia in 4, and bacterial meningitis associated to postoperative CSF fistula in 2. Gram-negative organisms were isolated in 10 patients. Cefepime dose was 2 g/day in 9 patients and 4 g/day in 2. Mean cefepime plasma concentration at 48h was 13.6 ± 2.0 µg/mL (range 4.6 to 24.5 µg/mL), at EOT was 11.9 ± 1.8 µg/mL (range 3.0 to18.9 µg/mL ). EEG interpreted by two experts showed at baseline alpha background rhythm in 5 and theta-alpha rhythm in 6 patients. On EEG at EOT background rhythm was alpha in 4 and theta-alpha in 7, one patient presented isolated sharp and slow wave activity. No mental status changes or seizures occurred and all infections resolved. Conclusion: Significant EEG change was observed in 1of 11 patients. A preserved mental status may correlate with cefepime safety in neurological patients with normal renal function during cefepime treatment.

Dysfunction of serotoninergic neurotransmission is known to be involved in the pathophysiology of major depression. The molecules that enhance the level of serotonin either via blocking serotonin reuptake or through inhibition of its metabolism are effective antidepressants. With this as the basis, a group of new molecules that supposedly effect serotoninergic neurotransmission were designed and tested. The new molecular entities (NME-2, NME-5, NME-16 and NME- 24) are active in animal models of behavioral despair. In the present study, the binding of these new NMEs to the serotonin transporter protein (SERT) has been modeled and their activity correlated with the behavioral pattern observed in the mouse forced swim test (FST) model. The putative binding orientations of the NMEs have been identified by docking the molecules into the active site of the SERT. A 3D model of the SERT active site was constructed using comparative protein modeling principles with the X-ray structure of the leucine transporter (LeuT) as template. 3D-QSAR models based on the CoRIA formalism were generated from the experimental data and docking scores for eight novel SERT inhibitors. The CoRIA models highlight the salient features for effective binding of NMEs to the serotonin transporter and are also able to predict pKd values. Based on the significant correlation between the anti-immobility effect seen in the mouse FST study and the binding energies obtained from the docking study along with insights from the interaction patterns with the receptor obtained from the docking, the CoRIA models can be used to suggest structural modifications that can help in optimization of the SERT inhibition. Experimental evidence shows that the NMEs are highly efficacious and could be developed into potential antidepressants.