Glutamate Signaling Proteins and Tyrosine Hydroxylase in the Locus Coeruleus of Alcoholics

It has been postulated that alcoholism is associated with abnormalities in glutamatergic neurotransmission. This study examined the density of glutamate NMDA receptor subunits and its associated proteins in the noradrenergic locus coeruleus (LC) in deceased alcoholic subjects. Our previous research indicated that the NMDA receptor in the human LC is composed of obligatory NR1 and regulatory NR2C subunits. At synapses, NMDA receptors are stabilized through interactions with postsynaptic density protein (PSD-95). PSD-95 provides structural and functional coupling of the NMDA receptor with neuronal nitric oxide synthase (nNOS), an intracellular mediator of NMDA receptor activation. LC tissue was obtained from 10 alcohol-dependent subjects and eight psychiatrically healthy controls. Concentrations of NR1 and NR2C subunits, as well as PSD-95 and nNOS, were measured using Western blotting. In addition, we have examined tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of norepinephrine. The amount of NR1 was lower in the rostral (-30%) and middle (-41%) portions of the LC of alcoholics as compared to control subjects. No differences in the amounts of NR2C, PSD-95, nNOS and TH were detected comparing alcoholic to control subjects. Lower levels of NR1 subunit of the NMDA receptor in the LC implicates altered glutamate-norepinephrine interactions in alcoholism

Elevated Levels of NR2A and PSD-95 in the Lateral Amygdala in Depression

Compelling evidence suggests that major depression is associated with dysfunction of the brain glutamatergic transmission, and that the glutamatergic N-methyl-d-aspartate (NMDA) receptor plays a role in antidepressant activity. Recent post-mortem studies demonstrate that depression is associated with altered concentrations of proteins associated with NMDA receptor signalling in the brain. The present study investigated glutamate signalling proteins in the amygdala from depressed subjects, given strong evidence for amygdala pathology in depression. Lateral amygdala samples were obtained from 1314 pairs of age- sex-, and post-mortem-interval-matched depressed and psychiatrically healthy control subjects. Concentrations of NR1 and NR2A subunits of the NMDA receptor, as well as NMDA receptor-associated proteins such as post-synaptic density protein-95 (PSD-95) and neuronal nitric oxide synthase (nNOS) were measured by Western immunoblotting. Additionally, levels of enzymes involved in glutamate metabolism, including glutamine synthetase and glutamic acid decarboxylase (GAD-67), were measured in the same amygdala samples. NR2A protein levels were markedly and significantly elevated (+115%, p=0.03) in depressed subjects compared to controls. Interestingly, PSD-95 levels were also highly elevated (+128%, p=0.01) in the same depressed subjects relative to controls. Amounts of NR1, nNOS, glutamine synthetase, and GAD-67 were unchanged. Increased levels of NR2A and PSD-95 suggest that glutamate signalling at the NMDA receptor in the amygdala is disrupted in depression

Dopamine Receptor Gene Expression in Human Amygdaloid Nuclei: Elevated D4 Receptor mRNA in Major Depression

Previous findings from this laboratory demonstrating changes in dopamine (DA) transporter and D2 receptors in the amygdaloid complex of subjects with major depression indicate that disruption of dopamine neurotransmission to the amygdala may contribute to behavioral symptoms associated with depression. Quantitative real-time RT-PCR was used to investigate the regional distribution of gene expression of DA receptors in the human amygdala. In addition, relative levels of mRNA of DA receptors in the basal amygdaloid nucleus were measured postmortem in subjects with major depression and normal control subjects. All five subtypes of DA receptor mRNA were detected in all amygdaloid subnuclei, although D1, D2, and D4 receptor mRNAs were more abundant than D3 and D5 mRNAs by an order of magnitude. The highest level of D1 mRNA was found in the central nucleus, whereas D2 mRNA was the most abundant in the basal nucleus. Levels of D4 mRNA were highest in the basal and central nuclei. In the basal nucleus, amounts of D4, but not D1 or D2, mRNAs were significantly higher in subjects with major depression as compared to control subjects. These findings demonstrate that the D1, D2 and D4 receptors are the major subtypes of DA receptors in the human amygdala. Elevated DA receptor gene expression in depressive subjects further implicates altered dopaminergic transmission in the amygdala in depression

THE STUDY OF ADSORPTION AND DESORPTION OF ANTIBIOTICS ON THE SURFACE OF NANOPARTICLES

Nanotechnology is a field that is gaining more and more importance in the modern world. It uses a particle size of between a few dozen to a few hundred nanometers, or 10-9 meters. It is noted that the use of nanospheres (balls with a diameter of from several to several hundred nm) as carriers of drugs gives an opportunity for their controlled and sustained release. (1,2) Nanospheres as a potential drug carrier for sustained release may enhance the effectiveness of antibiotics. In order to examine the effects of antibiotics with nanospheres an attempt was made to deposit on them three drugs differing in chemical structure. These were chloramphenicol, gentamicin and ceftazidime. The aim of this study was to determine the degree of adsorption of the drug on the surface of nanospheres and to examine the process of desorption from the surface of silica nanoparticles. The results of the study indicate that in the case of chloramphenicol it is essentially a process of chemisorption, and for gentamicin and ceftazidime both physical and chemical adsorption, without there being any clearly defined relationship between this two processes. The purpose of the nanospheres as drug carriers is to obtain controlled and prolonged exposure to the drug. The amount of adsorbed substance depends primarily on its structure. Ceftazidime, as the compound with the highest number of double bonds, and a large number of groups to form hydrogen bonds (carbonyl groups, amino groups), adsorbed to the greatest extent

Low Levels of Tyrosine Hydroxylase in the Lateral Nucleus of the Amygdala in Major Depression

The lateral and basal nuclei of the amygdala receive dopaminergic projections from the ventral tegmental area and substantia nigra, and noradrenergic projections from the locus coeruleus (LC). Previously, we demonstrated postmortem indices of altered dopaminergic (amygdala) and noradrenergic (LC) neurochemistry in subjects with major depressive disorder (MDD). For example, decreased levels of dopamine transporter were observed in the amygdala in MDD, while concentrations of tyrosine hydroxylase (TH) were elevated in the LC in MDD. The present study investigated the quantitative distribution of TH in nuclei of the human amygdala from 5 control subjects, and measured amounts of TH in specific amygdaloid nuclei and the LC from 8-10 matched pairs of MDD and psychiatrically normal control subjects. Matched pairs included 3 females and 7 males (controls and MDD), average ages of 50±5 y (controls) and 51±5 y (MDD), average postmortem intervals of 16±2 h (controls) and 21±1 h (MDD), and average pH values of 6.58±0.08 (controls) and 6.59±0.09 (MDD). The lateral, basal, accessory basal, and central nuclei of the amygdala and the LC were punched from frozen sections of postmortem brain. TH-immunoreactivity was measured by quantitative Western blotting. In normal control subjects, TH levels in the LC were between 3000- and 4000-fold higher than TH levels in the nuclei of the amygdala. Within the amygdala, amounts of TH were highest in the basal and central nuclei, and lowest in the lateral nucleus. TH levels in the basal nucleus were highly variable across subjects. TH levels were significantly lower (-50%) in the lateral amygdaloid nucleus in MDD subjects as compared to control subjects. In contrast, TH levels in the LC were significantly higher (+75 %) in MDD subjects. This report is the first demonstration of altered TH levels in the human amygdala. The direction of change associated with MDD of TH in the lateral nucleus of the amygdala was opposite to that found in the LC. Whether abnormal amounts of TH in the amygdala are a result of altered dopaminergic or noradrenergic input to the amygdala requires further study

NMDA Receptor and Associated Intracellular Proteins in Amygdala and Hippocampus in Depression

Accumulating evidence suggests dysfunction of the glutamate signaling system in major depressive disorder. Previously, we observed elevated levels of NR2C subunit of N-methyl-D-aspartate receptor (NMDAR) and lower levels of neuronal nitric oxide synthase (nNOS), intracellular mediator of NMDAR activation, in the noradrenergic locus coeruleus in depressed subjects (Karolewicz et al. 2004, 2005). The aim of the present study was to investigate potential abnormalities in the NMDAR signaling molecules in the amygdala and hippocampus from the same depressed subjects. Tissue samples containing the lateral nucleus of amygdala, and hippocampal dentate gyrus were obtained from 10 -11 matched pairs of depressed subjects and healthy controls. Subjects were matched for age, sex, brain pH, and postmortem interval. Changes in concentration of NMDAR subunits NR1 and NR2 as well as intracellular associated proteins, neuronal nitric oxide synthase (nNOS) and postsynaptic density protein (PSD-95), that might occur in depression were assessed by immunoblotting. NR1 subunit immunoreactivity appeared as a prominent band at 120 kDa; NR2A as a band at 180 kDa; PSD-95 and nNOS immunoreactivities appeared as bands at 95 kDa and 155 kDa, respectively. The overall amount of NR1 and nNOS was normal in subjects diagnosed with depression as compared to controls. Amounts of PSD-95 were significantly higher in the amygdala (+115%, p\u3c0.05) and hippocampus (+34%, p\u3c0.05), respectively. The level of NR2A subunit was elevated in the amygdala (+51%) in depressed subjects as compared to controls. Our data indicate that glutamatergic signaling is abnormal in depression. Higher levels of NMDA receptor subunits and its associated protein may represent an adaptive response to decreased synaptic release of glutamate. This hypothesis is in agreement with postmortem and neuroimaging findings of altered glutamatergic transmission in depression. Further studies of the glutamatergic signaling system may lead to the development of novel therapeutics for the treatment of depressive disorder