Doncho P. Uzunov

Permissive role of brain allopregnanolone content in the regulation of pentobarbital-induced righting reflex loss

Allopregnanolone [3alpha-hydroxy-5alpha-pregnan-20-one] (ALLO), a potent neurosteroid that positively modulates gamma-aminobutyric acid (GABA) action at various GABA(A) receptor subtypes is synthesized in nanomolar concentrations and stored non uniformly in various brain structures of mammals. We have measured brain ALLO content and its precursors by negative ion chemical ionization-mass-spectrometry after purification and separation of the different steroids with HPLC and gas chromatography. Our procedure measures steroids in the femtomolar range with structural information and unsurpassed selectivity. We were able to establish an association between the decrease in content of ALLO in mouse brain cortex elicited by either long-lasting social isolation or by the administration of 17beta-17 [bis (1-methylethyl) amino carbonyl] androstane-3,5-dilene-3-carboxylic acid (SKF 105111). an inhibitor of Types I and II 5alpha reductases, and the shortening of the righting reflex loss elicited by pentobarbital (PBT). SKF 105111 added to cortical brain slices in concentrations up to 10(-5) M failed per se to alter GABAergic currents or their potentiation by PTB recorded from pyramidal neurons. Fluoxetine (1.45 or 2.9 micromol/kg i.p.) doses that fail to change the PTB-induced loss of righting reflex and the level of brain ALLO in group-housed mice normalized both parameters in socially-isolated mice. In addition, we could detect both fluoxetine actions in socially isolated mice pretreated with doses of p-chlorophenylalanine (1.2 mmol/kg i.p. at 72, 48, and 24 h) that substantially inhibit brain serotonin 5HT synthesis as shown by an 80% drop of brain 5HT content. These studies for the first time have provided evidence suggesting that the endogenous cortical stores of ALLO physiologically upregulate GABAergic tone and by such a mechanism play a permissive or facilitatory role on the PTB-induced loss of the righting reflex. In the absence of such a permissive physiological influence by endogenous ALLO, the righting reflex inhibition by PTB is down regulated.

Simultaneous detection of glutamic acid decarboxylase and reelin mRNA in adult rat neurons using in situ hybridization and immunofluorescence

The combination of in situ hybridization and immunocytochemical technique is an important tool to detail the biochemical phenotype of individual neurons. In this work, we have developed a double fluorescence method to show the presence of reelin mRNA in GABAergic cells. This was achieved by demonstrating the colocalization of glutamic acid decarboxylase67, the synthesizing enzyme for GABA, with the mRNA for reelin, a novel factor involved in brain development and possibly the maintenance of the synaptic organization of layered structures in adult brain. The results demonstrated that reelin is expressed primarily in GABAergic cells in the adult rat cerebrum, but not in the cerebellum.

223. Reelin and GAD67 downregulation and psychosis vulnerability

nia patients. Working memory deficits are present in about 80% of schizophrenia patients, resistant to anti-psychotic drug treatments and associated with social functioning. In the first study, we examined the effects of affective salience of the target on spatial working memory. Increasing the salience of the target facilitates working memory in schizophrenia patients and the affective valence of the target contributes to the improvement. In Study 2, we examined the role of social (human) vs. non-social (computer) reinforcement on working memory and found that only the human, social reinforcement facilitates working memory in schizophrenia patients. In Study 3, the role of positive mood arousal on working memory was examined. We manipulated the mood arousal by showing film clips. Salivary cortisol levels, heart rate, and blood pressure were measured. Facilitation of working memory in schizophrenia occured after they viewed a film clip which invites participation by the patient but not after viewing a comic clip which does not invite participation. These results suggest that affective and social modulation of working memory function is significant in schizophrenia and point to the importance of integrating “affect” and “cognition” in studies of frontal lobe function.

408. Putative role of allopregnanolone in psychiatric disorders

each MRSI voxel was also analyzed for amounts of gray matter, white matter, hyperintense white matter, and CSF using in-house software (SICORE) in order to obtain tissue volume corrected NAA concentration estimates. Repeated measures ANOVA revealed that compared to the control group, the patients with bipolar I disorder demonstrated: 1) decreased DLPFC NAA bilaterally (p 5 0.0004), 2) decreased prefrontal white matter NAA bilaterally (p 5 0.0014), 3) increased thalamic NAA bilaterally (p 5 0.01), and 4) no significant group or lateralized differences in voxel tissue composition for any of the regions studied. Thus, the NAA alterations in the bipolar group were not due to any differences in voxel tissue heterogeneity between groups. The DLFPC reduction in NAA suggests neuronal loss/dysfunction whereas the observed prefrontal white matter NAA reduction is evidence for compromised axonal integrity that may result in functional disconnection of prefrontal-thalamic pathways. Increased thalamic NAA may represent neuronal hypertrophy, neuronal hyperplasia, or abnormal synaptic/dendritic pruning. The results definitely suggest that neuronal/axonal integrity of DLFPC-thalamic pathways is abnormal in bipolar I disorder.