We employed three genotypes of GAD 65, wildtype (GAD 65 +/+), heterozygous (GAD 65 +/-) and knockout (GAD 65 -/-) to investigate the role of GAD 65 in survival of pancreatic islets. We analyzed the mRNA expression of pro-survival proteins including Bcl2 and Bax in pancreas of wildtype, heterozygous and knockout using Reverse Transcriptase Polymerase Chain Reaction (RTPCR). The level of expression of Bcl2 mRNA was down regulated in knockout mice pancreas and Bax to Bcl2 ratio was found higher in knockout mice pancreas suggesting higher cell death rate. However, further studies are required to recognize and understand the specific connections between apoptotic pathways and GAD 65 in pancreatic islets. / by Neeta Kumari. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Brain glutamic acid decarboxylase 65 (GAD65) catalyzes the rate-limiting step in the biosynthesis of the major inhibitory neurotransmitter-amino butyric acid (GABA) from the substrate L-glutamic acid. Severe lapse in GABA neurotransmission is one of the etiologies documented in the manifestation of certain neurodegenerative diseases such as epilepsy, Parkinson's disease, Huntington's disease etc. Because GAD65 synthesizes GABA, any modulation of GAD65, therefore, has direct implications on the quanta of GABA released at the synapse. Hence, the major objective of this study was to focus on the regulation of GAD65, with special emphasis on investigating the proteolytic cleavage of fGAD65. Previously, we have shown in vitro that GAD65 was cleaved to form its truncated form (tGAD65), which was more active than the full length form (fGAD65). The enzyme responsible for cleavage was later identified as calpain. Calpain is known to cleave its substrates either under a transient physiologica l stimulus or upon a sustained pathological insult. However, the precise role of calpain cleavage of fGAD65 is poorly understood. In this study, we examined the cleavage of fGAD65 under a range of conditions encompassing both physiological and pathological aspects, including rats under ischemia/reperfusion insult, rat brain synaptosomes or primary neuronal cultures subjected to excitotoxic stimulation with KCl. It was observed that the formation of tGAD65 progressively increased with increasing stimulus concentration. More importantly, cleavage of synaptic vesicle (SV) - associated fGAD65 by calpain was demonstrated, and the resulting tGAD65 harboring the active site of the enzyme was detached from the SVs. Vesicular uptake of the newly synthesized GABA into the SVs was found to be reduced in calpain treated SVs. Furthermore, we also observed that the levels of tGAD65 in the focal cerebral ischemic rat brain tissue increased corresponding to the elevation of local glutamate indica / d by in vivo micro dialysis. Based on these observations, we conclude that calpain cleavage of fGAD65 occurs under pathological conditions. / by Chandana Buddhala. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Group II metabotropic glutamate receptors (mGluR2/3) are predominately presynaptically located Gi/o coupled receptors that are highly expressed in the cortex, nucleus accumbens, amygdala, and hippocampus. Previous studies suggest that group II mGluRs are involved in regulating ethanol (EtOH) consumption and seeking following extinction (Backstrom and Hyytia, 2005; Kufahl, et al., 2011). The sipper tube model, which allows for procedural separation of seeking and consumption, was used to further clarify the role of mGluR2/3 in EtOH-seeking and consumption. The non-selective group II mGluR agonist LY379268 (LY37) and selective mGluR2 positive allosteric modulator (PAM) BINA were used to determine the relative contribution of mGlu2 and mGlu3 receptors on EtOH seeking and consumption. Following characterization of the agonist and PAM on EtOH reinforcement, a microinjection study was performed examining the effect of blockade of nucleus accumbens core mGluR2/3 on systemic agonist induced suppression of EtOH-seeking. Methods: For the systemic agonist/PAM experiments, separate groups of male Wistar rats [n=8-9 group; LY37 (0-2.0 mg/kg) and BINA (0-20 mg/kg)] were trained to complete a response requirement (RR) of 10 lever presses that resulted in access to 10% EtOH or 2% sucrose (in separate groups) for a 20-minute drinking period. For consummatory testing, animals received weekly drug injections with a RR1. The RR was then increased over sessions to a RR20. For appetitive testing, animals received weekly drug injections followed by a non-reinforced extinction session. To determine effects of blockade of NAc core mGluR2/3 receptors on agonist-induced suppression of EtOH-seeking, a separate group of male Wistar rats (n=15) was trained to complete a RR10 for access to 10% EtOH. Animals were surgically implanted with bilateral guide cannulae terminating 1mm above the NAc core. Following recovery, animals received four sets of microinjections in a balanced design (systemic vehicle + core vehicle, systemic LY37 + core vehicle, systemic LY37 + core LY34, and systemic vehicle + core LY34). A final non-balanced microinjection of LY37 was then performed. Results and Conclusions: Systemic administration of the mGluR2/3 agonist LY37 significantly reduced EtOH- and sucrose- seeking with no systematic effect on locomotion. Systemic administration of the selective mGluR2 PAM BINA had no significant effect on either seeking or consumption. These findings suggest that modulation of glutamatergic neurotransmission by a systemic mGluR2/3 agonist, but not allosteric modulation of mGluR2, significantly reduces reinforcer seeking. Intra- accumbens core administration of LY37 significantly reduced EtOH-seeking, suggesting a role of NAc core mGluR2/3 modulation in EtOH-seeking during maintenance drinking. Systemic administration of LY37 was also found to significantly reduce sucrose consumption and body weight 24-hours following systemic administration, meriting further examination of the role of mGluR2/3 receptors on feeding behavior.

Drugs which upregulate astrocyte glutamate transport may be useful neuroprotective compounds by preventing excitotoxicity. We set up a new system to identify potential neuroprotective drugs which act through GLT-1. Primary mouse striatal astrocytes grown in the presence of the growth-factor supplement G5 express high levels of the functional glutamate transporter, GLT-1 (also known as EAAT2) as assessed by Western blotting and (3)H-glutamate uptake assay, and levels decline following growth factor withdrawal. The GLT-1 transcriptional enhancer dexamethasone (0.1 or 1 muM) was able to prevent loss of GLT-1 levels and activity following growth factor withdrawal. In contrast, ceftriaxone, a compound previously reported to enhance GLT-1 expression, failed to regulate GLT-1 in this system. The neuroprotective compound riluzole (100 muM) upregulated GLT-1 levels and activity, through a mechanism that was not dependent on blockade of voltage-sensitive ion channels, since zonasimide (1 mM) did not regulate GLT-1. Finally, CDP-choline (10 muM-1 mM), a compound which promotes association of GLT-1/EAAT2 with lipid rafts was unable to prevent GLT-1 loss under these conditions. This observation extends the known pharmacological actions of riluzole, and suggests that this compound may exert its neuroprotective effects through an astrocyte-dependent mechanism.