Methylazoxymethanol (MAM)-induced brain lesion and oral dyskinesia in rats

The effects of methylazoxymethanol (MAM)-induced brain lesions on vacuous chewing movements (VCM) were examined in rats given chronic haloperidol treatment (0.1 or 1 mg/kg/day) for 18 months. At the end of the experiment striatal, pallidal, and nigral activities of glutamate decarboxylase (GAD) were measured. MAM-lesioned rats had an elevated rate of VCMs compared to unlesioned controls. This effect was stable during the whole 18-month experiment. In unlesioned control rats chronic haloperidol produced a gradual increase in VCM rates, but this effect was not further exacerbated in MAM-lesioned animals. After chronic haloperidol treatment with the higher dose (1 mg/kg/day) GAD activity was reduced in substantia nigra (-20%), globus pallidus (-35%), and striatum (-26%) of unlesioned rats. MAM caused a reduction of GAD activity in substantia nigra (-29%) and globus pallidus (-29%). Chronic haloperidol did not influence these effects of MAM-induced lesion. The present results show that a MAM-induced brain lesion, in contrast to cortical ablations, cannot be used to amplify the haloperidol-induced VCM increase or influence the nigral GAD activity in a rat model for tardive dyskinesia.     

GABAergic neurons in the mammalian inferior olive and ventral medulla detected by glutamate decarboxylase immunocytochemistry.

Neurons containing glutamic acid decarboxylase (GAD) (presumed GABAergic neurons) were mapped by immunocytochemistry in the ventral medulla of rat, rabbit, cat, rhesus monkey, and human, with emphasis on the inferior olive. In all species, three categories of GABAergic neurons were identified: periolivary neurons in the gray matter and the white matter surrounding the inferior olive, internuclear neurons located in the white matter between the subnuclei of the inferior olive, and intranuclear neurons located within the olivary gray matter. The intranuclear GABAergic neurons of the inferior olive had a characteristic morphology which differed from non-GABAergic olivary neurons; they were usually smaller, and, wherever their processes were stained, they had radiating, sparsely branching dendrites. They were also usually distinguished from the other GABAergic neurons by their smaller size. The intraolivary GABAergic neurons constituted only a minor proportion of the total olivary neuronal population, but they were concentrated in regions of the olive that varied by species. In the rat, they were situated in the rostral tip of the medial accessory olive and in the caudal subdivision of the dorsal accessory olive, while in the rabbit, they were located in the caudal two-thirds of the medial accessory olive, in the dorsal cap, and in the ventral lateral outgrowth. Such neurons were extremely rare in the cat; only a few were found in the rostral parts of the principal olive, the medial accessory olive, and the dorsal accessory olive. In the rhesus monkey, the principal olive and the lateral region of the rostral medial accessory olive contained most of the intranuclear GABAergic neurons, but some were also present in the dorsal accessory olive. In the human, such neurons occurred in the principal olive, the dorsal accessory olive and the rostral medial accessory olive, but as in the rhesus monkey, most were observed in the principal olive.     

Glutamic acid decar☐ylase activity decreases in mouse neocortex after lesions of the basal forebrain

Glutamic acid decar☐ylase (GAD) activity was measured in the cerebral cortex of animals after acute and chronic lesions to basal forebrain cholinergic nuclei. Such lesions were shown to result in an extensive depletion of cholinergic markers in parietal cerebral cortex. A statistically significant 30% decrease in GAD activity was first detected at 6 weeks postlesion and was still measurable 8 months after the lesion. These results suggest that cholinergic inputs to cortex indirectly or directly influence GABAergic transmission in cortex.     

Biphasic Response of Spinal GABAergic Neurons after a Lumbar Rhizotomy in the Adult Rat

The expression of γ-aminobutyric acid (GABA) and of the isoforms of the enzyme involved in its synthesis, glutamic acid decarboxylase (GAD), is modified in several rat brain structures in different injury models. The aim of the present work was to determine whether such plasticity of the GABAergic system also occurred in the deafferented adult rat spinal cord, a model where a major reorganization of neural circuits takes place. GABAergic expression following unilateral dorsal rhizotomy was studied by means of non-radioactive in situ hybridization to detect GADs₆₇ mRNA and by immunohistochemistry to detect GAD₆₇ protein and GABA. Three days following rhizotomy the number of GAD₆₇ mRNA-expressing neurons was decreased in the superficial layers of the deafferented horn, while GABA immunostaining of axonal fibres located in this region was highly increased. Seven days after lesion, on the other hand, many GAD₆₇ mRNA-expressing neurons were bilaterally detected in deep dorsal and ventral layers, this expression being correlated with the increased detection of GADs₆₇ immunostained somata and with the reduction of GABA immunostaining of axons. GABA immunostaining was frequently found to be associated with reactive astrocytes that exhibited intense immunostaining for glial fibrillary acidic protein (GFAP) but remained GADs₆₇ negative. These results indicate that degeneration of afferent terminals induces a biphasic response of GABAergic spinal neurons located in the dorsal horn and show that many spinal neurons located in deeper regions re-express GAD₆₇, suggesting a possible participation of the local GABAergic system in the reorganization of disturbed spinal networks.     

Distribution of glutamic acid decarbocylase and gamma-aminobutyric acid in thehypoglossal nucleus in the rat

Immunocytochemistry was used to investigate the distribution of glutamic acid decarboxylase (GAD) and gamma-aminobutyric acid (GABA) in the hupoglossal nucleus (XII) of the adult rat. The distribution of GAD and GABA was found to be co-extensive throughout XII. Although immunoreactivity was moderately dense in all regions, the intensity of staining was greatest in the ventral district of XII particularly ventromedially in the caudal half of the nucleus. Immunoreactive terminal-like profiles were observed around motoneuron somata and dendrites. There also was evidence of sparse mediolaterally-oriented densities of immunoreactivety at the junction of XII and the dorsal vagal nucleus and between dorsal and ventral districts of XII. In addition, neurons staining positive for GABA were found scattered within XII laterally and immediately outside of XII in and around the nucleus of Roller. These observations suggest a complex, differential distribution of GABA in XII and are discussed in relation to tongue motor behavior.     

Ultrastructure of synaptic remodeling in piriform cortex of adult rats after neonatal olfactory bulb removal: an immunocytochemical study

The purpose of this investigation was to study possible remodeling in synaptic structures of the piriform cortex (PC) of adult rats following neonatal deafferentation by removal of the olfactory bulb (OB) at birth. Emphasis was placed on possible qualitative changes in the ultrastructure and immunocytochemical localization of cholecystokinin (CCK, a possible excitatory neurotransmitter or modulator) and glutamic acid decarboxylase (GAD, precursor enzyme to the inhibitory transmitter GABA) in axons, terminals, and synaptic complexes. Light microscopic results in normal adult material show that GAD-positive terminals form a dense band subjacent to the lateral olfactory tract (LOT), become less dense in deeper Ib, and are rare in layer II. Following deafferentation, GAD-positive terminals appear denser and more homogeneously distributed throughout layer I and are also more prevalent in layer II. Ultrastructural results of normals and controls indicate GAD-positive terminals normally contain pleomorphic or flattened vesicles and form symmetric contacts onto dendritic shafts and branches throughout layer I. In deafferented layer I not only do there appear to be greater numbers of symmetric GAD-positive contacts, but in contrast to normals, asymmetric contacts mainly onto spines are now present. Light microscopic results from deafferented material also show an apparent proliferation with spread or sprouting of CCK-positive fibers or axonlike structures mainly into layer Ia, whereas these fibers are normally observed only in the LOT and are generally few in number. Also in normals the few CCK-positive terminals in the area subjacent to the LOT contain flattened or pleomorphic vesicles and form symmetric contacts. Deafferentation results in CCK-positive terminals throughout layer I with a greater frequency of synaptic contacts which now also include a few asymmetric contacts onto spines. The findings clearly show modifications in synaptic patterns of immunocytochemical-labeled terminals that might be compatible with the process of atypical reinnervation of deafferented postsynaptic sites and possible ingrowth of new axons.     

The effect of the convulsant allylglycine (2-amino-4-pentenoic acid) on the activity of glutamic acid decarboxylase and the concentration of GABA in different regions of guinea pig brain

Intraperitoneal administration of allylglycine to guinea pigs resulted in convulsions approximately 3 hr later. The concentration of GABA and the activity of GAD were significantly reduced in three brain areas, namely the cochlear nucleus, inferior colliculus and cerebral cortex, with the smallest changes being observed in the cortex. There were large in vitro regional variations in the extent of the allylglycine inhibition in brain areas from guinea pig, cat and rat, with those areas rich in GAD activity being least affected. Endogenous GAD activities in the brain regions were found to be inversely correlated with the percentage allylglycine inhibition (P < 0.005). Other inhibitors of GAD activity i.e. NaCl, Zn²⁺ and thiosemicarbazide showed no such regional variation of inhibition. The results suggest that the regional differences in allylglycine inhibition reflect anomalies of the metabolism of the drug per se, and probably do not indicate regional differences in GABA turnover and metabolism.     

文拉法辛缓释片治疗广泛性焦虑障碍对照研究

目的 探讨文拉法辛缓释片治疗广泛性焦虑障碍的临床效果和社会功能康复状况.方法 将75例广泛性焦虑障碍患者随机分为两组,研究组38例,口服文拉法辛缓释片治疗,对照组37例,口服劳拉西泮治疗,观察8周.于治疗前及治疗1周、2周、4周、8周末采用汉密顿焦虑量表、社会功能缺陷筛选量表、副反应量表评定临床疗效和不良反应.结果 治疗后两组汉密顿焦虑量表、社会功能缺陷筛选量表总分均较治疗前有显著下降(P＜0.01);治疗1周、2周末对照组汉密顿焦虑量表评分较研究组下降更显著(P＜0.01);治疗4周、8周末,研究组汉密顿焦虑量表、社会功能缺陷筛选量表评分较对照组下降更显著(P＜0.01).治疗8周末研究组有效率92.11%,对照组为89.19%,两组差异无显著性(P＞0.05).研究组不良反应发生率为23.63%,对照组为64.85%,研究组显著低于对照组(χ2=12.902,P＜0.01).结论文拉法辛治疗广泛性焦虑障碍中远期疗效优于劳拉西泮,安全性高,依从性好,改善社会功能效果显著,可作为治疗广泛性焦虑障碍的一线药物在临床推广应用.     

Therapy with GAD in diabetes

The enzyme glutamic acid decarboxylase (GAD) is of great importance for the neurotransmission in the central nervous system, and therefore of interest for treatment of pain and neurological disease. However, it is also released in pancreas although its role is not quite clear. GAD is a major auto‐antigen in the process leading to type 1 diabetes with both a clear cell‐mediated immune response to GAD and auto‐antibodies to GAD (GADA), which can be used as a predictor of diabetes. Administration of the isoform GAD65 can prevent autoimmune destruction of pancreatic beta cells in non‐obese diabetic (NOD) mice and the subsequent need for exogenous insulin replacement. In Phase I and II studies an alum‐formulated vaccine (Diamyd) has shown to be safe, and in a dose‐finding study in Latent Autoimmune Diabetes in Adults (LADA) patients 20‐µg was given subcutaneously one month apart indicating preservation of residual insulin secretion. A double‐blind randomized Phase II trial in 70 patients (10–18 years old) with recent‐onset type 1 diabetes showed significant preservation of residual insulin secretion and a GAD‐specific immune response, both humoral and cell‐mediated, but no treatment‐related adverse events. With this promising background further studies are on their way, both intervention in newly diagnosed type 1 diabetic patients, and trials to prevent the disease. Copyright © 2009 John Wiley & Sons, Ltd.     

Age-related changes in GAD levels in the central auditory system of the rat

Changes in the levels of gamma-aminobutyric acid (GABA) are known to occur in different parts of the brain during aging. In our study we attempted to define the effect that aging has on glutamate decarboxylase (GAD), the key enzyme in the synthesis of GABA, in the central parts of the auditory system. Age-related changes in GAD65 and GAD67 levels were investigated using immunohistochemistry and Western blotting in the inferior colliculus (IC), the auditory cortex (AC) and the visual cortex in Long-Evans rats. The results show that aging is associated with a decrease in the numbers of GAD65- and 67-immunoreactive neurons and the optical density of their somas in both the IC and AC. Western blot analysis revealed a pronounced age-related decline in the levels of GAD65 and 67 proteins in both the IC and AC. For comparison, in the visual cortex the decrease in both proteins was less pronounced than in the IC and AC. A similar pattern of age-related changes was found in Fischer 344 rats, a strain that manifests a rapid loss of hearing function with aging. The observed age-related decline in the levels of GAD65 and 67 may contribute significantly to the deterioration of hearing function that accompanies aging in mammals, including man.