Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

GABA (gamma-amino-butyric acid) receptors are a family of proteins involved in the GABAergic neurotransmission of the mammalian central nervous system (CNS). They have physiological importance and clinical relevance in several diseases. We report the identification, cloning, and fine mapping of the human cDNA for GABAB receptor. A 4.2-Kb cDNA containing an open reading frame for a predicted protein of 960 aa was isolated from a fetal brain cDNA library. It had a strong identity (91.5%) with the rat GABAB receptor (rGB1A) nucleotide sequence, that corresponded to 98.6% identity at the amino acid level. Expression of the GABAB at the transcription level was detected by Northern analysis in all brain areas examined. The GABAB receptor has been mapped to human chromosome 6p21.3 within the HLA class I region close to the HLA-F gene. Susceptibility loci for multiple sclerosis, epilepsy, and schizophrenia have been suggested to map in this region.
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PMID:GABA (gamma-amino-butyric acid) neurotransmission: identification and fine mapping of the human GABAB receptor gene. 975 14

Dual probe microdialysis was employed in intact rat brain to investigate the effect of intrastriatal perfusion with selective dopamine D1 and D2 receptor agonists and with c-fos antisense oligonucleotide on (a) local GABA release in the striatum; (b) the internal segment of the globus pallidus and the substantia nigra pars reticulata, which is the output site of the strionigral GABA pathway; and (c) the external segment of the globus pallidus, which is the output site of the striopallidal GABA pathway. The data provide functional in vivo evidence for a selective dopamine D1 receptor-mediated activation of the direct strionigral GABA pathway and a selective dopamine D2 receptor inhibition of the indirect striopallidal GABA pathway and provides a neuronal substrate for parallel processing in the basal ganglia regulation of motor function. Taken together, these findings offer new therapeutic strategies for the treatment of dopamine-linked disorders such as Parkinson's disease, Huntington's disease, and schizophrenia.
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PMID:Functional neuroanatomy of the basal ganglia as studied by dual-probe microdialysis. 986 60

Here we have described a novel excitotoxic process in which hypofunctional NMDA receptors cease driving GABA ergic neurons which cease inhibiting excitatory transmitters in the brain. These disinhibited excitatory transmitters then act in concert to slowly hyperstimulate neurons in corticolimbic brain regions. We have discussed how such an abnormality could exist in the brains of individuals with schizophrenia or AD and could account for the clinical stigmata of the two disorders. In addition, we have highlighted how other disorder-specific factors would account for the differences in the clinical presentation of AD and schizophrenia. In an animal model, pharmacological methods have been developed for preventing the overstimulation of these vulnerable corticolimbic pyramidal neurons and at least some of these methods may be applicable for treating AD and schizophrenia.
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PMID:The glutamate synapse in neuropsychiatric disorders. Focus on schizophrenia and Alzheimer's disease. 993 93

Phencyclidine (PCP) is a drug of abuse that produces schizophrenia-like symptoms in humans and increases locomotor activity and stereotypic behavior in rodents. PCP-induced alteration in rat locomotor activity is thought to be mediated by an inhibition of N-methyl-D-aspartate (NMDA) receptors in the striatum and other brain regions. In this study, rats treated chronically with PCP (20 mg/kg once per day for 5 days) showed a marked increase in locomotor activity following a PCP challenge (3.2 mg/kg) administered after either 3 or 8 days of withdrawal. In biochemical assays, the release of striatal [14C]GABA by NMDA was enhanced by about 77% by chronic PCP treatment, whereas [3H]ACh release was increased by about 31% in tissue from PCP-treated rats. Even though binding experiments with 1-[1-(2-thiethyl)cyclohexyl]piperidyl-3,4 3H(N) ([3H]TCP) showed no alteration in the Kd or Bmax in whole striatum, quantitative immunocytochemical experiments found an upregulation in the NR1 subunit in the cell bodies and neuropil of cortical and striatal regions of the forebrain following chronic PCP treatment. An increase in the size of NR1-immunoreactive cells in the forebrain was also observed following chronic PCP treatment. Together, these data may help in understanding the mechanisms underlying the adaptive response to chronic reduction in glutamatergic NMDA transmission that has been postulated to be involved in the etiology of schizophrenia.
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PMID:Augmentation of locomotor activity by chronic phencyclidine is associated with an increase in striatal NMDA receptor function and an upregulation of the NR1 receptor subunit. 1002 41

Having shown a decrease in serotonin2A receptors in the dorsolateral prefrontal cortex (DLPFC) from schizophrenic subjects, we have now determined if this change was reflective of widespread changes in neurochemical markers in DLPFC in schizophrenia. In Brodmann's area (BA) 9 from 19 schizophrenic and 19 control subjects, we confirmed a decrease in the density of [3H]ketanserin binding to serotonin2A receptors in tissue from the schizophrenic subjects [39 +/- 3.3 vs. 60 +/- 3.6 fmol/mg estimated tissue equivalents (ETE); p < 0.005]. In addition, the density of [3H]muscimol binding to GABA(A) receptors was increased in the schizophrenic subjects (526 +/- 19 vs. 444 +/- 28 fmol/mg ETE; p < 0.02). [3H]YM-09151-2, N-[1-(2-thienyl)cyclohexyl]-3,4-[3H]piperidine, [3H]SCH 23390, [3H]mazindol, and N(G)-nitro-L-[3H]arginine binding to BA 9 did not differ between groups, and there was no specific binding of [3H]raclopride or 7-hydroxy-2-(di-n-[3H]propylamino)tetralin to BA 9 from either cohort of subjects. This suggests the density of dopamine D1-like and NMDA receptors, the dopamine transporter, and nitric oxide synthase activity are not altered in BA 9 from schizophrenic subjects. The selective nature of the changes in serotonin2A and GABA(A) receptors in DLPFC could indicate that these changes are involved in the pathology of schizophrenia.
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PMID:Changes in serotonin2A and GABA(A) receptors in schizophrenia: studies on the human dorsolateral prefrontal cortex. 1009 66

Despite a hundred years' research, the neuropathology of schizophrenia remains obscure. However, neither can the null hypothesis be sustained--that it is a 'functional' psychosis, a disorder with no structural basis. A number of abnormalities have been identified and confirmed by meta-analysis, including ventricular enlargement and decreased cerebral (cortical and hippocampal) volume. These are characteristic of schizophrenia as a whole, rather than being restricted to a subtype, and are present in first-episode, unmedicated patients. There is considerable evidence for preferential involvement of the temporal lobe and moderate evidence for an alteration in normal cerebral asymmetries. There are several candidates for the histological and molecular correlates of the macroscopic features. The probable proximal explanation for decreased cortical volume is reduced neuropil and neuronal size, rather than a loss of neurons. These morphometric changes are in turn suggestive of alterations in synaptic, dendritic and axonal organization, a view supported by immunocytochemical and ultrastructural findings. Pathology in subcortical structures is not well established, apart from dorsal thalamic nuclei, which are smaller and contain fewer neurons. Other cytoarchitectural features of schizophrenia which are often discussed, notably entorhinal cortex heterotopias and hippocampal neuronal disarray, remain to be confirmed. The phenotype of the affected neuronal and synaptic populations is uncertain. A case can be made for impairment of hippocampal and corticocortical excitatory pathways, but in general the relationship between neurochemical findings (which centre upon dopamine, 5-hydroxytryptamine, glutamate and GABA systems) and the neuropathology of schizophrenia is unclear. Gliosis is not an intrinsic feature; its absence supports, but does not prove, the prevailing hypothesis that schizophrenia is a disorder of prenatal neurodevelopment. The cognitive impairment which frequently accompanies schizophrenia is not due to Alzheimer's disease or any other recognized neurodegenerative disorder. Its basis is unknown. Functional imaging data indicate that the pathophysiology of schizophrenia reflects aberrant activity in, and integration of, the components of distributed circuits involving the prefrontal cortex, hippocampus and certain subcortical structures. It is hypothesized that the neuropathological features represent the anatomical substrate of these functional abnormalities in neural connectivity. Investigation of this proposal is a goal of current neuropathological studies, which must also seek (i) to establish which of the recent histological findings are robust and cardinal, and (ii) to define the relationship of the pathological phenotype with the clinical syndrome, its neurochemistry and its pathogenesis.
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PMID:The neuropathology of schizophrenia. A critical review of the data and their interpretation. 1021 75

The present study examined the effects of local microinjections of the GABA chloride channel blocker Picrotoxin into the superior colliculus (SC) on prepulse inhibition (PPI) of the acoustic startle response (ASR) in rats. PPI is a useful model for the investigation of the neuronal basis of sensorimotor gating which is deficient in some psychiatric disorders, such as schizophrenia. Blockade of GABA activity within the SC by Picrotoxin injections (leading to a moderate stimulation of the SC) significantly enhanced PPI without affecting the ASR baseline amplitude or the spontaneous motor activity. Based on these results we discuss the role of the SC in a hypothetical neuronal circuit mediating PPI of the ASR.
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PMID:Enhancement of prepulse inhibition after blockade of GABA activity within the superior colliculus. 1037 79

Repeated administration of amphetamine or methamphetamine (MA) results in an augmentation of its locomotor-activating effects, which is a phenomenon known as behavioral sensitization. In humans, chronic use of the drug elicits a progressive augmentation in paranoid symptoms that closely resemble schizophrenia. Behavioral sensitization has some common properties with other forms of neural plasticity such as kindling, learning and long-term potentiation (LTP). The author examined in the present study whether behavioral sensitization could be blocked by GABA-benzodiazepine agonists, known to inhibit kindling, learning as well as LTP. Rats (Male Wistar-King rats) treated with MA (1 mg/kg, s.c.) for 10 days displayed significantly enhanced motor activity when tested with MA (1 mg/kg) after a 7-8 day withdrawal period indicating the acquisition of behavioral sensitization. Treatment with clonazepam (CZP) (0.5 and 2.0 mg/kg), a GABA-benzodiazepine agonist, prior to MA administration prevented the acquisition of sensitization. In contrast, treatment with flumazenil (Flu) (10 mg/kg), a GABA-benzodiazepine antagonist, prior to MA administration did not affect the acquisition of sensitization. And treatment with Flu prior to CZP administration suppressed the inhibitory effect of CZP. CZP had no effect on the expression of sensitization in the sensitized rats, when given prior to the MA readministration. These results suggest that stimulation of GABA-benzodiazepine receptors plays a role in the acquisition but not in the expression of behavioral sensitization.
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PMID:The role of gamma-aminobutyric acid (GABA)-benzodiazepine neurotransmission in an animal model of methamphetamine-induced psychosis. 1038 62

The medial septum, diagonal bands, ventral pallidum, substantia innominata, globus pallidus, and internal capsule contain a heterogeneous population of neurons, including cholinergic and noncholinergic (mostly GABA containing), corticopetal projection neurons, and interneurons. This highly complex brain region, which constitutes a significant part of the basal forebrain has been implicated in attention, motivation, learning, as well as in a number of neuropsychiatric disorders, such as Alzheimer's disease, Parkinson's disease, and schizophrenia. Part of the difficulty in understanding the functions of the basal forebrain, as well as the aberrant information-processing characteristics of these disease states lies in the fact that the organizational principles of this brain area remained largely elusive. On the basis of new anatomical data, it is proposed that a large part of the basal forebrain corticopetal system be organized into longitudinal bands. Considering the topographic organization of cortical afferents to different divisions of the prefrontal cortex and a similar topographic projection of these prefrontal areas to basal forebrain regions, it is suggested that several functionally segregated cortico-prefronto-basal forebrain-cortical circuits exist. It is envisaged that such specific "triangular" circuits could amplify selective attentional processing in posterior sensory cortical areas.
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PMID:The basal forebrain corticopetal system revisited. 1041 58

Propagation and prolongation of rapid neuronal discharge underlies the epilepsies. However, episodic focal rapid neuronal discharges limited to discrete nuclei and pathways of the amygdala-hippocampal-septal-hypothalamic networks are the language of physiologic message systems for endocrine regulation and reproductive activities vital to the survival of the organism and the species. To prevent prolongation and propagation of physiologic pulsed excitation to areas outside specific networks and resultant epileptic seizures, these discharges must be limited in extent and time by powerful inhibitory processes. The nucleus accumbens, a unit of the extended amygdala, and the monoamines and GABA are components of the inhibitory networks that restrict physiologic rapid discharge in duration and in location. In parallel to the relationship of excessive neuronal excitation to epilepsy, evidence will be presented that excessive inhibition via one or more components of these inhibitory networks or diminished excitation underlies development of some psychoses, including schizophrenia.
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PMID:Epilepsy, schizophrenia, and the extended amygdala. 1041 70


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