[Show abstract][Hide abstract] ABSTRACT: Sensory-processing dysfunctions, deficit states, and the combinations of seemingly disparate behavioral symptoms of schizophrenia are addressed with regard to a common thread--the possibility of dysfunctional processing in the thalamus. Recent views of the connectional neuroanatomy and electrical activity of thalamus are examined. A hypothesis is presented in which disturbances in the timing and phasic neuronal activity of the thalamus and, especially, its connections with other brain regions may result in many of the behavioral manifestations of schizophrenia. It is suggested that neurotransmitter or other chemical imbalances might produce such thalamic disturbances. Experimental findings of enhanced dopamine content in the thalami of schizophrenic patients are reported. Several varieties of distributional patterns of this elevated dopamine are shown and evaluated.
[Show abstract][Hide abstract] ABSTRACT: We kinetically characterized D2 receptors in thalami pooled from a group of Sprague-Dawley rats and then determined thalamic levels of dopamine (DA), homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), and norepinephrine (NE) in relation to a measure of thalamic DA D2 receptor densities in another group of rats. The equilibrium dissociation constant (kd) was estimated as 0.1 nM by three independent methods, while the Bmax for thalamic D2 receptors was found to be 6.4 fmol/mg p using 3H-spiperone as ligand and ketanserin to occlude 5HT2 binding. Kinetic constants were in agreement with previously reported kinetic data from rodent caudate-putamen. This suggests that thalamic D2 receptors are similar to D2 receptors from other brain areas. Mean thalamic levels of DA (22.6 ng/mg p), DOPAC (1.19 ng/mg p) and HVA (0.31 ng/mg p) concur with previous reports of a sparse distribution of thalamic DA neurons. D2 receptor densities were positively correlated with DA metabolites DOPAC (P less than .05; r = 0.423) and HVA (P less than .05; r = 0.368), but not DA or NE. These results establish fundamental characteristics of thalamic DA neurotransmission to assist in the investigation of behavioral pharmacology of this area.
Life Sciences 02/1991; 48(19):1845-52. DOI:10.1016/0024-3205(91)90240-C · 2.70 Impact Factor
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