Basal ganglia neuronal nitric oxide synthase mRNA expression in Parkinson's disease

Expression of nitric oxide synthase (NOS) mRNA in post mortem brain was studied in putamen, globus pallidus and subthalamic nucleus (STN) of neurologically normal control subjects and patients with Parkinson's disease (PD) using in situ hybridization histochemistry. In PD, a significant increase in NOS mRNA expression was observed in the dorsal two-thirds of the STN with respect to the ventral one-third of the STN. A significant increase in NOS mRNA expression per cell in the medial medullary lamina of the globus pallidus was also observed in PD. NOS mRNA expression was significantly reduced in PD putamen. These findings provide evidence of increased activity of STN neurotransmitter systems in PD and demonstrate for the first time in any species that basal ganglia nitric oxide systems can be selectively regulated in response to changes in dopaminergic input.

Selective increase in somatostatin mRNA expression in human basal ganglia in Parkinson's disease

Levels of the neurotransmitter somatostatin (SS) have previously been shown to be reduced in the cortex and hippocampus of demented parkinsonian patients and patients with Alzheimer's disease. In situ hybridisation histochemistry (ISHH) was performed with an 35S tail-labelled oligonucleotide DNA probe to human SS mRNA, to examine its expression within the striatum, medial medullary lamina (MML) and reticular thalamic nucleus in Parkinson's disease (PD) and in matched controls. A chronic unilaterally MPTP-lesioned L-DOPA-naive primate model was also examined for comparison of SS mRNA expression with that in human L-DOPA treated PD subjects. Quantitation of SS mRNA expression on emulsion dipped sections revealed a significant increase (82%) in the MML of the globus pallidus in PD (56.5 microm2 of silver grain/cell, n = 9 cases) compared to controls (26.3 microm2/cell, n = 13 cases, p < 0.01, Student's t-test), paralleling the increase previously observed by this group for NOS mRNA. SS mRNA expression was higher in the dorsolateral than ventromedial putamen in controls (p < 0.001; DL: 24.89 +/- SEM 1.35; VM: 17.96 +/- SEM 2.63; n = 14) but this gradient was lost in PD cases (p > 0.05; DL: 22.68 +/- 1.94; VM: 22.17 +/- 2.94; n = 10). These findings suggest specific modification of basal ganglia SS-ergic pathways in PD.

Glutamate decarboxylase-67 messenger RNA expression in normal human basal ganglia and in Parkinson's disease

Expression of glutamate decarboxylase-67 messenger RNA was examined in the basal ganglia of normal controls and of cases of Parkinson's disease using in situ hybridization histochemistry in human post mortem material. In controls glutamate decarboxylase-67 messenger RNA expression was detected in all large neurons in both segments of the globus pallidus and in three neuronal subpopulations in the striatum as well as in substantia nigra reticulata neurons and in a small sub-population of subthalamic neurons. In Parkinson's disease, there was a statistically significant decrease of 50.7% in glutamate decarboxylase-67 messenger RNA expression per neuron in the lateral segment of the globus pallidus (controls: mean 72.8 microns2 +/- S.E.M. 8.7 of silver grain/neuron, n = 12; Parkinson's disease: mean 35.9 microns2 +/- S.E.M. 9.7 of silver grain/neuron, n = 9, P = 0.01, Student's t-test). In the medial segment of the globus pallidus, there was a small, but non-significant decrease of glutamate decarboxylase-67 messenger RNA expression in Parkinson's disease (controls: mean 100.6 microns2 +/- S.E.M. 7.2 of silver grain/neuron, n = 11; Parkinson's disease: mean 84.8 microns2 +/- S.E.M. 13.0 of silver grain/neuron, n = 7, P = 0.1, Student's t-test). No significant differences in glutamate decarboxylase-67 messenger RNA were detected in striatal neuronal sub-populations between Parkinson's disease cases and controls. These results are the first direct evidence in humans that there is increased inhibitory drive to the lateral segment of the globus pallidus in Parkinson's disease, as suggested by data from animal models. We therefore provide theoretical support for current experimental neurosurgical approaches to Parkinson's disease.

Preproenkephalin and preprotachykinin messenger RNA expression in normal human basal ganglia and in Parkinson's disease

Striatal expression of preproenkephalin and preprotachykinin messenger RNA was studied in normal controls and in patients with Parkinson's disease using in situ hybridization histochemistry. In controls, preproenkephalin messenger RNA was expressed in a population of medium-sized neurons of mean cross-sectional area 165 microns 2, accounting for 66% of striatal medium-sized neurons, whereas preprotachykinin messenger RNA was expressed in a population of medium-sized neurons of mean cross-sectional area 204 microns 2 (23% larger than those expressing enkephalin, P < 0.05), accounting for 58% of medium-sized striatal neurons. Much lower levels of both preproenkephalin messenger RNA and preprotachykinin messenger RNA were expressed by large neurons in the globus pallidus and substantia nigra reticulata. In addition, preproenkephalin messenger RNA was expressed at low levels by neurons in the subthalamic nucleus. In Parkinson's disease cases, there was a statistically significant increase in preproenkephalin messenger RNA expression in the body of the caudate (109% increase, P < 0.05) and in the intermediolateral putamen (55% increase, P < 0.05) due to an increase in the level of gene expression per neuron rather than an increase in the number of neurons expressing preproenkephalin messenger RNA. Similar increases were observed in other putaminal subregions and in the putamen as a whole, but these did not reach statistical significance. No change in preprotachykinin messenger RNA expression was detected. These findings demonstrate selective up-regulation of a striatal neuropeptide system in Parkinson's disease compatible with increased activity of the "indirect" striatopallidal pathway, which is thought to play a crucial role in the pathophysiology of akinesia and rigidity in this condition.

Tissue pH as an indicator of mRNA preservation in human post-mortem brain

The relationship between pH and mRNA preservation in post-mortem human brain was examined using in situ hybridization histochemistry and Northern hybridization with oligonucleotide probes in a large group of human subjects, including control and neuropathological cases. Tissue pH was found to correlate strongly with preservation of four mRNA species in three brain areas. Tissue with low pH, assumed to result from prolonged terminal hypoxia, contained reduced or absent mRNA, while tissue with higher pH was found to contain quantifiable amounts, the values for pathological brain samples being comparable to those for control material of similar pH. Measurement of tissue pH provides a simple means to screen post-mortem brain for mRNA preservation and is suggested as a means to match material in case-control studies of human neurodegenerative disease.