phosphorus-radioisotopes and preproenkephalin

Topics: Animals; Brain; Enkephalins; Gene Expression; In Situ Hybridization; Male; Molecular Probes; Phosphorus Radioisotopes; Protein Precursors; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D2; Reference Standards; RNA, Messenger; Sulfur Radioisotopes

The striatum is vulnerable to hypoxic-ischemic injury during development. In a rodent model of perinatal hypoxia-ischemia, it has been shown that striatal neurons are not uniformly vulnerable. Cholinergic neurons and NADPH-diaphorase-positive neurons are relatively spared. However, it is unknown what classes of striatal neurons are relatively sensitive. One of the major classes of striatal neurons uses enkephalin as a neurotransmitter. We have studied the effect of early hypoxic-ischemic injury on this class of neurons using a quantitative solution hybridization assay for preproenkephalin mRNA in conjunction with in situ hybridization. Hypoxia-ischemia results in an early (up to 24 h) decrease in striatal preproenkephalin mRNA, which is shown by in situ hybridization to occur mainly in the dorsal portion of the striatum. By 14 days, whole striatal preproenkephalin mRNA and total enkephalin-containing peptide levels are normal. However, at 14 days, in situ hybridization reveals that regions of complete preproenkephalin mRNA-positive neuron loss remain in the dorsal region. Normal whole striatal levels are due to an up-regulation of preproenkephalin mRNA expression in the ventrolateral region of the injured striatum. Given the important role that the enkephalin-containing striatal efferent projection plays in regulating motor function, its relative loss may be important in the chronic disturbances of motor control observed in brain injury due to developmental hypoxic-ischemic injury.

Topics: Aging; Animals; Autoradiography; Brain Ischemia; Corpus Striatum; Enkephalins; Female; Hypoxia, Brain; In Situ Hybridization; NADPH Dehydrogenase; Neurons; Phosphorus Radioisotopes; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Suppression, Genetic

Unilateral 6-hydroxydopamine (6-OHDA)-induced lesion of the nigrostriatal dopamine (DA) pathway causes a significant increase of preproenkephalin (PPE) messenger RNA (mRNA) levels in the DA-depleted striatum in rat brain. Using an in situ hybridization (ISH) technique and computer-assisted microdensitometry, we quantified the changes in PPE mRNA levels in the striatum. Seven months after lesion, levels of PPE mRNA were 75% higher in the DA-depleted striatum than in the contralateral control striatum of the same animal or in the striatum of sham control animals. The implantation of embryonic dopaminergic neurons into the denervated striatum led to a complete reversal of this increase and, in grafted animals, levels of PPE mRNA were at control values. Moreover, this reversal extended beyond the areas reinnervated by the grafted dopaminergic neurons.

Topics: Animals; Autoradiography; Binding Sites; Brain Tissue Transplantation; Corpus Striatum; Enkephalins; Fetal Tissue Transplantation; In Situ Hybridization; Male; Oxidopamine; Phosphorus Radioisotopes; Piperazines; Protein Precursors; Rats; Rats, Wistar; Reference Values; RNA, Messenger; Substantia Nigra; Time Factors; Tritium

The effect of administration of the muscarinic antagonist scopolamine on the increase in striatal preproenkephalin (PPE) mRNA following a 6-hydroxydopamine (6-OHDA) lesion or chronic D2 dopamine (DA) antagonist treatment was examined by dot-blot hybridization. Administration of scopolamine dose-dependently attenuated the 6-OHDA lesion-induced increase in striatal PPE mRNA. Administration of the D2 DA antagonist eticlopride to naive rats increased striatal PPE mRNA in a dose- and time-dependent fashion. Chronic coadministration of scopolamine attenuated the eticlopride-induced increase in striatal PPE mRNA. Chronic administration of scopolamine alone did not alter striatal PPE mRNA levels. In contrast, chronic administration of eticlopride, scopolamine or the two combined decreased striatal preprotachykinin (PPT) mRNA to the same extent, suggesting that there was no direct interaction between D2 dopaminergic and cholinergic mechanisms in the regulation of striatal PPT mRNA. These data indicate that DA differentially regulates striatal PPE and PPT mRNA and suggest that dopaminergic regulation of striatal PPE mRNA is mediated in part through D2 DA effects on striatal cholinergic neurons.

Topics: Acetylcholine; Animals; Blotting, Northern; Corpus Striatum; Dose-Response Relationship, Drug; Enkephalins; Interneurons; Kinetics; Male; Models, Neurological; Nucleic Acid Hybridization; Oligonucleotide Probes; Oxidopamine; Phosphorus Radioisotopes; Protein Precursors; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Dopamine D2; RNA, Messenger; Salicylamides; Scopolamine