ergoline and preproenkephalin

Studies in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys and in parkinsonian patients show elevated preproenkephalin (PPE) mRNA levels, unaltered by chronic L-DOPA therapy, whereas preprotachykinin (PPT) mRNA levels are decreased by the lesion and corrected by L-DOPA. The relative contributions of the dopamine D1 and D2 receptors for PPE mRNA regulation were investigated in the present study and compared with those for PPT mRNA. In situ hybridization was used to measure peptide mRNA levels in the striatum of MPTP cynomolgus monkeys after chronic 1-month treatment with the D1 agonist SKF-82958, administered subcutaneously in pulsatile or continuous mode, compared with the long-acting D2 agonist cabergoline. Normal as well as untreated MPTP animals were also studied. PPE mRNA levels were elevated in the caudate nucleus and putamen of untreated MPTP monkeys compared with control animals with a more pronounced increase in the lateral as compared with the medial part of both structures. PPT mRNA levels showed a rostrocaudal gradient, with higher values in the middle of the caudate-putamen and more so in the medial versus the lateral parts. PPT mRNA levels were decreased in the caudate and putamen of untreated MPTP monkeys compared with control animals, and this was observed in the middle and posterior parts of these brain areas. Elevated PPE and decreased PPT mRNA levels observed after MPTP exposure were corrected after treatment with cabergoline (0.25 mg/kg, every other day), a dose that had antiparkinsonian effects and did not give sustained dyskinesia. In contrast, elevated PPE mRNA levels observed in untreated MPTP monkeys were markedly increased by pulsatile administration of SKF-82958 (1 mg/kg, three times daily) in two monkeys in which the parkinsonian symptoms were improved and dyskinesias developed, whereas it remained close to control values in a third one that did not display dyskinesias despite a sustained improvement in disability; a shorter duration of motor benefit (wearing off) over time was observed in these three animals. By contrast, pulsatile administration of SKF-82958 corrected the decreased PPT level observed in untreated MPTP monkeys. Continuous treatment with SKF-82958 (equivalent daily dose) produced no clear antiparkinsonian and dyskinetic responses and did not alter the denervation-induced elevation of PPE or decrease of PPT mRNA levels. The present data suggest an opposite contribution of the dopamine D1 rece

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Animals; Behavior, Animal; Benzazepines; Brain Chemistry; Cabergoline; Corpus Striatum; Denervation; Dopamine Agents; Dopamine Agonists; Enkephalins; Ergolines; Female; Gene Expression; Macaca fascicularis; Movement Disorders; Protein Precursors; Pulsatile Flow; Receptors, Dopamine D1; Receptors, Dopamine D2; RNA, Messenger; Tachykinins

The effect of administration of subtype selective dopamine (DA) agonists on the 6-hydroxydopamine (6-OHDA) lesion-induced increase of striatal preproenkephalin (PPE) mRNA was examined by dot-blot hybridization. Eight days following a unilateral 6-OHDA lesion of the substantia nigra pars compacta (SNc), PPE mRNA levels in the ipsilateral striatum were increased approximately two-fold. Administration of the D2 DA agonist, quinpirole, dose-dependently attenuated the 6-OHDA lesion-induced increase in striatal PPE mRNA. The effect of quinpirole was blocked by coadministration of the D2 DA antagonist eticlopride. In contrast, administration of the D1 DA agonist, SKF 38393, either dose-dependently augmented or had no effect on the 6-OHDA lesion-induced increase in striatal PPE mRNA. In the contralateral striatum, administration of quinpirole decreased PPE mRNA, while administration of SKF 38393 increased PPE mRNA compared to sham lesioned control levels. These data suggest the action of DA at D1 and D2 DA receptors differentially regulates striatal PPE mRNA levels and the apparent inhibition of ENK biosynthesis by DA is mediated via an interaction with D2 DA receptors.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Blotting, Northern; Corpus Striatum; Desipramine; Dopamine; Enkephalins; Ergolines; Gene Expression Regulation; Kinetics; Male; Nucleic Acid Hybridization; Oligonucleotide Probes; Oxidopamine; Protein Precursors; Quinpirole; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Dopamine D1; Receptors, Dopamine D2; Reference Values; RNA, Messenger; Salicylamides; Stereotaxic Techniques

Electrical stimulation of the medial forebrain bundle, in a manner that augmented the release of dopamine in the forebrain, rapidly increased the striatal content of preproenkephalin (but not preprotachykinin) mRNA. This effect was mimicked by administration of either the indirect (dopamine-releasing) agonist methamphetamine or by the D-2 dopamine receptor agonist quinpirole, but not by the D-1 agonist SKF 38393. These data suggest that D-2 receptors, which mediate a stimulatory effect on enkephalin gene expression, may be subsaturated under basal conditions and, therefore, responsive to increases in synaptic dopamine.

Topics: Animals; Corpus Striatum; Diencephalon; Dopamine; Electric Stimulation; Enkephalins; Ergolines; Male; Medial Forebrain Bundle; Methamphetamine; Neural Pathways; Protein Precursors; Quinpirole; Rats; Rats, Inbred Strains; Receptors, Dopamine; Receptors, Dopamine D2; RNA, Messenger; Telencephalon

The present investigation examined the effects of neonatal and adult 6-hydroxydopamine (6-OHDA)-induced lesions of dopaminergic neurons on opioid and tachykinin peptides and their gene expression in the rat basal ganglia. This work was undertaken to determine if changes in these neuropeptide systems were contributing to the differing behavioral responses observed between neonatally and adult-lesioned rats after dopamine agonist administration. [Met5]Enkephalin (ME) content was increased in striatal tissue from both 6-OHDA-lesioned groups when compared with unlesioned controls. Dynorphin-A (1-8) content was not altered by the 6-OHDA lesions. The tachykinin peptides substance P and neurokinin A were significantly decreased in level in the striatum and substantia nigra of neonatally lesioned rats, but not in the adult-lesioned rats, when compared with unlesioned controls. Proenkephalin mRNA abundance (quantified by an RNA-cDNA hybridization technique) and precursor level (as reflected by cryptic ME content) were increased in the striatum of both neonatally and adult-lesioned rats. The abundance of preprotachykinin mRNA coding for the tachykinin peptides was markedly decreased in the neonatally lesioned rats, whereas only a small reduction was observed in the adult-lesioned rats. These results suggest that destruction of dopamine-containing terminals with 6-OHDA elevates the level of ME by accelerating transcriptional and/or translational processes; conversely, the reduced content of tachykinins in neonatally lesioned rats may be due to a reduction in such processes. Thus, preproenkephalin-A and preprotachykinin gene expression are differentially regulated after lesioning of catecholamine-containing neurons, an observation suggesting a close functional relationship among these neurotransmitter systems. Furthermore, of the peptides studied, only levels of the tachykinin peptides were differentially altered in the striatum and substantia nigra of the neonatally lesioned rats compared with adult-lesioned rats; therefore, these peptides may be associated with the distinctive behavioral differences between neonatally and adult 6-OHDA-lesioned rats given dopamine agonists.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Aging; Animals; Animals, Newborn; Benzazepines; Corpus Striatum; Dopamine; Dynorphins; Enkephalin, Methionine; Enkephalins; Ergolines; Female; Gene Expression Regulation; Hippocampus; Hydroxydopamines; Male; Motor Activity; Neuropeptides; Oxidopamine; Peptide Fragments; Protein Precursors; Quinpirole; Rats; Rats, Inbred Strains; RNA, Messenger; Substantia Nigra; Tachykinins