Long-term treatment of male F344 rats with deprenyl: assessment of effects on longevity, behavior, and brain function.

L-Deprenyl (selegiline) was chronically administered to male Fischer 344 rats via their drinking water beginning at 54 weeks of age (estimated daily dose: 0.5 mg/kg/day). Beginning at 84 weeks of age, the rats were behaviorally evaluated using a sensorimotor battery, a motor-learning task, and the Morris water maze. At 118 weeks of age, cerebellar noradrenergic function was evaluated in the surviving rats using in vivo electrochemistry. The rats were then sacrificed to measure brain monoamine oxidase activity and perform quantitative autoradiography to evaluate the effect of chronic deprenyl treatment on beta-adrenergic receptors in the cerebellum, alpha 2-adrenergic receptors several brain regions, and D1 and D2 dopamine receptors in the striatum. Deprenyl treatment reduced brain monoamine oxidase B activity by 85%, but had no effect on brain monoamine oxidase A. A clear effect of chronic deprenyl treatment upon longevity was not observed. Several measures of CNS function were altered in the deprenyl-treated animals: 1) spatial learning in the Morris water maze was improved; 2) electrochemical signals recorded following local application of NE were reduced, and the responsiveness to the reuptake blocker nomifensine was enhanced, in the cerebellum; 3) beta-adrenergic receptor binding affinity was increased in the cerebellum; 4) alpha 2-adrenergic receptor density was increased in the inferior colliculus; and 5) striatal D1 dopamine receptor density was reduced but binding affinity was enhanced. In contrast, chronic deprenyl treatment did not cause changes in: 1) sensorimotor function, as evaluated by balance beam, inclined screen, or wire hang tasks; 2) motor learning; 3) alpha 2-adrenergic receptor density in any region examined except for the inferior colliculus, or binding affinity in any region examined; or 4) striatal D2 dopamine receptor number or affinity. Thus, long-term oral administration of deprenyl extended the functional life span of rats with respect to cognitive, but not motor, performance.

Evidence for a defect in NADH: ubiquinone oxidoreductase (complex I) in Huntington's disease.

We evaluated electron transport chain activity in platelet mitochondria taken from HD patients. All 5 patients studied had striking depressions of NADH:ubiquinone oxidoreductase activity (complex I) (5.36 +/- 2.91 nmol/min/mg; control mean, 19.12 +/- 5.64 nmol/min/mg). Other electron transport chain activities were not significantly different from control values. HD may be caused by a mutation in 1 of the nuclear coded subunits of NADH:ubiquinone oxidoreductase.

Conditioned apomorphine-induced turning in 6-OHDA-lesioned rats.

Apomorphine-induced turning has been used to evaluate the extent of unilateral nigrostriatal denervation after 6-hydroxydopamine (6-OHDA) lesions and subsequent functional striatal reinnervation by catecholaminergic grafts. It has been noted that the pregraft rotational pattern is usually double peaked and that fetal ventral mesencephalic grafts or dopaminergic drugs will alter the second peak but leave the first relatively unchanged. We hypothesized that the first peak may be the result of factors extrinsic to the nigrostriatal dopamine system, specifically a conditioned turning response, and would, therefore, be unperturbed by the above treatments which increase dopaminergic (DA) inputs. This was investigated by injecting 6-OHDA, unilaterally, into the nigrostriatal pathway of several groups of young Fisher 344 rats. One experimental group was repeatedly tested with 0.05 mg/kg apomorphine and the rotations quantified. A second group received similar injections of apomorphine but were prevented from rotating. Vehicle control animals were also studied for both of the above experimental groups. Subsequent to the above treatment, all animals were tested unrestrained repeatedly on apomorphine. Our results support the conditioned response hypothesis in that the first peak is not present with the initial unrestrained apomorphine behavioral trial but is present upon the second and subsequent unrestrained trials. Moreover, the restrained but apomorphine-injected rats, as well as the control animals, manifest no first peak upon their first freely moving apomorphine test; the second and subsequent unrestrained apomorphine trials, in these groups, do manifest a first peak.(ABSTRACT TRUNCATED AT 250 WORDS)

D1 and D2 dopamine receptors in perinatal and adult basal ganglia.

There is reason to believe that dopamine is important in developmental programs of the basal ganglia, brain nuclei implicated in motor and cognitive processing. Dopamine exerts effects through dopamine receptors, which are predominantly of the D1 and D2 subtypes in the basal ganglia. Cocaine acts as a stimulant of dopamine receptors and may cause long-term abnormalities in children exposed in utero. Dopamine receptor (primarily D1) stimulation has been linked to gene regulation. Therefore, D1 and D2 receptor densities in perinatal and adult striatum and globus pallidus were examined using quantitative autoradiography. The most striking finding was that pallidal D1 receptor densities were 7-15 times greater in the perinatal cases than in the adult. Pallidal D2 receptor densities were similar at both ages. In both the adult and perinatal striatum, D2 receptor densities were greater in the putamen than in the caudate, and both D1 and D2 receptor densities were modestly enriched in caudate striosomes compared with the matrix. In both caudate and putamen, perinatal D1 receptor levels were within the adult range, whereas D2 receptor levels were only 50% of adult values. The development of D1 and D2 receptors appears to vary across the major subdivisions of the human basal ganglia. The facts that we found such extremely high levels of D1 receptors in the perinatal pallidum, and that D1 receptor activation influences gene regulation, suggest that the globus pallidus could be particularly susceptible to long-term changes with perinatal exposure to cocaine and other D1 receptor agonists or antagonists.

Net production of cerebrospinal fluid is decreased by SCH-23390.

A high density of binding sites for the ligands 3H-SCH-23390 and 3H-SKF-83566 has been found in the choroid plexus. Although these sites have similar pharmacology to D1 dopamine receptors, the high-affinity component of 3H-SCH-23390 binding in the choroid plexus has been identified as the 5-HT1c subtype of serotonin receptor. We investigated the possible role of these receptors in modulating the production of cerebrospinal fluid (CSF) in rats. (R) SCH-23390 produced up to a 50% decrease in net CSF production, compared to saline. This compound is a partial agonist at 5-HT1c serotonin receptors, and an antagonist at D1 dopamine receptors. The (S) enantiomer of SCH-23390 (SCH-23388) was ineffective. Drugs interacting with receptors for neurotransmitters in the choroid plexus may hold promise for the treatment of patients with increased intracranial pressure, including those with mass lesions, head trauma, acute or chronic hydrocephalus, or pseudotumor cerebri.

Abnormalities of the electron transport chain in idiopathic Parkinson's disease.

Idiopathic Parkinson's disease may have a low-level familial association but does not follow mendelian patterns of inheritance. Since inheritance of some components of the electron transport chain is nonmendelian and since inhibition of the electron transport chain with the toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine models Parkinson's disease in humans and animals, we evaluated catalytic activities of the electron transport chain in platelet mitochondria purified from patients with idiopathic Parkinson's disease. All 10 patients studied had significant reductions of complex I (NADH:ubiquinone oxidoreductase) activity. Succinate:cytochrome c oxidoreductase activity was less strikingly reduced. We hypothesize that the complex I abnormality may have an etiological role in the pathogenesis of Parkinson's disease and that this defect may be derived via the mitochondrial genome.

Quantitative autoradiographic localization of the D1 and D2 subtypes of dopamine receptors in rat brain.

The distribution of D1 and D2 receptors was studied in coronal sections of rat brain, using quantitative autoradiography. D1 receptors were labeled with 1.8 nM 3H-SKF-83566 (a brominated analog of 3H-SCH-23390), while D2 receptors were labeled with 1.0 nM 3H-spiroperidol (3H-SPD). The binding of both ligands to sections from brain and from a homogenate of caudate putamen (CPu mash) reached equilibrium within 80 min at 37 degrees C. CPu mash provided a virtually unlimited number of homogeneous sections that contained a high density of both D1 and D2 receptors. Sections of CPu mash were used in competition studies that confirmed that the specific binding of 3H-SKF-83566 was selective for D1 receptors, and that the binding of 3H-SPD was selective for D2 receptors. Scatchard analysis of equilibrium binding of the 2 ligands in the CPu in horizontal sections of rat brain revealed Kd values of 1.1 +/- 0.07 nM for 3H-SKF-83566 and 0.7 +/- 0.09 nM for 3H-SPD. Studies of the distribution of D1 and D2 receptors were carried out in coronal sections of brains from 5 rats. D1 receptors were found throughout the forebrain and were present in greater density than were D2 receptors in all regions examined except the olfactory nerve layer. In the CPu, nucleus accumbens, and olfactory tubercle, the densities of D1 and D2 receptors were, respectively, approximately 2,500 and 600-800 fmol/mg protein. In the substantia nigra, the density of D1 receptors was approximately 2,500 fmol/mg protein in both the compacta and the reticulata, but the density of D2 receptors was 230 fmol/mg protein in the compacta and 70 fmol/mg protein in the reticulata. The ventral tegmental area contained only 90 fmol/mg protein of D1 receptors, and D2 receptors were undetectable. The entopeduncular nucleus, zona incerta, and region of the ventral internal capsule had densities of D1 receptors of 550-950 fmol/mg protein and D2 receptor densities of less than 100 fmol/mg protein. Densities of D1 and D2 receptors were, respectively, 2,700 and 900 fmol/mg protein in the choroid plexus. Knowledge of the differences in the relative distributions of D1 and D2 receptors in various brain regions may increase our understanding of the functions of brain dopaminergic systems and may aid in the development of new therapeutic approaches for neuropsychiatric disorders.

Effects of chronic administration of neuroleptic and anticholinergic agents on densities of D2 dopamine and muscarinic cholinergic receptors in rat striatum.

It has been suggested that the development of tardive dyskinesia (TD), a serious and sometimes permanent movement disorder that may follow the use of neuroleptic drugs, is due to an increase in the density of or to a functional supersensitivity of D2 dopamine receptors in the striatum. The atypical neuroleptic clozapine (CLZ) is thought not to cause either acute extrapyramidal syndromes or TD because of its intrinsic anticholinergic activity. This hypothesis was examined using an increase in the density of striatal D2 dopamine receptors after chronic neuroleptic treatment in rats as a model of the changes underlying TD. Rats were treated for 14 days with saline; the neuroleptics CLZ, thioridazine or fluphenazine decanoate (FD); the anticholinergic drugs atropine or trihexyphenidyl or with FD together with atropine or trihexyphenidyl. Specific binding of [3H]spiroperidol to striatal D2 receptors was increased by 26 to 31% (P less than .05) in the groups treated with FD alone or in conjunction with any of the anticholinergic agents. There was no significant increase in the density of D2 receptors after administration of CLZ or thioridazine. The results are consistent with the hypothesis that an increase in the density of D2 receptors is associated with the development of TD. Because coadministration of anticholinergic drugs with FD does not attenuate the effects of the latter drug on striatal D2 receptors, it is likely that other properties of CLZ are responsible for its reduced propensity to produce alterations in D2 receptors and/or TD.

Effects of chronic treatment with selective and nonselective antagonists on the subtypes of dopamine receptors.

The effects of chronic blockade of D-1, D-2, or both subtypes of dopamine receptors on the densities and properties of the D-1 and D-2 subtypes of dopamine receptors were measured in rat brain. Animals were treated with 14 daily injections (i.p.) of the D-1-selective antagonist SCH-23390, the D-2-selective antagonist sulpiride, the nonselective antagonist fluphenazine, or vehicle. Serial 32-microns horizontal sections that included the caudate putamen were cut and alternately assigned to assays for D-1 or D-2 receptors. D-1 receptors were labeled with 3H-SKF-83566 or 3H-SCH-23390, and D-2 receptors were labeled with 3H-spiroperidol. Scatchard analysis was performed on the saturation data measured in the head of the caudate putamen to obtain estimates of receptor density. As expected, administration of the D-1-selective ligand SCH-23390 resulted in an increase in the density of D-1 receptors by approximately 47% and had no significant effect on the density of D-2 receptors. Similarly, administration of the D-2-selective ligand sulpiride resulted in an increase in the density of D-2 receptors by 25% and had no significant effect on the density of D-1 receptors. Thus the subtypes of dopamine receptors appear to be independently regulated after selective blockade. In contrast to the effects observed with selective antagonists, the results obtained with fluphenazine were more complex. Administration of the relatively nonselective antagonist fluphenazine resulted in an increase in the density of D-2 receptors by 51% but had no significant effect on the density of D-1 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet mitochondrial respiratory chain function in Parkinson's disease.

Reports on mitochondrial respiratory chain (MRC) complex I (CI) dysfunction in the substantia nigra in Parkinson's disease (PD) support the oxidative stress hypothesis in the neuropathogenesis of PD. Studies in peripheral tissue have found variable decreased CI and occasionally other complex activity suggestive of systemic impairment of MRC function in PD; however, MRC activity may be influenced by numerous variables. We conducted spectrophotometric measurements of MRC function in platelet mitochondrial preparations in 13 individuals with PD and 9 age-matched controls (CON) and have identified additional variables that may affect MRC activity. Mean CI, CIII, CIV, and citrate synthase (CS) activities were similar between PD and CON. CIII and CIV, specific and CS-corrected, activities were significantly positively correlated with CI in combined and individual group data, with the exception of CIII CS-corrected and CIV specific activities in CON and PD, respectively. CIII and CS specific activities were negatively correlated with age in CON, but varied randomly in PD. In PD, CIII specific activity was 1.4-fold higher in those with a history of environmental risk factors for PD and CIV specific activity was lower in those with a positive family history of PD [8.34 +/- 0.74 (n = 4) vs. 12.4 +/- 1.1 (SEM) min-1 mg-1; p = 0.046]. Group heterogeneity, variables affecting enzyme activity, and intrinsic properties of cells may thus contribute to conflicting data in studies of MRC function in platelets and other tissues.

Chronic treatment with levodopa and/or selegiline does not affect behavioral recovery induced by fetal ventral mesencephalic grafts in unilaterally 6-hydroxydopamine-lesioned rats.

It has been suggested that levodopa (L-dopa), a dopamine precursor used to treat Parkinson's disease, may be toxic to grafted fetal neuroblasts; if so, the use of the monoamine oxidase B inhibitor selegiline might prevent such toxicity. We randomly assigned 30 unilaterally 6-hydroxydopamine-lesioned male Sprague-Dawley rats, whose lesions were verified with low-dose apomorphine-induced rotations, to one of five treatment groups: (i) L-dopa methyl ester (125 mg/kg/day) with benserazide (a peripheral decarboxylase inhibitor; 25 mg/kg/day), (ii) L-dopa methyl ester with benserazide and selegiline (L-deprenyl; 0.5 mg/kg/day), (iii) selegiline only, (iv) and (v) vehicle (ascorbate in normal saline) only. After 2 weeks of twice-daily ip injections, the rats received fetal ventral mesencephalic grafts into the lesioned striatum; one vehicle group received sham grafts. Drug therapy was continued for 2 1/2 months post grafting. At 1 month after grafting, and every 2 weeks thereafter, the rats were tested using low-dose apomorphine-induced rotation. A 70% decrease in rotations among all grafted groups, relative to the shams, was found. No statistical differences among groups receiving various drug therapies were seen in behavior or in counts or dimensions of tyrosine hydroxylase-positive cells. We therefore conclude that, in the unilaterally lesioned rat model of Parkinson's disease, there is no adverse effect of L-dopa nor any significant effect of selegiline, either alone or coadministered with L-dopa, on behavioral recovery induced by fetal ventral mesencephalic grafts.

Sensitization to cocaine in the nigrostriatal dopamine system.

Behavioral sensitization involving the nigrostriatal dopaminergic tract is manifested after treatment with only a single dose of cocaine and is augmented following repeated treatment. One neurochemical change observed that is consistent with behavioral sensitization is the increase in amphetamine-induced 3H-DA release from striatal slices seen after one injection of cocaine. One day after repeated administration of cocaine, however, the increase is no longer evident. It is possible that transient compensatory changes, such as increased D-2 autoreceptor inhibition, may obscure this effect when it is measured at relatively short times after the repeated administration has been terminated. One day after cessation of repeated cocaine administration, D-2 autoreceptors in both striatum and substantia nigra compacta were upregulated consistent with a compensatory mechanism and the development of behavioral tolerance rather than sensitization. In contrast, DA content, neuronal DA uptake, and postsynaptic D-2 DA receptors in striatum were not regulated by this treatment. Likewise, D-1 DA receptors in striatum and substantia nigra were unaffected. In the mesolimbic system, both the pre- and postsynaptic receptor changes are consistent with sensitization. Amphetamine-stimulated release from nucleus accumbens has not yet been measured in cocaine-sensitized animals. It is possible that changes similar to those seen in striatum may occur in this area. It is interesting that, in general, presynaptic parameters associated with the DA neuron, with the notable exception of the uptake pump, appear to be more sensitive to regulation by cocaine administration than do postsynaptic parameters. The long-lasting effects of a single moderate dose of cocaine are also surprising. It will be important to determine the molecular mechanisms underlying this regulation and whether or not similar changes are induced in mesolimbic dopaminergic systems by single and repeated administration of cocaine.

Persistence of neurochemical changes in dopamine systems after repeated cocaine administration.

The purpose of this study was to test whether persistent changes consistent with behavioral sensitization occur in dopamine (DA) uptake, release or receptors following repeated cocaine administration. Our neurochemical experiments focused primarily on the striatum; however, quantitative autoradiography was used to measure D-1 and D-2 DA receptors in both cell body and terminal regions of the nigrostriatal and mesolimbic dopaminergic pathways. After receiving eight once-daily injections of cocaine (10 mg/kg, i.p.), rats remained behaviorally sensitized for 1 week. This repeated treatment with cocaine induced two changes consistent with increased dopaminergic transmission. Postsynaptic D-2 DA receptors were selectively increased in nucleus accumbens one day after termination of the repeated cocaine administration; however, these receptors returned to control levels one week after cocaine administration had been terminated. In contrast, amphetamine-stimulated [3H] DA release from striatal slices was increased in rats receiving repeated cocaine injections, but this increase was not apparent until 1 week after the drug administration had been terminated. While neither of these two changes is sufficient to explain cocaine-induced behavioral sensitization, both are consistent with increased dopaminergic responsiveness and may contribute to sensitization.