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Cerebral monoaminergic neurotransmitters and their metabolites show various concentration changes in gerbils following bilateral carotid ligation. The present study evaluated the effect of chronic administrations of lisuride hydrogen maleate (lisuride) on these changes. Lisuride (0.01 mg/kg or 0.05 mg/kg) or vehicle was intraperitoneally administered to gerbils for 14 consecutive days before the induction of a 30 min ischemia by bilateral carotid ligation. Animals were sacrified immediately and the levels of dopamine, DOPAC, homovanillic acid, noradrenaline, serotonin and 5-hydroxyindoleacetic acid determined by HPLC in the striatum, cortex, hippocampus and diencephalon/midbrain. Lisuride itself had no effect on any compound determined in any region. In the carotid-ligated gerbil brain, however, lisuride corrected the reduction of dopamine in the striatum, normalized or reduced increases in the (DOPAC+homovanillic acid)/dopamine ratio in the striatum, hippocampus and diencephalon/midbrain, and increased the levels of serotonin in all four regions. The present study, together with previous reports, indicate that lisuride may interfere with ischemia-induced cerebrovascular disturbances and, in such a way, improve some pathological sequelae of cerebrovascular disease.

Bifemelane hydrochloride (bifemelane), idebenone and indeloxazine hydrochloride (indeloxazine) are used clinically to reduce apathy and other emotional disturbances in patients with cerebrovascular disease. In gerbil brains, ischemia affects many monoaminergic neurotransmitters and their metabolites. In the present study, the effects of treatment with bifemelane, idebenone and indeloxazine on ischemia-induced changes in monoamines and their metabolites were studied in ischemic gerbil brains. Although these drugs had no effect on the monoaminergic neurotransmitters or their metabolites in sham-operated animals, in the ischemic brains both dopamine and serotonin turnovers were abnormal after idebenone or indeloxazine treatment. Bifemelane, in contrast, tended to correct the ischemia-induced changes in the dopaminergic and serotonergic systems in the cerebral cortex, hippocampus and thalamus + midbrain. From the present results and those in previous reports, we conclude that bifemelane is more appropriate than idebenone or indeloxazine as a treatment for the ischemia-induced changes in monoaminergic neurotransmitter systems.

The effects of bifemelane hydrochloride on changes of N-methyl-D-aspartate receptors and muscarinic cholinergic receptors were examined in the gerbil hippocampus after transient ischemia with radioactive-specific ligands. There were marked reductions in both these receptors in the gerbil hippocampus 14 days after transient ischemia, without changes in the respective affinities. Post-ischemia bifemelane treatment almost completely prevented the ischemia-induced decreases in the numbers of these receptors, and had no effect in sham-operated controls. The results of the present study suggest that this drug prevents postsynaptic dysfunction induced by transient ischemia, and may be useful in the therapy of both the chronic and the acute stage of cerebrovascular disease.

To clarify the interactions between dopamine receptors and muscarinic cholinergic receptors by which neurotransmitters may affect genetic responses, we studied the effects of the muscarinic cholinergic agonist, carbachol, and the muscarinic cholinergic antagonist, trihexyphenidyl, on levodopa-induced c-fos messenger RNA (mRNA) expression in rat striatum. Animals were administered levodopa (levodopa with one-tenth dosage of carbidopa), carbachol or thrihexyphenidyl alone or administered in combination as levodopa (100 mg/kg) + carbachol, or levodopa+trihexyphenidyl given as a single bolus. Levodopa given alone increase the expression of c-fos mRNA. Although carbachol or trihexyphenidyl alone was ineffective in inducing c-fos mRNA, the combination of levodopa and carbachol (> or = to 0.1 mg/kg) significantly suppressed the induction of c-fos mRNA as compared with levodopa given alone. The combined administration of levodopa and trihexyphenidyl showed a trend toward an additive effect on the induction of c-fos mRNA vs levodopa alone. These findings suggest that the muscarinic cholinergic system may modulate the levodopa-induced c-fos mRNA expression which then regulates the expression of other mRNAs.

We studied the distribution of the rat brain beta-2 adrenergic receptor (AR) mRNA, and the effects of monoamine depletions by chronic reserpine treatment using in situ hybridization histochemistry. In the control group, high level signals of beta-2 AR mRNA were observed in the parietal, frontal and piriform cortices, the medial septal nuclei, the olfactory tubercle, and the midbrain. Moderate signals were found in the striatum, the retrosplenial cortex, the hippocampus, and the thalamic nuclei. After chronic reserpine treatment, beta-2 AR mRNA levels were increased in many brain regions. The large increases were seen in the hippocampus, all thalamic nuclei, the amygdaloid nuclei, and the midbrain, followed by the striatum and the occipital cortex. The receptor up-regulation resulting from chronic monoamine depletion may be due to these increases in beta-2 AR mRNA, indicating that this up-regulation may be caused by increased receptor production rather than decreased receptor degradation.

The calcium (Ca) antagonist flunarizine hydrochloride (FNZ) has been reported to induce parkinsonism, especially in the elderly. The effects of FNZ on dopamine receptors in rat striatal membranes, especially in aged rats, were studied using radiolabeled receptor assay. Similar displacing potencies in [(3)H]spiperone bindings were exhibited for FNZ and the Ca antagonists verapamil and nicardipine. FNZ was found to directly and competitively effect D2 receptors (D2-Rs) as an antagonist, without effecting D1 receptors. Furthermore, the washing of preoccupied membranes revealed that FNZ has a long-acting potent effect on D2-Rs. The comparative study of FNZ and sulpiride in young-adult and aged rats showed that the effect of FNZ on D2-Rs was more marked in aged rats. These results might be related to FNZ-induced parkinsonism and its high incidence in the elderly.

To gain further insight into the central nervous system (CNS)-action of beta-adrenergic blocking agents (beta-blockers), we examined the effects of various kinds of beta-blockers on opioid receptors (Op-Rs) using radiolabeled receptor assay (RRA). We demonstrated that beta-blockers are competitively bound to Op-Rs in the CNS. Sodium index of beta-blockers in [3H]naloxone binding study indicated that beta-blockers had the mixed agonist-antagonist activity of opiates. The relative potency of beta-blockers in opioid RRA was negatively correlated with their membrane stabilizing activity. Neither beta-blocking activity nor intrinsic sympathomimetic activity was correlated with IC50 values of beta-blockers in opioid RRA. While it is widely accepted that beta-blockers have a tranquilizing activity, a part of the tranquilizing action of beta-blockers may be mediated through Op-Rs in the CNS. Although beta-blockers may have effects on their own receptors (beta-receptors) in the CNS, the more precise mechanisms of central action of these drugs must be further investigated.

The dopamine system in weaver mutant mice, a model of cerebellar atrophy, was studied. Dopamine levels of 6-week-old weaver mice were 37%, 44%, 34%, and 41% of levels in age-matched controls in the cerebral cortex, hippocampus, septal region and striatum, respectively. Noradrenaline levels did not differ from controls. This study shows that weaver mice have specific deficiencies in the dopamine system.

In a model of dyskinesia induced by the administration of iminodipropionitrile (IDPN) in the rat, we evaluated the effects of ceruletide, an analogue of cholecystokinin, on behavioral abnormalities and monoaminergic neuronal function. Vertical head twitching in the IDPN-treated animals was inhibited for over 5 h following a single subcutaneous dose of 160 micrograms/kg ceruletide. In animals dosed daily for 2 or 3 days, the number of head twitches at 24 h after the last dose was about one-third of the number before treatment. After repeated daily doses of ceruletide for 6 days, the number of head twitches was reduced to low levels and remained significantly below pretreatment levels until the 4th posttreatment day. These results indicate that the inhibition of dyskinesia by ceruletide was long-lasting. Assays of monoaminergic neurotransmitters and their metabolites in various brain regions indicate that an imbalance between dopaminergic and serotonergic neuronal systems plays a major role in the pathogenesis of the IDPN-induced dyskinesia, i.e. the ratio of (DOPAC+HVA)/5-HIAA was significantly greater in the striatum but significantly smaller in the hippocampus of the IDPN-treated vs normal animals. This initially abnormal ratio of (DOPAC+HVA)/5-HIAA in the striatum and hippocampus of IDPN-treated animals returned to normal following treatment with ceruletide, corresponding with the reduction of the head twitching. The alterations in monoaminergic neuronal function induced by repeated administration of ceruletide persisted for at least 3 days, even though its plasma half-life is several minutes. Ceruletide also exerted a marked effect on monoaminergic neuronal function in the IDPN-treated rats, in contrast to only a slight effect in normal animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the regional density of muscarinic-1 (M1) receptors and the effect of lisuride hydrogen maleate on these changes were studied in senescent rat brain by in vitro autoradiography. In young adult controls, M1 receptor binding was most dense in the striatum and hippocampus, followed by the cerebral cortex and amygdala. Binding to M1 receptors was markedly lower in these areas of the senescent brain compared with the young adult brain. These decreases were reversed by intraperitoneal administration of 50 micrograms/kg.day lisuride for 14 days. The present results indicate that the therapeutic efficacy of lisuride depends on normalization of not only monoamine systems but also acetylcholine systems.

Although neuronal death following brain ischemia was originally considered to be due to an energy deficiency resulting from an impaired respiratory chain, the observation of "delayed neuronal death" indicated some other factor. It is believed that delayed neuronal death after transient forebrain ischemia appears as a result of release of glutamate, an excitatory amino acid. In the present study, transient ischemia for 20 minutes in a rat four-vessel occlusion model was induced, and serial changes in histology and N-methyl-D-aspartate receptor (NMDA-R) binding were evaluated up to the chronic stage. Destruction of pyramidal cells and extensive astrocytic proliferation in the CA1 area of the hippocampus was completed by 10 days after cerebral ischemia followed by cerebral blood recirculation. However, the glutamate receptor subtype, NMDA-R, showed no change in all brain regions until after 10 days, but decreased in the hippocampus to 50% after 21 days despite no evidence of histological progression of neuronal death. The results show that the time course for appearance of light microscopic damage in the hippocampal region does not parallel that for depletion of NMDA-R binding sites.

Changes in the distribution and densities of somatostatin receptors (SS-R) in young adult and aged rat brain and the effects of chronic administration of bifemelane hydrochloride (bifemelane) on these changes were studied by in vitro quantitative autoradiography of iodinated [Tyr11] SS-14. SS-R was highest in density in the amygdala, followed by the cingulate cortex, temporal cortex, frontal cortex, hippocampus and septal nucleus in the young adult rats. In contrast, SS-R binding was markedly reduced in the frontal cortex, temporal cortex, cingulate cortex, hippocampus, amygdala and septal nucleus of aged rats compared to young adult rats. However chronic administration of bifemelane significantly increased SS-R binding in the frontal cortex, temporal cortex, cingulate cortex, hippocampus and septal nucleus of aged rats without effects on young adult rats. This bifemelane-induced increase in SS-R is considered to have important implications in the mechanism of the therapeutic efficacy of bifemelane.

In senescent rats, the binding ability of muscarinic cholinergic receptors (MCR) was markedly decreased in the cerebral cortex, hippocampus, thalamus, and the striatum compared with young adult rats. This decrease was markedly improved by chronic administration of bifemelane hydrochloride (bifemelane). In view of the findings that bifemelane markedly inhibits the decrease in acetylcholine (ACh) associated with cerebral ischemia, and that it improves amnesia induced by scopalamine, it may be inferred that bifemelane acts on the pre- and post-synaptic ACh neuronal systems. It may improve memory disturbance due to aging or cerebral ischemia, decreased conscious level, and decreased motor function.

Regional responses of rat brain opioid receptors (Op-Rs) upon castration and testosterone replacement were studied using [3H]naloxone (NAL) binding for u-type and [3H]D-Ala2-methionine-enkephalin (ENK) binding for delta-type Op-R. Castration itself produced an increase in specific NAL and ENK binding in the olfactory bulb and thalamus + midbrain. In the hypothalamus, specific ENK binding was increased without any change in NAL binding. After the testosterone replacement in castrated rats, specific NAL binding was decreased and returned to the control level in the thalamus + midbrain, but remained high in the olfactory bulb. Specific ENK binding was decreased and returned to the control level in the olfactory bulb, hypothalamus and thalamus + midbrain. These results indicated that there are regional differences between u- and delta-type Op-R responses to castration and testosterone replacement. Op-R subtypes were regulated differentially by endogenous hormonal changes, such as testosterone.

We examined the changes in the concentrations of neuropeptides in various regions of the mouse brain 1, 2 or 6 weeks after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment (30 mg/kg i.p. twice/day for 5 days) and further examined the effects of levodopa injections (200 mg/kg i.p.) for 14 days starting 4 weeks after MPTP treatment on regional somatostatin (SRIF) concentrations. Substance P, cholecystokinin-octapeptide and thyrotropin-releasing hormone did not show any significant changes up to 6 weeks after MPTP treatment, whereas the SRIF concentration increased 1 week after MPTP treatment but decreased thereafter, showing a marked decrease in the striatum and hippocampus after 6 weeks. In the striatum, the decreased concentration of SRIF recovered to the normal level with levodopa injections. This SRIF depletion could be a change secondary to dopamine depletion. On the other hand, in the cerebral cortex, while showing no change in the SRIF concentration after MPTP treatment, the concentration decreased significantly with levodopa injections. In the hippocampus, the decreased SRIF levels were still low after levodopa treatment. Since it has been reported that SRIF concentrations are significantly reduced in the frontal cortex and hippocampus of demented parkinsonians and patients with senile dementia of the Alzheimer type and that levodopa treatment induced various psychiatric side effects, the results of the present study suggest some relationship among levodopa treatment, SRIF depletion and the demented state.

In situ hybridization histochemistry, using the alpha-tubulin oligonucleotide probe, was performed employing two tissue freezing methods, the preperfuse-freezing method and the freshly frozen method, to evaluate methodological differences in the messenger RNA (mRNA) levels of the brain. The mRNA levels in the sections from the freshly frozen groups were lower than those in the preperfused group, particularly in the cerebral cortex, the striatum, the hippocampal Ca1 and CA4 fields, and the habenular nuclei. Therefore, employing the freshly frozen method, there is a possibility that the mRNA levels in these regions may be underestimated. The hybridization signals of groups placed on an ice-bed for 5 min and 15 min were lower than those of the immediately frozen group in the cingulate, the temporal, and the retrosplenial cortex, the CA1 field, and even in the medial and the lateral thalamic nuclei where no significant difference was seen between the perfused group and the immediately frozen group of tissues. When employing the freshly frozen method, the removed brain should be frozen as fast as possible and the period from decapitation to freezing should be kept strictly constant.

Changes in various neurotransmitter systems of the gerbil brain during ischemia and the effects of administration of mergocryptine, a new ergot derivative, were studied. Gerbils intraperitoneally administered 0.5 mg/kg of mergocryptine or the vehicle once a day for 14 days were used. The administration of mergocryptine to control animals had no effect on the contents of neurotransmitters or their metabolites in various regions of the brain, but it corrected abnormalities in the neurotransmitter systems caused by ischemia. These results suggest the usefulness of mergocryptine against the deleterious effects of brain ischemia.

Flunarizine hydrochloride (FZ) is used to improve cerebral circulation and possesses Ca antagonistic effects. In recent years, this drug has been reported to induce parkinsonism and depressive symptoms as side effects, particularly in the elderly. Effects of FZ on dopamine receptors of the rat striatum were studied by radiolabeled receptor assay to clarify the mechanism of onset of parkinsonism in response to FZ. FZ was found to directly and competitively affect D-2 receptors without affecting D-1 receptors. Furthermore, the effect of FZ on D-2 receptors was found to be antagonistic based on the finding that the displacement curve for FZ in the binding of [3H]spiperone to D-2 receptors remained unchanged even after the addition of GppNHp. The effect of FZ on the D-2 receptors in aged rats was more marked than that in young-adult rats. In addition, the tertiary structures of FZ and the anti-schizophrenic agents, pimozide and haloperidol, were examined using computer graphics. FZ was found to have a tertiary structure highly analogous to pimozide and haloperidol, and FZ also had an alkyl structure linking a fluorophenyl group and a nitrogen atom, believed to be particularly necessary for the binding of anti-schizophrenic agents to D-2 receptors. These results may contribute to clarifying the mechanism of onset of parkinsonism in response to FZ, especially in the elderly.