Brain transaminases in a chemically induced behavioral abnormality

Neuropeptide levels in discrete brain regions in the iminodipropionitrile-induced persistent dyskinesia rat model

To clarify the role of neuropeptides in dyskinesia induced by iminodipropionitrile (IDPN), the levels of five representative neuropeptides were examined in discrete regions of the rat brain 4 weeks after intraperitoneal injection of IDPN. The five neuropeptides examined were methionine-enkephalin (Met-Enk), substance P (SP) and somatostatin, which are closely related to extrapyramidal function, and thyrotropin-releasing hormone (TRH) and cholecystokinin octapeptide (CCK-8), which are closely related to the neural mechanism of the dopamine system. IDPN pretreatment significantly increased Met-Enk in the basal ganglia but not SP or somatostatin; however, all three neuropeptide levels were increased in the hindbrain. In IDPN-treated rats, TRH and CCK-8 levels were increased in the nucleus accumbens, and the frontal cortical CCK-8 level was extremely increased. These findings, together with previous reports, suggest that neuropeptides in the basal ganglia, hindbrain and cerebral cortex play important roles in the manifestation of dyskinetic symptoms.

Long-lasting effect of ceruletide on dyskinesia and monoaminergic neuronal pathways in rats treated with iminodipropionitrile

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)

Behavioural effects of beta,beta'-iminodipropionitrile (IDPN) in the domestic fowl (Gallus domesticus)

The behavioural effects of beta,beta'-iminodipropionitrile (IDPN) were studied in chicks and adult fowls. Repeated administration of IDPN (75 mg/kg) for 5 days induced behavioural changes in chicks and adult fowls characterized by excitation, choreiform head and neck movements and circling (ECC-syndrome). Both acute and chronic administration of IDPN induced EEG desynchronization, EMG activation and enhancement of photic-evoked response (PER) in the hyperstriatum and pontine reticular formation while a decrease in PER was observed in the optic tectum. d-Amphetamine (2.5-5 mg/kg), apomorphine (0.1-0.25 mg/kg), piribedil (2.5-5 mg/kg), atropine (2.5-5 mg/kg), hyoscine (2.5-5 mg/kg) and cyproheptadine (0.5 mg/kg) potentiated the circling and choreiform head and neck movements. These activities were antagonized by pimozide (1 mg/kg), physostigmine (0.5 mg/kg) and quipazine (2.5-5 mg/kg). The results suggest that dopaminergic, serotoninergic and cholinergic mechanisms may be involved in IDPN-induced behavioural effects in chicks.

Quipazine exacerbation of a hyperkinetic syndrome: involvement of brain dopamine and serotonin

Quipazine (5-25 mg.kg-1, s.c.) was given to rats in which a hyperkinetic syndrome had been previously induced by administration of beta,beta'-iminodipropionitrile (IDPN). Quipazine produced a significant increase in the circling behavior and choreiform head and neck movements, characteristic of the syndrome. This response could be blocked by pretreatment with the serotonin antagonists, SQ10, 631 (25 mg.kg-1, i.p.) and methysergide (5.0 mg.kg-1, i.p.), as well as the dopamine receptor antagonist, haloperidol (0.5 mg.kg-1, i.p.). These observations are discussed with respect to the nature of the involvement of brain serotonergic and dopaminergic systems in quipazine action on these hyperkinetic disturbances.

Regional neurochemical studies on the effect of beta, beta'-iminodipropionitrile (IDPN) in the rat

A permanent hyperkinetic syndrome, characterized by excitation, choreiform head and neck movements and circling, which has led to it being called collectively the "ECC-syndrome," is induced in rats by the daily IP administration of beta, beta'-iminodipropionitrile (IDPN), 300 mg/kg, for 7 days. The levels of the biogenic amines, norepinephrine (NE), dopamine (DA), serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), were measured in the striatum, midbrain, medulla, cortex, and cerebellum on the day the syndrome appeared (day 7) and one week later (day 14). The biogenic amine most affected by IDPN administration was 5-HT. On day 7, striatal 5-HT levels increased and 5-HIAA levels decreased while in the medulla and midbrain, 5-HIAA levels increased. On day 14, significant reductions in both 5-HT, in the midbrain, striatum, and cortex, and 5-HIAA, in all regions except the cortex, were observed. NE was markedly increased in the medulla, midbrain, and striatum on day 7, whereas on day 14 it was found to be within the normal range in these same regions. With the exception of a slight, but significant, increase in the cortex on day 7, DA levels in all regions were found to be relatively unaffected by IDPN administration on both day 7 and day 14. In an attempt to detect degenerative changes which might be taking place in the brain and which might provide an explanation for the permanency of the behavioral disturbances, the uptake of [3H]-labeled NE, DA, and 5-HT into synaptosomal-rich preparations of striatum and the uptake of NE and 5-HT into the midbrain area were compared between normal and syndromized rats on both day 7 and day 14. Small changes were observed but they were not statistically significant. The alterations of 5-HT and 5-HIAA levels in several regions of the brain under the conditions examined may indicate that IDPN's neurotoxicity primarily affects 5-HT-containing neurones. The active membrane transporting system of the nerve endings studied, however, remained relatively intact. This latter finding eliminates the possibility that neuronal degeneration in these areas is responsible for the decreased 5-HT and 5-HIAA levels or is the pathology underlying the permanency of the syndrome. These results are evaluated in terms of a possible model for hyperkinetic disorders.