Appearance of intoxication in rats by intraperitoneal administration of clioquinol

Pharmacokinetics and distribution of clioquinol in golden hamsters

Clioquinol (5-chloro-7-iodo-8-quinolinol) is a zinc and copper chelator that can dissolve amyloid deposits and may be beneficial in Alzheimer's disease. Prion diseases are also degenerative CNS disorders characterised by amyloid deposits. The pharmacokinetics and tissue distribution of drugs active against prions may clarify their targets of action. We describe the pharmacokinetics of clioquinol in hamster plasma, spleen and brain after single and repeated oral or intraperitoneal administration (50 mg kg(-1)), as well as after administration with the diet. A single intraperitoneal administration led to peak plasma clioquinol concentrations after 15 min (Tmax), followed by a decay with an apparent half-life of 2.20 +/- 1.1 h. After oral administration, Tmax was reached after 30 min and was followed by a similar process of decay; the AUC(0-last) was 16% that recorded after intraperitoneal administration. The Cmax and AUC values in spleen after a single administration were about 65% (i.p.) and 25% (p.o.) those observed in blood; those in liver were 35% (p.o.) those observed in blood and those in brain were 20% (i.p.) and 10% (p.o.) those observed in plasma. After repeated oral doses, the plasma, brain and spleen concentrations were similar to those observed at the same times after a single dose. One hour after intraperitoneal dosing, clioquinol was also found in the ventricular CSF. Clioquinol was also given with the diet; its morning and afternoon concentrations were similar, and matched those after oral administration. No toxicity was found after chronic administration. Our results indicate that clioquinol, after oral administration with the diet, reaches concentrations in brain and peripheral tissues (particularly spleen) that can be considered effective in preventing prion accumulation, but are at least ten times lower than those likely to cause toxicity.

Oral administration of metal chelator ameliorates motor dysfunction after a small hemorrhage near the internal capsule in rat

Cerebral hemorrhage leads to local production of free iron, radicals, cytokines, etc. To investigate whether a decrease of iron-mediated radical production influences functional recovery after intracerebral hemorrhage (ICH), a modified ICH rat model with a small hemorrhage near the internal capsule (IC) accompanied with relatively severe motor dysfunction was first developed. Then clioquinol (CQ), an iron chelator that reduces hydroxyl radical production, was orally administrated. Injection of different doses of Type IV collagenase (1.4 mul 1-200 U/ml) into the left striatum near the IC in Wistar rats showed that injection of 7.5 U/ml collagenase resulted in a small hemorrhoidal lesion near the IC with relatively severe motor dysfunction (IC model). Retrograde labeling of neurons in the sensory-motor cortex and axons in the corticospinal tract using Fluoro-gold (FG) injection into the spinal cord (C3-C4) showed that few labeled neurons in the sensory-motor cortex were detected in the IC model, FG-labeled axons disappeared, and FG-including ED-1-positive cells appeared within 24 hr in the IC. Assessments of behavior and histologic analysis after oral administration of CQ in the IC model indicated that oral administration of CQ prevented a decrease of FG-labeled neurons, and resulted in better motor-function recovery. CQ inhibited hydrogen peroxide-induced cell toxicity in oligodendrocytes in vitro, but not in neurons. Our data suggests that CQ ameliorated motor dysfunction after a small hemorrhage near the IC by a mechanism that is related to reduction of chain-reactive hydroxyl radical production in oligodendrocytes.

Auditory and colored visual P300 in patients with sequelae of subacute myelo-optico-neuropathy

To study the cognitive function in 13 patients with sequelae of subacute myelo-optico-neuropathy (SMON), event-related potentials (ERPs) were elicited with tones, clicks, and colored visual stimuli in different tasks. P300 latency was delayed, and P300 amplitude reduced or absent in 5 patients (38%), although neuropsychological assessment for dementia did not differ between patients and 21 age-matched normal controls. P300 and N200 latencies with the tone/tone auditory stimuli and N200 latency with the visual stimuli were significantly delayed, but the latencies of early components (N100 and P200) were not delayed. These findings suggest that SMON patients may have cognitive dysfunction to a slight degree.

Selective neurotoxicity of clioquinol on the function of the posterior column nuclei

In the gracile nucleus of clioquinol-treated rats, the presynaptic inhibition was remarkably diminished, and the excitatory synaptic transmission was less intensely inhibited by a conditioning sural nerve volley. These changes may be the pathophysiology responsible for paresthesia and/or dysesthesia in patients with subacute optico-myelo-neuropathy (SMON).