Neuronal damage in the albino rat: excitotoxin, microtubule inhibitor synergism

The microtubule interacting drug candidate NAP protects against kainic acid toxicity in a rat model of epilepsy

NAP (NAPVSIPQ, generic name, davunetide), a neuroprotective peptide in clinical development for neuroprotection against Alzheimer's disease and other neurodegenerative indications, has been recently shown to provide protection against kainic acid excitotoxicity in hippocampal neuronal cultures. In vivo, kainic acid toxicity models status epilepticus that is associated with hippocampal cell death. Kainic acid toxicity has been previously suggested to involve the microtubule cytoskeleton and NAP is a microtubule-interacting drug candidate. In the current study, kainic acid-treated rats showed epileptic seizures and neuronal death. Injection of NAP into the dentate gyrus partially protected against kainic acid-induced CA3 neuron death. Microarray analysis (composed of > 31 000 probe sets, analyzing over 30 000 transcripts and variants from over 25 000 well-substantiated rat genes) in the kainic acid-injured rat brain revealed multiple changes in gene expression, which were prevented, in part, by NAP treatment. Selected transcripts were further verified by reverse transcription coupled with quantitative real-time polymerase chain reaction. Importantly, among the transcripts regulated by NAP were key genes associated with proconvulsant properties and with long-lasting changes that underlie the epileptic state, including activin A receptor (associated with apoptosis), neurotensin (associated with proper neurotransmission) and the Wolfram syndrome 1 homolog (human, associated with neurodegeneration). These data suggest that NAP may provide neuroprotection in one of the most serious neurological conditions, epilepsy.

Microtubule disruption and cognitive defects: effect of colchicine on learning behavior in rats

Neuropathological findings in Alzheimer's disease (AD) suggest a possible involvement of microtubule dysfunction in neurodegenerative process pathogenesis. Because microtubules have a major role in neuronal plasticity, microtubule disruption could be also directly responsible for cognitive defects in AD. We report that in rats, continuous microtubule disruption induced by chronic colchicine administration results in a dose-dependent learning deficit. In addition, retention is also impaired. These cognitive defects are specific, as chronic colchicine induces no other behavioral toxicity within the study dose range. Colchicine-induced cognitive defects resemble those of AD, which are characterised by amnesia of recent learning and loss of formerly established memories. This new procedure of pharmacologically induced cognitive impairment may prove useful, both towards understanding AD pathogenesis and towards drug screening.

Astrocytes: a possible primary site for colchicine-mediated neurotoxicity in the rat striatum

Ultrastructural changes in rat astrocytes including endfoot swelling and rupture of plasma membranes were seen as early as 1 h after injection of 6.0 micrograms colchicine (CO) into the striatum. Significant change in neuronal morphology was not seen by 24 h. Astrocytes may therefore be primary targets for CO-mediated damage, which then may have secondary neurotoxic consequences.