Use of neurotoxins to study Ca2+ channel functions

The article contains a brief review on the properties and classification of voltage-dependent Ca2+ channels and on the organic blockers of the different channel types. The effects of peptide toxins from the venoms of Conus sp and of the spider Agelenopsis aperta on high voltage-activated Ca2+ channels are discussed. In addition, we present preliminary data on a novel peptide toxin purified from the venom of the spider Phoneutria nigriventer, which is a powerful blocker of L-and N-type Ca2+ channels.

Remarkable similarities between the temporal organization of neocortical electrographic sleep patterns of rats and humans

Electrocorticographic activity was automatically recorded in albino rats for 72 consecutive h and analyzed by procedures suitable to detect 24-h rhythms. Beta (alert wakefulness), theta (somnolence), delta (slow wave sleep) and sigma 1 (superficial synchronized sleep) activities showed a robust circadian rhythmic distribution. The acrophases (maxima of the adjusted cosine curve) occurred at 23:39, 07:59, 08:37 and 13:25 h, respectively. EMG atonia and extreme hypotonia (less than 10% of mean EMG level) episodes showed a 24-h rhythm peaking at 14:18 h. The temporal sequence within the circadian rest period, i.e., somnolence, slow, wave sleep, superficial synchronized sleep and paradoxical sleep, is very similar to that known to occur during the nocturnal sleep of humans

Lack of similarity between the effect of lesions of the suprachcasmatic nucleus and subparaventricular hypothalamic zone on behavioral circadian rhythms

Rats were submitted to eletrolytic lesion of either the suprachiasmatic nucleus (SCN) or the subparaventricular hypothalamic zone (SPVH) and the effects on circadian behavioral rhythms were compared. While the SCN lesion abolished the circadian rythmicity of all behavioral patterns, the SPVH lesion only abolished that of the eating and drinking behavior and reduced the amplitude of a behavioral item usually associated with REM sleep