Abstract

Histamine neurons, motility and feeding behaviour

Phase shift of circadian activity

Excitability of neurons, convulsive phenomena

Effects of histamine on the arousal system

References

Discussion
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The circadian rhythm of motility in rodents correlates with neuronal histamine release and depends on the integrity of the histaminergic tone. In the CSF of children the concentration of t-methylhistamine (MH), the main metabolite of histamine was highest during daytime suggesting that also in humans high histamine release is connected with periods of arousal. Histaminergic stimulation has anticonvulsant effects in rats and mice while a low level of histamine in the CSF seems to render children susceptible to febrile seizures. In rats, the brain histaminergic activity was increased by a portacaval shunt (PCA) which raises histamine and MH concentrations, or by H3 receptor antagonist thioperamide which induces histamine release. Frontal cortex EEG in freely behaving rats showed that PCA-rats spent significantly more time in aroused state (desynchronized EEG), whereas the opposite was true with the signs of drowsiness (delta waves and spindles). Thioperamide reduced the incidence of thalamus-regulated EEG spindles and the spectral power of the low-frequency (1.5-5 Hz) EEG. MH levels correlated well with the degree of thioperamide- induced reduction of slow-wave EEG activity. All these results link histaminergic activity to the neocortical synchronization associated with the control of arousal.

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Presentation Number SAtuomisto0834
Keywords: histamine, EEG, circadian rhythm, portacaval shunt, seizure