The effect of vincamine, hydergine and piracetam on the firing rate of locus coeruleus neurons

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Abstract
Vincamine, hydergine and piracetam are used for the treatment of memory disturbances as well as for the treatment of various other brain dysfunctions seen in the elderly patient. The action of these three psychogeriatric compounds on the activity of noradrenergic neurons in the rat locus coeruleus was investigated. All three compounds, when administered intraperitoneally, increased the firing rate of noradrenergic neurons in the chloral hydrate anaesthetized animals. Vincamine and hydergine had a similar potency producing a maximal mean increase of about 70% at a dose of 1mg/kg. Likewise, piracetam was significantly less potent eliciting a 30 to 40 % increase in firing at doses of 300 and 1000 mg/kg, respectively. A role for the locus coeruleus in processes related to attention, cortical and behavioral arousal, learning and memory has been proposed on the basis of behavioral and electrophysiological experiments. In the awake rat, the firing rate of noradrenergic neurons in this brain nucleus has previously been shown to relate directly to the level of vigilance. The activating action of vincamine, hydergine and piracetam on these neurons may be linked with some of the drugs' beneficial therapeutic effects.