The central neurotropic activity of an aqueous-alcoholic extract from Rhaponticum carthamoides (Wilid.) (Leucea carthamoides D.C.) cultivated in Bulgaria was studied in experiments on albino mice, rats and cats. In doses up to 40 g/kg the extract was non-toxic. Administered in definite doses in mice and rats, it exerted a moderate central stimulating action: increased ambulation and rearing in rats ("open field" test); increased central nervous system excitability ("jumping" test); had a slight antinarcotic effect; improved learning and memory in rats trained in a maze; and increased the physical strength of rats subjected to exhaustive swimming. Administered intraduodenally in cats the extract exerted a hypotensive effect.

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The effect of orotic acid and central stimulants on retention of shuttle-box avoidance was investigated in rats. Orotic acid (100 mg/kg) was injected 30 min before training; caffeine (20mg/kg), strychnine (1 mg/kg), or methylphenidate (10 mg/kg) were injected immediately after training. When given alone, these drugs improved avoidance retention when tested 24 h after training. However, improvement of retention was much more evident when orotic acid was given in combination with a stimulant. The data are discussed in relation to the role of macromolecule synthesis and arousal in memory formation.

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