Another important property of Bacopa, dependent on its effects on the central nervous system, is its anti-convulsive action.
One study evaluated the anti-convulsive effects of Bacopa monnieri in the prevention of epileptic attacks in animals. Aqueous and alcoholic extracts of Bacopa administered to rats for 15 days significantly reduced mortality due to seizures as well as the intensity of the seizures. (Seizure intensity was measured by increased time of seizure onset. The longer the time of onset, the greater the protective effect of the therapeutic compound.) However, the dose used in these experiments was up to 50% of the LD50 values. The dose was administered intraperitoneally at levels of 600 mg/kg of the aqueous extract and 7000 mg/kg of the alcoholic extract. At the doses used, Bacopa extracts decreased the spontaneous activity of tested animals, but they did not produce a sedative effect or cause uncoordinated movement in the animals.
Another experiment studied the beneficial effects of Brahmi Rasayan on convulsions in mice. When the formula was fed to mice at doses of 1 to 30 gm/kg, it showed a significant protective effect against seizures in animals and significant pain-relieving action, preventing painful stimuli from reaching the brain. The protective effect of the formula was evaluated 30 minutes after its administration. At doses of 10 and 30 gm/kg, Brahmi Rasayan induced sedation in treated animals. Another interesting finding in the second part of this study (using rats) was that the compound at doses 10 and 30 gm/kg was effective in preventing drug (haloperidol)-induced catalepsy. Catalepsy is a serious condition in animals and humans that is characterized by the sudden loss of consciousness, muscle tone, and coordination.
Protection from phenytoin-induced cognitive deficit
The side effects of phenytoin, the commonly used anti-epileptic drug, include impairment of cognitive functions. Bacopa monnieri extract was evaluated for efficacy in reversing this side effect in animal models. Evaluations with regard to passive avoidance response task (PA), maximal electroshock seizures and locomotor activity were performed in mice. The mice received phenytoin (25 mg/kg orally for 14 days). Bacopa monnieri (40 mg/kg for 7 days) given along with phenytoin in the second week of the two-week regimen significantly reversed PHT-induced impairment of cognitive function as determined from the PA results. Both acquisition and retention of memory were improved without affecting the anti-convulsant activity of PHT. These effects were independent of motor stimulation. The authors concluded that Bacopa monnieri has potential use in correcting the cognitive deficit induced by PHT.
Postulated mode of action
It is postulated that the anti-convulsive effects could be mediated through GABA (gamma aminobutyric acid) which is involved in neural impulse transmission because substances that stimulate GABA are known to possess anticonvulsant, pain-relieving and sedative activity.
A more recent study demonstrated the calcium antagonistic activity of an alcoholic extract of Bacopa monnieri on vascular and intestinal smooth muscles of rats and guinea pigs. The plant extract inhibited the spontaneous movements of both guinea pig ileum (IC50: 24 ± 4 μg/ml) and rabbit jejunum (IC50: 136 ± 9 μg/ml). Contractions in the guinea pig ileum induced by acetylcholine were inhibited by the extract at levels of 100-700 μg/ml in a concentration-dependent manner.
These results indicate the direct action of the extract on smooth muscles. The authors also observed that calcium chloride-induced responses in the rabbits’ blood vessels and jejunum were reduced in the presence of the plant extract (10-700 μg/ml), suggesting direct interference with the influx of calcium ions. However, since the extract did not affect contractions induced by noradrenaline or caffeine, the authors concluded that the extract had no appreciable effect on the mobilization of intracellular calcium. Based on the results of the experiment, the authors postulated that the spasmolytic effect of Bacopa monnieri extract in smooth muscles is predominantly due to the inhibition of calcium influx, applicable to both electrical impulse-mediated and receptor-mediated calcium channels in the cell membrane.
One research paper provided an exhaustive summary of the preclinical pharmacological studies on Bacopa monnieri and the isolated bacosides. The cognition facilitating activity of the extract is attributed by saponins, Bacoside A and Bacoside B, which are effective in much lower doses in various model studies, including tests for conditioned taste aversion and conditioned shock avoidance response.