Effects of Passiflora incarnata L. on rat hippocampal G protein-coupled receptors (GPCRs)

Abstract

Passiflora has potential effects for treatment of some diseases like anxiety, insomnia, attention-deficit hyperactivity disorder, cancer, and may be helpful in the treatment of substance addictions [1], [2]. However, very few pharmacological studies have been undertaken on the activity of P. incarnata; most of these investigations have been carried out with different Passiflora species, such as P. edulis, P. alata, or P. coerulea and with insufficient phytochemical characterization of the extracts. The goal of the present study was to search for possible new targets of the extract contained as active ingredient in the herbal drug Pascoflair® 425mg on rat hippocampal GPCRs. The following agonists evoked an increased [35S]-GTP? S signal and it can therefore be concluded that the respective receptors are present in the membrane preparation (in brackets): acetylcholine (muscarinic M2 or M4), DAGO (µ-opioid), ADP (P2Y12 or P2Y13), HU-210 (cannabinoid CB1 > CB2), CCPA (adenosine A1), serotonin (serotonin 5-HT1all subtypes) and glutamate (metabotropic glutamate receptors, mGlu2,3,4,6,7,8). An antagonistic effect of Passiflora on Hu-210 and CCPA-evoked [35S]-GTP? S binding was observed. No other agonistic/antagonistic action of Passiflora could be detected. Thus, our findings suggest that the Passiflora extract is an antagonist of the adenosine A1 and the cannabinoid receptors. This would be consistent with the observed effects of Passiflora, because adenosine A1 receptor antagonists display anxiolytic activity [3] and cannabinoid receptor antagonist have therapeutic effects for the treatment of substance dependence [4].