The essential oil of Croton nepetaefolius selectively blocks histamine-augmented neuronal excitability in guinea-pig celiac ganglion

Abstract

Abstract Objectives Croton nepetaefolius is a medicinal plant useful against intestinal disorders. In this study, we elucidate the effects of its essential oil (EOCN) on sympathetic neurons, with emphasis on the interaction of EOCN- and histamine-induced effects. Methods The effects of EOCN and histamine were studied in guinea-pig celiac ganglion in vitro. Key findings Histamine significantly altered the resting potential (Em) and the input resistance (Ri) of phasic neurons (from −56.6 ± 1.78 mV and 88.6 ± 11.43 MΩ, to −52.9 ± 1.96 mV and 108.6 ± 11.00 MΩ, respectively). Em, Ri and the histamine-induced alterations of these parameters were not affected by 200 µg/ml EOCN. The number of action potentials produced by a 1-s (two-times threshold) depolarising current and the current threshold (Ith) for eliciting action potentials (rheobase) were evaluated. Number of action potentials and Ith were altered by histamine (from 2.6 ± 0.43 action potentials and 105.4 ± 11.15 pA to 6.2 ± 1.16 action potentials and 67.3 ± 8.21 pA, respectively). EOCN alone did not affect number of action potentials and Ith but it fully blocked the histamine-induced modifications of number of action potentials and Ith. All the effects produced by histamine were abolished by pyrilamine. Conclusions EOCN selectively blocked histamine-induced modulation of active membrane properties.