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

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 (E m ) and the input resistance (R i ) of phasic neurons (from −56.6 ± 1.78 mV and 88.6 ± 11.43 M Ω , to −52.9 ± 1.96 mV and 108.6 ± 11.00 M Ω , respectively). E m , R i and the histamine‐induced alterations of these parameters were not affected by 200  µ g/ml EOCN. The number of action potentials produced by a 1‐s (two‐times threshold) depolarising current and the current threshold (I th ) for eliciting action potentials (rheobase) were evaluated. Number of action potentials and I th 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 I th but it fully blocked the histamine‐induced modifications of number of action potentials and I th . All the effects produced by histamine were abolished by pyrilamine. Conclusions  EOCN selectively blocked histamine‐induced modulation of active membrane properties.