ABSTRACT
Essential oil from lovage (Levisticum officinale Koch.) is a potential low-risk insecticide
containing monoterpenes. It was tested with increasing concentrations in saline for neural effects
on the autonomous ventilatory rhythm of an isolated Abdominal Ganglion (AG5) which supplies
the fifth abdominal segment of Locusta migratoria (Forskal). The inhibition by lovage oil was
compared with that of its main components, the enantiomers of limonene (D- and L-limonene). All
substances depressed the persistent ventilatory motor output: the concentration-dependent
reduction of the neural activity was measured with the average Action Potential (AP) frequency
of the inspiratory motoneurons in the median nerve. Occasionally the motor output could switch
from bursting activity with more or less gradual transients to continuous tonic firing. Recovery of
the AG5 in pure saline after highest concentrations had been applied was gradual but the
ventilatory output never returned completely to the pre-application level of motor activity. The
strong short-term neurotoxic effects of the limonene enantiomeres in the insect CNS are followed
by a moderate long term neural depression. |
