P-32 Correlating Neural and Behavioral Responses in an Insect Model and the Effect of Neuromodulators in Cricket Phonotaxis

Phonotaxis in female cricket Acheta domesticus can be selective or unselective in response to model calls with varying syllable periods. Discriminating a model call and walking towards it implies that a certain network(s) of neurons is/are activated when the call is recognized as attractive. Several approaches to demonstrate the influential role of auditory neurons in phonotaxis have been used with different levels of success. One such approach (current study) seeks to evaluate the behavioral and neuronal responses in the same animal, using identical auditory stimuli. This approach allows us to establish a correlation between the neuronal and behavioral responses, as well as to predict the behavior of the animal based on the response of the neuron. The L3 prothoracic auditory neuron has been suggested to influence syllable period selective phonotaxis in this species. In response to calls with attractive syllable periods, the L3 produces a burst of action potentials, which diminish in response to consecutive syllables. Such a decrease in the number of action potentials calculated as percentage is called decrement. Preliminary results indicate that syllable periods that produce positive phonotaxis, also elicit higher decrement values in the neuronal response of the same animal. In the lab, young (5-10 days), virgin females are more likely to respond phonotactically to calls with syllable period ranging between 50 and 70 ms. Older, virgin females (greater than 20 days), exhibit more variability in the range and number of syllable periods they respond to, which may or may not overlap with the range indicated for young ones. Neuromodulators such as juvenile hormone III (JHIII) have been shown to modify phonotactic selectivity. The effect other neurochemicals may have on cricket phonotaxis remains to be evaluated. Octopamine has been shown to increase aggressive behavior in crickets. Preliminary prothoracic nanoinjections of octopamine show decreased phonotactic responsiveness in young females. A second neuromodulator, chelerythrine chloride (CC), a protein kinase C (PKC) blocker is believed to be part of the signaling mechanism in crickets, particularly regarding JHIII pathway. When older females are nanoinjected with JHIII, selectivity increases. When CC is nanoinjected in young females, selectivity decreases. We hypothesize that older female crickets which are more likely to be unselective, will show little or no change in selectivity following CC injection. This exploratory component of the current study seeks to identify neurochemicals which may be of importance in modulating cricket’s phonotactic behavior.