L9 modulation of L7's elicited gill withdrawal response in Aplysia.

The effects of induced L9 activity on gill motor neuron L7's ability to elicit a gill withdrawal response were studied. It was found that L9 was a modulator of L7's effectiveness to elicit gill movements. Following L9 activity, L7's ability to elicit a gill withdrawal response was significantly potentiated by up to 240% of control. L9 activity potentiated L7's elicited gill withdrawal response when frequencies of L7 activity were used which would result in decrement of the response or when frequencies were used in which decrement does not occur. Induced L9 activity may also have a minor potentiating effect on LDG1's ability to elicit gill movements. L9 was the only neuron found to possess these modulatory abilities. The interposition of the activity in the other gill motor neurons failed to have any effect. L9's modulatory role is separate and independent from its role as a gill motor neuron. L9's modulation of L7 is mediated peripherally in the gill and not in the CNS.