Question

6. Forskolin is a drug that affects adenylyl cyclase in a similar manner as GPCRs coupled to Gαs. What effect do you expect on the siphon-poke-induced gill withdrawal behavior if you applied this drug to an Aplysia prep ?

Answer 1

Aplysia is a sea slug. When an external stimuli touches on the siphon of Aplysia, its gill muscles contract immediately and gets retracted into the mantle cavity of the organism. This behavior is performed by the sensory neurons in the siphon and motor neurons in the gill muscle. The neurons that mediate the Aplysia sensitization are called facilitator neurons. The effect of facilitator neuron stimulation is mediated by cAMP (cyclic adenosine monophosphate) and a cAMP dependent protein kinase. Adenylyl cyclase is an enzyme that convert ATP (adenosine triphosphate) into cAMP. So for an elevated cAMP level, adenylyl cyclase is required.

ATP ----------------------(adenylyl cyclase)---------------------> cAMP

Forskolin is a tool used to raise the levels of cyclic AMP (cAMP), by activating the enzyme adenylyl cyclase. So if we apply forskolin to an aplysia prep, it will facilitate the siphon-poke-induced gill withdrawal behavior by enhancing the production of adenylyl cyclase and so cAMP.