pyloric dilator nerve (sensu Cancer borealis)

The pyloric dilator nerve (PDN) in Cancer borealis is a peripheral nerve of the stomatogastric nervous system that innervates muscles involved in dilating the valves of the pyloric region of the stomach. It is associated with pyloric dilator neurons, which are electrically coupled with the anterior burster neuron—an intrinsic oscillator—and participate in the pyloric central pattern generator circuit.

In Cancer borealis, the pyloric dilator nerve exits the stomatogastric ganglion and runs to the pyloric region of the stomach. It carries the axons of pyloric dilator (PD) motor neurons to the muscles that open the pyloric valves, which filter the passage of food between the gastric mill and the hindgut.

The pyloric dilator nerve is involved in coordinating the dilation of pyloric valves during the rhythmic filtering movements of the crustacean pyloric stomach. Pyloric dilator neurons, which fire in bursts as part of the pyloric rhythm, inhibit lateral pyloric and pyloric neurons during their burst, helping establish the alternating activity pattern that drives pyloric filtering.

Experimental manipulations including pharmacological application of neuromodulators, photoinactivation of anterior burster neurons, or transection of the stomatogastric nerve may be associated with altered activity in the pyloric dilator nerve. Changes in neuromodulatory tone—such as those associated with temperature changes or starvation—may also be involved in modifying pyloric dilator neuron bursting.

The pyloric dilator nerve is examined using extracellular suction electrode recordings applied to the nerve in semi-intact or fully dissected preparations of the Cancer borealis stomatogastric nervous system. Intracellular recordings identify individual pyloric dilator neuron activity. Immunohistochemistry and dye fills reveal its anatomical trajectory and the neurotransmitter content of the neurons it carries.