Anum Qassam   Cornell University College Of Engineering

The Pyloric Circuit 


The entirety of the STG has only 30 cell bodies, and 14 of these cells are located in the pyloric circuit. Each of these cells is then categorized into six broad categories: Anterior burster (AB), Pyloric dilator (PD), Pyloric (PY), Inferior cardiac (IC), Ventricular dilator (VD), and Lateral pyloric (LP).  The AB is the “pacemaker”– it is the only tonically bursting cell in the circuit. That is, it will continue producing action potentials without any sensory or synaptic input. In the event that all the neurons are oscillating in the circuit, it is the AB cell that has the fastest oscillation, pushing the other neurons to its frequency. The PD cell controls the cardiopyloric valve, and is a pacemaker by virtue of its electrical synapse with the AB cell. The VD and IC cells control the ventral stomach grooves. Finally the 8 PY cells and the LP cell controls pyloric filter movements.

In the following explanation of the mechanism of the pyloric circuit, refer to the circuit diagram below:


Initially, the AB cell, which is phasically bursting, forces the electrically coupled PD cells into synchrony.  Note that the PD cells are tonically active, and only display the bursting pattern due to the electric coupling with the AB cell. These three cells inhibit the 8 PY cells, causing them to fire out of sync (these cells can only fire when the AB and PD cells are not inhibiting them, that is to say when they are inactive).  The VD, LP, and IC cells are rebound spikers, so they spike as a result of a strong inhibition. Each of these cells then has inhibiting interactions with other cells in the circuit, causing the specific voltage patterns shown below.

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