NADPH-diaphorase positive cardiac neurons of the mouse atria: (A) One of the NADPH-diaphorase positive neurons is unipolar (arrow) and the other is bipolar (arrowhead). (B) Note the unipolar NADPH-diaphorase positive neuron (arrow) and the nonreactive neurons (arrowheads). (C) An ovoid bipolar neuron with two short processes (arrow), and one multipolar neuron with three short processes (arrowhead). The neurons are pear-shaped with a round or oval nucleus. (D) A multipolar neuron with three processes. (E) A ganglion stained for NADPH-diaphorase. The ganglion contains both NADPH-diaphorase positive neurons (arrow) and nonreactive perikarya (arrowhead). (F) The two NADPH-diaphorase positive neurons are unipolar neurons. (G) A single NADPH-diaphorase positive neuron with two large processes. (H) Cardiac ganglion showing a cluster of unipolar NADPH-diaphorase positive neurons. Calibration bar: 20 μm.