Abstract
Baroreceptor regions are definitely present in the arterial wall of the aorta and pulmonary arteries of the domestic fowl. In such regions, the arterial wall is modified by the interruption and absence of the elastic laminae and smooth muscle cells. The baroreceptor endings are similar ultrastructurally to the baro receptors of the mammalian aorta and carotid sinus; therefore they are slowly adapting. Some of the amine- or peptide-containing endings, which are present in the modified regions, share the same Schwann cell with the baroreceptor endings; they probably modulate the stimulus threshold of the baroreceptor endings.