 Vagal afferent C fibers originating in the heart and lungs terminate in the NTS, while axons from the heart also inhibit sympathetic nervous activity "via" the caudal ventrolateral medulla (CVLM) and possibly the rostral ventrolateral medulla (RVLM).The sites of the chemoreflex and baroreflex input overlap and there is evidence that these reflexes modify each other, probably through the actions of excitatory and inhibitory neurotransmitters, such as serotonin and  Gamma-Aminobutyric acid (GABA).Although the reflex was originally described in response to Veratrum alkaloids, it can be stimulated by many biologically active chemicals, including nicotine, capsaicin, bradykinin, atrial natriuretic peptide, prostanoids, nitrovasodilators, angiotensin II type 1 receptor (AT1) antagonists and serotonin agonists.