This review considers the role played by neuropeptides which, unlike GABA and glutamate (acting at ligand-gated ion channels), modulate cardiorespiratory reflexes slowly through metabotropic receptors. Our findings reveal that reflexes may be differentially modulated so that depending on which neuropeptide agonist is microinjected into the rostral ventrolateral medulla, differential effects on reflexes are observed. This means that, for example, the mu opioid agonist DAMGO will attenuate the sympathetic baroreflex but not the somatosympathetic reflex. On the other hand, the delta agonist DPDPE attenuates the somatosympathetic reflex but has no effect on baroreflex function. These, and other data with other peptides, suggest that neuropeptides may play a crucial role in the modulation of different adaptive reflexes.