Agonists of the incretin GLP-1 have been found to have a sedative or anxiolytic effect on the mammalian central nervous system. Additionally, exendin has been found to have an independent sedative effect on the mammalian central nervous system. Conversely, antagonists of GLP-1 increase nervous system activity. The invention relates, in one aspect, to the use of GLP-1 agonists and antagonists to affect the arousal state of the mammalian central nervous system. The invention also relates to novel transgenic mammals in which the GLP-1 receptor gene has been disrupted.