Among its many proposed functions, neuropeptide Y (NPY) is thought to
modulate the hypothalamic-pituitary axis. Specifically, increased hypo
thalamic NPY signaling may be critical in mediating the neuroendocrine
response to fasting. To determine the consequences of NPY deficiency
on endocrine physiology, multiple hormones were quantitated in wildtyp
e and NPY-knockout mice under fed and fasted conditions. Serum concent
rations of leptin, corticosterone, thyroxine, and testosterone were no
rmal in NPY-knockout males fed ad libitum. A 48-hour fast resulted in
a 50% reduction in leptin, a 60% reduction in thyroxine, a 75% reducti
on in testosterone, and a 12-fold increase in corticosterone in both w
ildtype and NPY-knockout mice. Fasting also increased the estrous cycl
e length by 3 days in both wildtype and NPY-deficient female mice. We
conclude that NPY is not essential for appropriate function of the gon
adotropic, thyrotropic, or corticotropic axes under ad lib fed conditi
ons or in response to acute fasting. (C) 1997 Elsevier Science B.V.