TY - JOUR
T1 - Melanocortin 4 receptor-mediated hyperphagia and activation of neuropeptide Y expression in the dorsomedial hypothalamus during lactation
AU - Chen, Peilin
AU - Williams, Sarah M.
AU - Grove, Kevin L.
AU - Smith, M. Susan
PY - 2004/6/2
Y1 - 2004/6/2
N2 - In several hyperphagic models, including lactation, in which hypothalamic melanocortin signaling is reduced, a novel expression of NPY mRNA in the dorsomedial hypothalamus (DMH) has been observed, suggesting that melanocortin signaling and the induced NPY in the DMH may constitute unique neurocircuitry in mediating energy balance. Using lactating rats as a model, the present study first showed that in the DMH abundant α-MSH and agouti-related protein fibers are in close apposition to NPY-positive cells. However, no NPY and MC4R (a melanocortin receptor) double-labeled neurons were observed. These data suggested that melanocortin input may synapse on presynaptic terminals that then synapse on DMH NPY cells. To study the function of DMH MC4Rs in energy balance, an MC3/4R-selective agonist, melanotan II (MTII), was injected bilaterally into the DMH. MTII injection significantly suppressed feeding induced by 24 hr fasting or suckling-induced hyperphagia. Furthermore, MTII treatment greatly attenuated suckling-induced NPY expression in the DMH. MTII treatment also stimulated uncoupling protein 1 activity in the brown adipose tissue of suckling female rats, indicative of increased sympathetic outflow. In summary, the present study demonstrated that the melanocortin system in the DMH not only plays an important role in inducing NPY expression in the DMH of lactating rats but also in regulating energy homeostasis, at least in part, by modulating appetite and energy expenditure.
AB - In several hyperphagic models, including lactation, in which hypothalamic melanocortin signaling is reduced, a novel expression of NPY mRNA in the dorsomedial hypothalamus (DMH) has been observed, suggesting that melanocortin signaling and the induced NPY in the DMH may constitute unique neurocircuitry in mediating energy balance. Using lactating rats as a model, the present study first showed that in the DMH abundant α-MSH and agouti-related protein fibers are in close apposition to NPY-positive cells. However, no NPY and MC4R (a melanocortin receptor) double-labeled neurons were observed. These data suggested that melanocortin input may synapse on presynaptic terminals that then synapse on DMH NPY cells. To study the function of DMH MC4Rs in energy balance, an MC3/4R-selective agonist, melanotan II (MTII), was injected bilaterally into the DMH. MTII injection significantly suppressed feeding induced by 24 hr fasting or suckling-induced hyperphagia. Furthermore, MTII treatment greatly attenuated suckling-induced NPY expression in the DMH. MTII treatment also stimulated uncoupling protein 1 activity in the brown adipose tissue of suckling female rats, indicative of increased sympathetic outflow. In summary, the present study demonstrated that the melanocortin system in the DMH not only plays an important role in inducing NPY expression in the DMH of lactating rats but also in regulating energy homeostasis, at least in part, by modulating appetite and energy expenditure.
KW - Dorsomedial hypothalamus
KW - Food intake
KW - Lactation
KW - MC4R
KW - NPY
KW - UCP1
UR - http://www.scopus.com/inward/record.url?scp=2642576000&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=2642576000&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.0588-04.2004
DO - 10.1523/JNEUROSCI.0588-04.2004
M3 - Article
C2 - 15175378
AN - SCOPUS:2642576000
SN - 0270-6474
VL - 24
SP - 5091
EP - 5100
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 22
ER -