Central, but not peripheral application of motilin increases c-Fos expression in hypothalamic nuclei in the rat brain.
Previous immunocytochemical studies have shown the presence of motilin-immunoreactive neurons in specific brain areas of rats and autoradiographic studies in rabbits demonstrated motilin-binding sites in the central nervous system as well. Therefore, the aim of this study was to determine the anatomical localisation and neurochemical features of neurons activated by central administration of motilin (Mo) in rats. One week after cannulation, an intracerebroventricular injection of Mo (ICV, 3 microg/6 mul 0.9% saline) was given. For comparative purposes, a group of animals received an intravenous injection of motilin (IV, 9 microg/300 mul 0.9% saline) or an equal volume of saline. Neuronal excitation was assessed by c-Fos immunocytochemistry and combined with immunostaining for neurotransmitter markers. In contrast to the IV motilin-treated animals, the ICV motilin-treated animals displayed a significant increase in c-Fos expression in the supraoptic nuclei (SO) and paraventricular nuclei of the hypothalamus (PVH). At the level of the dorsomedial, ventromedial and lateral hypothalamic nuclei, ICV administration of motilin did not induce changes in c-Fos expression. In addition, the cerebellum did not show c-Fos expression after ICV motilin administration either. These findings might suggest distinct pathways and actions of centrally released and systemic motilin, but, particularly in rodents, do not rule out the possibility that the effects seen in the SO and PVH after ICV application are aspecific in nature. At present, we cannot exclude the fact that the results observed with motilin in rodents are due to cross-interaction with other related (e.g. ghrelin) or not yet identified receptors.
Wu
Mei
M
Medical College, University of Qingdao, 38 Dengzhou Road, 266021 Qingdao, People's Republic of China.
Tang
Ming
M
Adriaensen
Dirk
D
Depoortere
Inge
I
Peeters
Theo L
TL
Timmermans
Jean-Pierre
JP
D000818:Animals; D005260:Female; D005765:Gastrointestinal Agents / Q000494:pharmacology; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007150:Immunohistochemistry; D007275:Injections, Intravenous; D007276:Injections, Intraventricular; D008297:Male; D009037:Motilin / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D005765:Gastrointestinal Agents; D016760:Proto-Oncogene Proteins c-fos; D009037:Motilin