Distribution and projections of cholecystokinin-immunoreactive neurons in the hypothalamic paraventricular nucleus of rat.
Analysis of coronal sections from colchicine-treated rat brains reveals that CCK-immunoreactivity (CCK-ir) is present in two distinguishable neuronal systems in the paraventricular nucleus (PVN). More than 60% of these cells were found to be typical parvicellular neurons; the remainder were magnocellular neurons. The magnocellular CCK-ir neurons were concentrated in the medial magnocellular subdivision, while more caudally they formed a ring around a zone of unstained magnocellular neurons. Immunostained parvicellular neurons predominate in medial and periventricular parvicellular subdivisions. The efferent projections of CCK-ir neurons were investigated by looking for retrograde accumulation of CCK-ir in cell bodies after selective knife cuts. A parasagittal cut of the lateral retrochiasmatic area as well as transection of the rostral median eminence resulted in an accumulation of CCK-ir material in a large number of both parvi- and magnocellular neurons. After pituitary stalk lesions, however, increased staining was only seen in magnocellular neurons. It is inferred that the magnocellular (presumed oxytocin-CCK) cells send their axons to the pituitary, whereas axons of CCK-ir parvicellular neurons appear to terminate in the median eminence. After transection of the medial forebrain bundle (MFB), immunostaining increased in a small number of scattered transected fibers proximal to the knife cut and in a few perikarya in the PVN, indicating that very few CCK cells may send descending fibers to the lower brainstem.
D000818:Animals; D001931:Brain Mapping; D001933:Brain Stem / Q000033:anatomy & histology; D002766:Cholecystokinin / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D008474:Medial Forebrain Bundle / Q000033:anatomy & histology; D008473:Median Eminence / Q000033:anatomy & histology; D009434:Neural Pathways / Q000033:anatomy & histology; D010286:Paraventricular Hypothalamic Nucleus / Q000033:anatomy & histology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D002766:Cholecystokinin