Veterinary/zoology session

Ecto-nucleoside triphosphate diphosphohydrolase 3 (NTPDase3) has been described as a plasma membrane-incorporated enzyme hydrolyzing ATP and ADP outside of the cell. The localization of NTPDase3 in the rat brain implies a role for this enzyme in the hypothalamic regulation of various homeostatic systems, such as food-intake, sleep-wake behavior and reproduction. The main goal of the present study was to identify and characterize the NTPDase3-immunoreactive (NTPDase3-IR) neural structures and to determine the possible cellular role(s) of NTPDase3 in hypothalamic neurons. Correlated light- and electron microscopic analysis of immunostained hypothalamic slices indicated that besides the plasma membrane, NTPDase3 is also expressed in the perikaryal cytoplasm, axons and dendrites of hypothalamic neurons. Perikaryal NTPDase3-IR was linked to ribosomes, mitochondria and distinct segments of the plasma membrane. NTPDase3-IR mitochondria were detected in non-GABAergic neurons, near asymmetric synapses, suggesting that this enzyme may play a role in excitatory neurotransmission. The occurance of membrane-incorporated NTPDase3 at non-synaptic membrane sites indicates that it likely plays a role in paracrine intercellular signaling and/or in the convenience of peripheral humoral signals in the hypothalamus.