PROPERTIES OF NADPHD-POSITIVE NEURONS IN HELIX BRAIN

Studies of NADPH-diaphorase (NADPHd) histochemistry in Helix brain ind icate a number of discrete populations of putative NO-producing neuron s in different ganglia, It has been shown that NADPHd-positive neurons (4 populations) have similar morphological, electrical, and plastic p roperties, These neurons are small (about 20 mcm), silent, with low th reshold of excitability and low synaptic activity, They don't habituat e to stimulation by impulses of depolarizing current and demonstrate l ow sensitivity; to neurotransmitters, Serotonin, dopamine, and opiod p eptides hyperpolarize, and glumamate, NMBA, and acetylcholine depolari ze them, The evidence has been obtained that NO regulates: the electri cal and plastic properties of NADPHd-positive neurons in Helix brain a nd potentiate's their sensitivity to glutamate, The properties of puta tive NO-producing Helix neurons have been compared with the known prop erties of vertebrate NO-producing neurons, The possible mechanisms are discussed of regulation by NO of the plastic properties of these neur ons.