LOCAL INHIBITION OF NITRIC-OXIDE SYNTHASE ACTIVITY IN THE ACCESSORY OLFACTORY-BULB DOES NOT PREVENT THE FORMATION OF AN OLFACTORY MEMORY INMICE

The putative intercellular transmitter nitric oxide has been suggested to play a role in synaptic plasticity in several models of learning a nd memory. We have investigated the cellular localisation of nitric ox ide synthase in the accessory olfactory bulb of the mouse, using immun ohistochemistry and NADPH diaphorase histochemistry. The strikingly hi gh levels of nitric oxide synthase observed in the accessory olfactory bulb were found to be due almost exclusively to its localisation in g ranule cell interneurons. In mice the accessory olfactory bulb has bee n proposed as the site of synaptic changes occurring during the format ion of an olfactory memory to male pheromones. In an attempt to disrup t the formation of this olfactory memory, we used local infusions of t he nitric oxide synthase inhibitor L-N(G)-nitroarginine, into the olfa ctory bulb over the critical period for memory formation. Infusions Of L-N(G)-nitroarginine at doses that effectively inhibited nitric oxide synthase activity did not prevent memory formation. The apparent resi stance of this memory to inhibition of nitric oxide synthase activity may reflect the special nature of the mitral cell to granule cell reci procal synapse in the accessory olfactory bulb.