Modulation of dendrodendritic interactions and mitral cell excitability inthe mouse accessory olfactory bulb by vaginocervical stimulation

When female mice are mated, they form a memory to the pheromonal signal of their male partner. The neural changes underlying this memory occur in the accessory olfactory bulb, depend upon vaginocervical stimulation at mating and involve changes at the reciprocal synapses between mitral and granule c ells. However, the action of vaginocervical stimulation on the reciprocal i nteractions between mitral and granule cells remains to be elucidated. We h ave examined the effects of vaginocervical stimulation on paired-pulse depr ession of amygdala-evoked field potentials recorded in the external plexifo rm layer of the accessory olfactory bulb (AOB) and the single-unit activity of mitral cells antidromically stimulated from the amygdala in urethane-an aesthetized female mice. Artificial vaginocervical stimulation reduced pair ed-pulse depression (considered to be due to feedback inhibition of the mit ral cell dendrites from the granule cells via reciprocal dendrodendritic sy napses) recorded in the AOB external plexiform layer. As would be expected from this result, vaginocervical stimulation also enhanced the spontaneous activity of a proportion of the mitral cells tested. These results suggest that vaginocervical stimulation reduces dendrodendritic feedback inhibition to mitral cells and enhances their activity.