In vivo control of olfactory receptor neuron input to the olfactory bulb by presynaptic inhibition

PÍREZ, N.; WACHOWIAK, M.

Colonia del Sacramento

Conferencia; First Latin American Meeting of Chemical Ecology; 2010

Latin American Association of Chemical Ecology

The first major reorganization of odor representations in the nervous system occurs at the synapse between olfactory receptor neurons and second-order neurons in the olfactory bulb. Signal transmission at this synapse is modulated by signaling pathways that regulate the amount of transmitter release from the receptor neuron, controlling the strength of sensory input to the brain. Using in vivo calcium imaging, we imaged from the receptor neuron terminals of anesthetized mice before and after blocking GABA-ergic presynaptic inhibition and investigated what features of neural activity control the strength of this inhibition. As expected from earlier studies, blocking presynaptic GABAB receptors in vivo increased odorant-evoked presynaptic calcium signals, confirming that GABAB-mediated inhibition modulates the strength of receptor inputs. We found that the strength of this inhibition was affected little by the nature of the input, being independent of the spatial distribution of activated glomeruli, independent of the sniff frequency used to sample the odorant, and similar for weak and strong odorant-evoked inputs. Instead, we found that tonic inhibition was a major determinant of receptor input strength. This finding establishes a neural substrate by which the strength of sensory input to the brain may be modulated as a function of behavioral state. Funded by NIH DC06441.