Paper: Diversity and wiring variability of olfactory local interneurons in the Drosophila antennal lobe (Ya-Hui Chou, 2010)
Neurons can be divided into two general categories: projections neurons, whose axons connect discrete regions of neural tissue, and local interneurons, whose processes are restricted to a single region.
All olfactory receptor neurons (ORNs) that express the same odorant receptor project their axons to the same antennal lobe glomerulus, and most antennal lobe projection neurons (PNs) send dendrites into a single glomerulus to receive direct input from one ORN class.
as a general rule, LNs broadcast transmitter release across their arborization without notable glomerular selectivity
we found a significant positive correlation between LN innervation probability and mean odor-evoked ORN firing rate. This would be consistent with the idea that the density of inhibitory innervation is adapted to the average level of afferent input to each glomerulus, assuming that these stimuli are representative of natural odors.
innervation patterns are not well described as the linear combination of any small number of basic glomerular relationships
a defining feature of an LN’s innervation pattern is the number of glomeruli it connects to
during the construction of the antennal lobe circuit, PN dendrites initiate pattern formation before the arrival of pioneering axons by targeting dendrites to positions similar to those where they are found in the adult antennal lobe. ORN axon invasion into the antennal lobe and subsequent ORN axon – PN dendrite recognition results in the formation of distinguishable glomeruli.
Panglomerular LNs had unusually high rates of spontaneous activity, suggesting that they may be particularly important in broadcasting tonic inhibition throughout the antennal lobe
Panglomerular LNs either were inhibited by odors or were only weakly excited
- LNs in Drosophila are more complex than previously expected
- Most LNs innervate glomeruli without selectivity (panglomeruli)
- inhibitory density is adapted to the average level of afferent input to each glomeurlus
Paper 2: Plasticity of local GABAergic interneurons drives olfactory habituation
habituation arises from potentiation of inhibitory transmission within a circuit motif commonly repeated in the nervous system
habituation arises from glomerulus-selective potentiation of inhibitory synapses in the antennal lobe
STH can be induced without receptor activation and thus, cannot be explained by adaptation of the odorant-receptor signaling pathway
the observed requirement for rut in LNs suggests that behavioral habituation arises from rut-dependent strengthening of GABAergic LN1 synapses in the antennal lobe
LTH is accompanied by a selective reduction of PN responses to the habituated odor
synaptic output from LN1 neurons is necessary for display of STH. … transmitter release from LN1 neurons was necessary during the exposure period
knockdown of GABAA receptors in defined subsets of PNs selectively blocked habituation to their respective odorants without affecting the basal olfactory response
transmitter release from LN1 neurons is necessary, and the potentiation of LN1 activity is sufficient for the attenuated behavioral response observed in habituation