Calcium Current Diversity in Physiologically Different Local Interneuron Types of the Antennal Lobe

Abstract

Behavioral and physiological studies show that neuronal interactions among the glomeruli in the insect antennal lobe (AL) take place during the processing of odor information. These interactions are mediated by a complex network of inhibitory and excitatory local interneurons (LNs) that restructure the olfactory representation in the AL, thereby regulating the tuning profile of projection neurons. In Periplaneta americana, we characterized two LN types with distinctive physiological properties: (1) type I LNs that generated Na ϩ -driven action potentials on odor stimulation and exhibited GABA-like immunoreactivity (GLIR) and (2) type II LNs, in which odor stimulation evoked depolarizations, but no Na ϩ -driven action potentials (APs). Type II LNs did not express voltage-dependent transient Na ϩ currents and accordingly would not trigger transmitter release by Na ϩ -driven APs. Ninety percent of type II LNs did not exhibit GLIR. The distinct intrinsic firing properties were reflected in functional parameters of their voltage-activated Ca 2ϩ currents (I Ca ). Consistent with graded synaptic release, we found a shift in the voltage for half-maximal activation of I Ca to more hyperpolarized membrane potentials in the type II LNs. These marked physiological differences between the two LN types imply consequences for their computational capacity, synaptic output kinetics, and thus their function in the olfactory circuit.

A 4-dimensional representation of antennal lobe output based on an ensemble of characterized projection neurons

“…However, the error rates of spike sorting depend on many physical, physiological, and other factors and can be rather high (Harris et al, 2000). Furthermore, except in locusts and cockroaches (Laurent and Davidowitz, 1994; Husch et al, 2009), most local interneurons in insect antennal lobes produce sodium spikes (Christensen et al, 1993; Anton and Homberg, 1999; Wilson et al, 2004; Wilson and Laurent, 2005). Moreover, like local interneurons (Christensen et al, 1993), projection neurons can have short stimulus-response latencies (e.g.…”

Competition-Based Model of Pheromone Component Ratio Detection in the Moth

“…While there have been recent advances on Ca 2+ currents in the LNs of the cockroach [39], [40], [41] no complete and detailed voltage clamp data set or existing specific Hodgkin-Huxley models for moth AL LNs has been accessible to us. We, therefore, chose the popular, excitability type 1 Hodgkin-Huxley model neuron of Traub and Miles [22], [23] for the LNs and the PN.…”

Myoinhibitory peptides in the brain of the cockroach Leucophaea maderae and colocalization with pigment‐dispersing factor in circadian pacemaker cells

“…Local interneurons of the antennal lobe are responsible for information processing within and between glomeruli. For a long time it was assumed that local interneurons of the antennal lobes are GABAergic and inhibitory (Homberg and Müller, 1999), but more recent evidence, e.g., from the cockroach P. americana, indicates that different types of local interneurons exist, some of which are not GABAergic (Husch et al, 2009). In addition, various neuropeptides have been detected in small groups of local antennal-lobe interneurons in a variety of insects (Nässel and Homberg, 2006;Carlsson et al, 2010).…”