Cholinergic neurons mediate CaMKII-dependent enhancement of courtship suppression

Abstract

In Drosophila, calcium/calmodulin-dependent protein kinase II (CaMKII) activity is crucial in associative courtship conditioning for both memory formation and suppression of courtship during training with a mated female. We have previously shown that increasing levels of constitutively active CaMKII, but not calcium-dependent CaMKII, in a subset of neurons can decrease the initial level of courtship and enhance the rate of suppression of courtship in response to a mated female. In this study, we demonstrate that a subpopulation of noncholinergic, nondopaminergic, non-GABAergic neurons can cause CaMKII-dependent reductions in initial courtship, but only cholinergic neurons enhance training-dependent suppression. These data suggest that processing of pheromonal signals in two subpopulations of neurons, likely antennal lobe projection neurons, is critical for behavioral plasticity.Modification of behavior on short time scales requires fast, likely cell signaling, changes in neuronal circuits. One molecule that has been shown in many systems to be responsible for both short-term and long-term changes in neuronal activity is calcium/calmodulin-dependent protein kinase II (CaMKII). This kinase can act a molecular switch, becoming calcium independent after autophosphorylation at T287. Production of constitutively active kinase is believed to be a first step toward establishing short-and long-term changes in neuronal properties that underlie learning (for review, see Lisman et al. 2002).In Drosophila courtship conditioning, CaMKII is important for behavioral changes that occur during the training period and for formation of associative memory (Griffith et al. 1993; Griffith 1997, 1999). In this behavioral paradigm, a male is exposed to a previously mated female for 1 h, and the effects of training are assessed by measuring courtship of a subsequently presented virgin female. Naive males exposed to virgin females sense female-specific stimulatory pheromones and rapidly initiate courtship, usually copulating within 15 min. In comparison, trained males show reduced courtship of virgins, and this is believed to be the result of association of stimulatory pheromones with an aversive substance given off by mated females (Tompkins et al. 1983). Memory formation can be blocked by inhibition of CaMKII in mushroom bodies, central complex, and parts of the lateral protocerebrum (Joiner and Griffith 1999). The behavior of males during training is also plastic; they initiate vigorous courtship, but over the course of training they decrease their intensity of courtship and rarely copulate. The suppression of courtship during training is driven by a neuronal circuit distinct from that mediating associative memory formation, involving neurons in the antennal lobes and lateral protocerebrum (Joiner and Griffith 1999).The requirement for CaMKII activity was determined using spatially restricted expression of a peptide, which inhibits both the calcium-dependent and the calcium-independent (autophosphorylated at T287) forms of the kinase. ...

Presynaptic LRP4 promotes synapse number and function of excitatory CNS neurons

“…To test this, we used Brp-Short to examine synapse number in GABAergic inhibitory neurons projecting to the antennal lobe using the GAD1-GAL4 driver (Ng et al, 2002). Though GAD1-positive neurons project throughout the antennal lobe (Mehren and Griffith, 2006), we restricted our analyses to the DA1 glomerulus, where we observed reductions in excitatory synapses (Figure 2—figure supplements 3–4) following LRP4 disruption. When LRP4 function was impaired using the lrp4 dalek mutant or RNAi in these neurons, synapse number was unaffected (Figure 4A–B,D).…”

Roles of Calcium/Calmodulin-Dependent Kinase II in Long-Term Memory Formation in Crickets

“…In courtship conditioning in fruit-flies, constitutively activated CaMKII in cholinergic neurons of the antennal lobe plays roles in behavioral change during training [16], [43], and CaMKII in neurons of the lateral protocerebrum or the central complex plays roles in acquisition of memory [15]. In olfactory learning in fruit-flies, it has been reported that CREB-dependent transcription and translation of CaMKII proteins in Kenyon cells of the mushroom body [19], [20] or dorsal-anterior-lateral (DAL) neurons [44] are necessary for LTM formation.…”

Thermosensory processing in the Drosophila brain

“…Gad1-Gal4 (line 2B) was constructed by Toshi Kitamoto using a Gad1 promoter fragment and was first published in ref. 26 , where it was called “ Gad2B-Gal4 ”. Gr28b MB03888 was reported in ref.…”

“…We therefore targeted our electrodes to this cluster when we used a Gad1-Gal4 line 26 to drive CD8::GFP expression in putative GABAergic neurons. In order to determine if the CD8::GFP-expressing somata in this cluster are indeed GABAergic, we performed dual immunofluorescence confocal microscopy with anti-CD8 and anti-GABA antibodies.…”