GABAA Receptor RDL Inhibits Drosophila Olfactory Associative Learning

Abstract

In both mammals and insects, neurons involved in learning are strongly modulated by the inhibitory neurotransmitter GABA. The GABAA receptor, resistance to dieldrin (Rdl), is highly expressed in the Drosophila mushroom bodies (MBs), a group of neurons playing essential roles in insect olfactory learning. Flies with increased or decreased expression of Rdl in the MBs were generated. Olfactory associative learning tests showed that Rdl overexpression impaired memory acquisition but not memory stability. This learning defect was due to disrupting the physiological state of the adult MB neurons rather than causing developmental abnormalities. Remarkably, Rdl knockdown enhanced memory acquisition but not memory stability. Functional cellular imaging experiments showed that Rdl overexpression abolished the normal calcium responses of the MBs to odors while Rdl knockdown increased these responses. Together, these data suggest that RDL negatively modulates olfactory associative learning, possibly by gating the input of olfactory information into the MBs.

Plasticity of Recurrent Inhibition in theDrosophilaAntennal Lobe

“…3A). Knockdown of GABA A receptors by targeted expression of a UAS-RdlRNAi construct (Liu et al, 2007(Liu et al, , 2009; Das et al, 2011) in PNs expressing TRPA1 also similarly blocked habituation induced by exposure to 29°C for 30 min (Fig. 3B).…”

A GABAergic Inhibitory Neural Circuit Regulates Visual Reversal Learning inDrosophila

“…Previous reports have shown that downregulation of GABA synthesis in the APL neurons led to enhanced olfactory associative learning in the T-maze paradigm (Liu and Davis, 2009), the same behavioral phenotype produced by knocking down GABA A receptor RDL in the MBs (Liu et al, 2007). Heat punishment was associated with upright T but switched to inverted T upon reversal of stimulus-reinforcement association.…”

“…Flies were reared in standard food vials at 25°C and 60% relative humidity with a 12 h light/dark cycle (Guo et al, 1996). The upstream activating sequence (UAS) strain Rdli8 -10j (Liu et al, 2007) was provided by Dr. R. Davis (The Scripps Research Institute, Jupiter, FL) and the GH146-Gal4 (Stocker et al, 1997) and UAS-TNTE (Sweeney et al, 1995) strains by Z.R. Wang (Institute of Neuroscience, Chinese Academy of Sciences).…”

“…After three 20 min washings in PBS containing 0.3% Triton X-100 (PBT), the brains were blocked with 5% normal goat serum (Invitrogen 01-6201) in PBT for an hour. Brains were then incubated with primary antibodies in blocking solution at 4°C for 48 h. After six 20 min washings in PBT, samples are incubated with secondary antibodies at 4°C for 12 h. The primary antibodies used include: rabbit anti-RDL (1:100; kindly provided by Dr. R. Davis, The Scripps Institute, Jupiter, FL) (Liu et al, 2007), mouse anti-FasII (1:50; Developmental Studies Hybridoma Bank 1D4), rabbit anti-GABA (1:50; Sigma A2052), mouse anti-green fluorescent protein (GFP) (1:100; Invitrogen A11120), mouse anti-nc82 (1:40; Developmental Studies Hybridoma Bank ), and rabbit anti-GFP (1:100; Sigma A6455). Secondary antibodies (1:500; Invitrogen) include: Alexa 488 goat anti-rabbit IgG (A11008), Alexa 488 goat anti-mouse IgG (A11001), Alexa 568 goat anti-rabbit IgG (A11011), Alexa 633 goat antimouse IgG (A21053), and Alexa 633 goat anti-rabbit IgG (A21070).…”

Seizure Sensitivity Is Ameliorated by Targeted Expression of K+–Cl− Cotransporter Function in the Mushroom Body of the Drosophila Brain

“…The kcc DHS1 stock carrying OK107 (D642) was constructed by first crossing D245 virgin females to a w;;;OK107 stock, then crossing w; 1/ CyO;;OK107/1 male progeny from this cross to homozygous w; kcc DHS1 D506 virgin females and finally combining w; kcc DHS1 / CyO;;OK107/1 male and virgin female progeny from this cross to establish a stock. The MB-GAL80 flies were from Scott Waddell (University of Massachusetts Medical School); flies carrying the Ncc69 RNAi (Dietzl et al 2007) and Rdl RNAi (Liu et al 2007) were obtained from the Bloomington Drosophila Stock Center. Strains carrying kcc DHS1 along with one of these third chromosomal mutations were created as in the same manner as described for the third chromosomal GAL4 driver stocks.…”