Furthermore, intracellular loading of PKI (6-22) amide, a membrane-impermeable inhibitor of protein kinase A (PKA), into Mauthner cells via whole-cell recording pipettes prevented apomorphine-induced enhancement of VIIIth nerve-Mauthner Dinaciclib order cell synaptic transmission (compare Figure S3D with Figure S3C1), indicating the involvement of postsynaptic PKA in the flash-induced increase of the synaptic efficacy. Behaviorally, the flash-induced enhancement of C-start behavior was prevented by bath

application of SCH-23390 (20 μM; Figure 6G). Bath application of apomorphine (15 μM), which by itself increased the basal C-start probability, occluded the flash-induced enhancement (Figure 6H). Moreover, this occlusion effect

of apomorphine is mediated by D1Rs because the apomorphine-induced increase of basal C-start probability was totally abolished by SCH-23390 application (Figure 6I). Similar effects were also observed when another D1R antagonist SKF-83566 was used (Figure S4). These pharmacological effects on the flash modulation of C-start behavior are consistent with those found for the D1R involvement in the flash enhancement of sound-evoked M-cell responses. Taken together, D1R activation is required for the visual modulation of audiomotor functions at both the neural circuit and behavioral levels. To identify dopaminergic neurons underlying the visual enhancement of sound-evoked C-start behavior and M-cell response, we first examined the effect of specific Fulvestrant ablation of individual dopaminergic neuron clusters in larval zebrafish. Using tyrosine hydroxylase (Th) or DA immunostaining of CYTH4 transgenic ETvmat2:GFP zebrafish larvae, in which monoaminergic neurons express green fluorescent protein (GFP) (Wen et al., 2008), we showed that Th- or DA-positive neurons were located in GFP-expressing nuclei, including the subpallium

(SP), pretectum (PR), preoptic area (PO), ventral thalamus (VT), posterior tubercular (PT), intermediate hypothalamus (HI), and caudal hypothalamus (HC) (Figure S5 and Movies S4 and S5). As these nuclei do not contain Th-expressing noradrenergic neurons (Filippi et al., 2010; Kastenhuber et al., 2010; McLean and Fetcho, 2004a; Yamamoto et al., 2011), Th-positive neurons in these GFP-expressing areas are dopaminergic. Consistent with a previous study (Yamamoto et al., 2011), the HC displayed strong DA-immunoreactivity (-ir; Movie S6) but weak Th-ir because the Th antibody we used preferentially recognized zebrafish Th1 (Yamamoto et al., 2010). Two-photon laser focal lesion of GFP-expressing neurons (Friedrich et al., 2010) in the HC significantly reduced the flash enhancement of sound-evoked C-start behavior (p = 0.