Figure 1.

A, Behavioral procedure: rats were trained to associate one context with access to sucrose and another context with access to salt (4 d in each context, 20 min per session). Rats were then given a baseline test in which they were allowed access to both contexts for the first time in the absence of sucrose or salt (flavored solutions still present). After 4 d of retraining (2 d in each context), rats were sodium-depleted with furosemide (10 mg/kg, i.p.). After 48 h, rats were given a depletion test identical to the baseline test except that now rats received yellow laser stimulation (3 s on, 3 s off train). Finally, rats were given a consumption test identical to the depletion test but now sucrose and salt were available in each solution. B, Representative brain slice from a Halo rat showing eNpHR3.0-EYFP expression in the VP and fiber track. ac, Anterior commissure. C–E, Example of eNpHR3.0-EYFP, Neurotrace, and coexpression of each from a brain slice of a rat that received AAV5-hSyn-eNpHR3.0-EYFP infusions in the VP. F–H, Example of EYFP, Neurotrace, and coexpression of each from a brain slice of a rat that received AAV5-hSyn-EYFP infusions in the VP. I, Schematic diagram of eNpHR3.0-EYFP expression in the VP (shading overlay) and fiber implant placements (squares) from all Halo rats (n = 12). Numbers on the left are number of millimeters from bregma. Illustrations adapted from Paxinos and Watson (2009). J, Schematic diagram of eNpHR3.0-EYFP expression in the VP (shading overlay) and fiber implant placements (squares) from all rats classified as Misses (n = 5). Note that three placements are not mapped due to either the fiber placement being too anterior and not above or within the VP (beyond 0.36 mm from bregma; n = 2) or the fiber placement was unable to be located (n = 1). Numbers on the left are number of millimeters from bregma. Illustrations adapted from Paxinos and Watson (2009).