Mice were anaesthetised with isoflurane (3% induction, 0.5–1% maintenance), treated with buprenorphine (0.1 mg/kg) and meloxicam (5 mg/kg), and placed in a stereotactic frame. The skull was exposed and holes drilled to allow virus injection and implantation of fiber optic cannula. Mice were given additional doses of meloxicam each day for 3 days after surgery, and were monitored carefully for 7 days post-surgery.
For VTA cell body recordings (Fig.5a,b ), GCaMP and tdTomato were expressed in VTA dopamine neurons using AAV1-Syn-Flex-GCaMP6f-WPRE-SV40 (titer 6.2 × 1013) and AAV1-CAG-Flex-tdTomato-WPRE-bGH (titer 3.1 × 1013) viruses (Penn Vector Core) in male B6.SJL-Slc6a3tm1.1(cre)Bkmn/J mice. The viruses were mixed and diluted in a ratio of 20% GCaMP6f, 10% TdTomato, 70% saline. 500 nL per hemisphere of the diluted virus was injected at 1 nL/second at AP: −3.3, ML: ±0.4, DV: −4.5 mm relative to bregma. Recordings were made through a 200 um 0.53 NA fiber optic cannula implanted at AP: −3.3, ML: +0.4, DV: −4.3 mm relative to bregma.
For the NAc terminal recordings (Fig.5c,d ) GCaMP was expressed in VTA dopamine neurons using AAV1-Syn-Flex-GCaMP6f-WPRE-SV40 (titer 6.2 × 1013). The virus was diluted 1:10 with saline and 1 μL was injected per hemisphere at AP: −3.3, ML: ±0.4, DV: −4.2 mm relative to bregma. Optic fiber cannula were implanted at AP: 1.4, ML 0.8, DV: 4.1 relative to bregma.
Prior to recording, mice were put on a water restriction schedule where on training days they received 0.5–1.5 mL water from rewards received in the task and on non-training days 1 hour of unrestricted access in their home cage. Mice maintained a typical body weight of >90% pre-restriction levels. Experiments were carried out in accordance with the Oxford University animal use guidelines and performed under UK Home Office Project Licence P6F11BC25.
VTA cell body recordings were acquired using the ‘2 colour time division’ acquisition mode using 470 and 560 nm wavelength LEDs respectively for the GCaMP and tdTomato excitation light and 500–540 and 600–680 nm emission filters for the GCaMP and tdTomato signals. NAc terminal recordings were acquired using the ‘1 colour time division’ acquisition mode using 470 and 405 nm wavelength LEDs respectively for the GCaMP and isosbestic signals.
Acquired signals were bandpass filtered between 0.01 and 20 Hz using a fourth order zero phase filter. The full set of optical components used is listed Table1 as well as in the hardware repository. The Newport photoreceivers were used in DC coupled mode for all recordings.
For VTA cell body recordings (Fig.
For the NAc terminal recordings (Fig.
Prior to recording, mice were put on a water restriction schedule where on training days they received 0.5–1.5 mL water from rewards received in the task and on non-training days 1 hour of unrestricted access in their home cage. Mice maintained a typical body weight of >90% pre-restriction levels. Experiments were carried out in accordance with the Oxford University animal use guidelines and performed under UK Home Office Project Licence P6F11BC25.
VTA cell body recordings were acquired using the ‘2 colour time division’ acquisition mode using 470 and 560 nm wavelength LEDs respectively for the GCaMP and tdTomato excitation light and 500–540 and 600–680 nm emission filters for the GCaMP and tdTomato signals. NAc terminal recordings were acquired using the ‘1 colour time division’ acquisition mode using 470 and 405 nm wavelength LEDs respectively for the GCaMP and isosbestic signals.
Acquired signals were bandpass filtered between 0.01 and 20 Hz using a fourth order zero phase filter. The full set of optical components used is listed Table
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