Figure 1.
Location of microinfusion injector tips.
The majority of injections were made directly into the PVT region. Four TTX-treated animals and two CART-treated animals had injections that fell beyond the PVT boundary, and the responding of these animals was assessed to determine the specificity of the observed effects to the PVT. Numbers represent the approximate rostrocaudal distance from bregma. Figures adapted from Paxinos and Watson [44]. Symbols represent different groups; •: saline; ○: TTX; ◊: 0.625 µg CART; □: 2.5 µg CART; X: misplaced TTX; *: misplaced 0.625 µg CART injections; #: misplaced 2.5 µg CART injections. CM: central medial thalamic nucleus; D3V: dorsal third ventricle; IMD: intermediodorsal thalamic nucleus; MDC: mediodorsal thalamic nucleus, central part; MDM: mediodorsal thalamic nucleus, medial part; PVA: Paraventricular thalamic nucleus, anterior part; PVT: Paraventricular thalamic nucleus; PVP: Paraventricular thalamic nucleus, posterior part.
Figure 2.
Microinfusion of TTX or CART into the PVT attenuates cocaine-primed reinstatement.
All animals were tested following a cocaine prime (10 mg/kg, i.p.) preceded by a PVT-directed microinfusion of either saline, 2.5 ng TTX, 0.625 µg CART55-102 or 2.5 µg CART55-102 (n = 6–7). A group of animals served as no-injection controls, and were grouped with saline-treated animals to form a ‘control’ group (CONT). Treatment with TTX or CART produced a significant attenuation of active lever responding following cocaine prime, as compared to controls †: p = .05, ††: p<.01, significantly different to controls (A). Control animals exhibited a significantly higher level of active lever responding than 2.5 µg CART-treated animals in the first ten minutes of reinstatement testing. At all other time points, control animals exhibited significantly higher levels of responding than TTX- and both CART-treatment groups. †: Control group significantly different to TTX-treatment group; #: Control group significantly different to 0.625 µg CART-treatment group; * : Control group significantly different to 2.5 µg CART-treatment group, all ps<.05 (B). Importantly, TTX and CART treatment did not affect responding on the inactive lever, indicating that the observed effects were specific to drug-seeking behaviour rather than an overall reduction in arousal and/or locomotion (C). SA: Average number of active lever presses over last three days of self-administration training period. EXT: Average number of active lever presses over last three days of extinction training. Error bars represent (+ S.E.M.).