Strategies implemented for smoking cessation have shown few successes due, in part, to neuroadaptations following exposure to nicotine¹. To best develop effective strategies uncovering of neuronal mechanism that underpin nicotine dependence is essential. If noninvasive assessment of the neural effects of nicotine exposure were possible such measuring tools could accelerate successful cessation strategies. To this end we employed MEMRI approaches to assess the neuronal responses in rats after acute and chronic nicotine exposures.Brains of live male Wistar rats (300–350 g) were evaluated by a 7T/21 cm MRI scanner (Bruker, Billerica, MA). For acute nicotine exposure, baseline T₁-wt MRI (multi-slice FLASH, TR = 20 ms, α = 20^o) were recorded. Continuous intravenous injection of 50 mM MnCl₂ solution was given by infusion. After administering 30 mg/kg Mn²⁺ in 35 minutes, a bolus of 25% mannitol (5-7 ml/kg; Sigma) was injected to disrupt the brain-blood barrier (BBB). Mn²⁺ was continued for 25 minutes and after ten minutes, either nicotine bitartrate (0.18 mg/kg, n = 6) or PBS (n = 6) was injected. T₁-wt MRI was continuously performed for 45 minutes. In the chronic nicotine exposure study, six rats received a nicotine infusion (3.0 mg/kg/day) for 7 days using mini-pumps implanted subcutaneously. A control group of rats (n = 6) received PBS. MEMRI was performed at 22 hours after the termination of nicotine/PBS infusion. MnCl₂ solution (50 mM) was injected daily for 4 days before MRI with a daily dose of 60 mg/kg. Rats were scanned using T₁-wt MRI (3D FLASH, TR = 20 ms, flip angle = 20^o). The T1-wt images were then registered to a MEMRI-based rat brain atlas² for t-tests to compare regional MRI signal enhancement. The scans were normalized to an external phantom between PBS controls and nicotine infused rats. After MRI, animals were euthanized and brains recovered for immunohistological tests following formalin fixation and paraffin embedding. Five μm thick sections were cut and labeled with mouse monoclonal antibody for c-Fos. Images were captured with 4× objective with a Nuance EX multispectral imaging system fixed to a Nikon Eclipse E800.Acute nicotine exposure: Fig. 1 shows the percentage signal intensity change to the baseline on nucleus accumbens (ACB, Fig. 1A) and hippocampus (HIP, Fig. 1B), respectively. Signal intensity started to increase when MnCl₂ infusion started. The increase became even faster after mannitol injection. After MnCl₂ infusion completed, the intensity became stable. No apparent signal change was observed after PBS injections, while significant increase was found after nicotine injections on both ACB (~2%) and HIP (~4%). C-Fos staining showed higher neuronal activity in nicotine injected rats compared to controls. Representative image of c-Fos expression on HIP is shown (Fig. 3A). Chronic nicotine exposure: a t-test showed significant MRI signal increase on ACB, HIP, prefrontal and insular cortex as demonstrated on Fig 2. Higher c-Fos staining was also observed in rats with chronic nicotine exposure. Representative image of c-Fos expression on HIP of these rats is shown in Fig. 3B.MEMRI is able to detect neuronal activity induced by nicotine exposure as proven by immunohistology using c-Fos staining. The brain regions stimulated by acute nicotine exposure includes ACB and HIP that are involved in drug addiction. The same regions were activated after chronic nicotine exposure. Insular and prefrontal cortices also show activation after chronic nicotine exposure, and are believed to play roles in drug addiction. We demonstrate that MEMRI can be used to assess neuroadaptations from nicotine addiction.