Functional MRI (fMRI) and graph theory offer an objective and analytical approach to address brain network changes associated with psychiatric disorders¹; however its use in animal studies have been limited in psychiatric disorders like drug use disorders. Drug abuse has detrimental effects on the brain function, at short and long time scales, which lead to drug use disorders. In vivo non-invasive biomarkers are needed to determine the neurobiological outcomes of addictive drugs on the brain². In the present study we determined the effects of two addictive psychostimulant drugs, 3,4-methylenedioxypyrovalerone (MDPV) and cocaine, using various graph measures of network connectivity in rodents. MDPV is a designer cathinone drug that is present in formulation of street drugs known as ‘bath salts’³. In this study we investigate the short-term effect of a single dose of the psychostimulant drugs at 1 and 24 hrs.Two resting state fMRI datasets were collected in 4.7T Agilent system at 1 and 24 hrs after i.p. administration of 1.0 mg kg^-1 of MDPV (n_1hour = 8, n_24hour = 8), cocaine of 15 mg kg^-1 (n_1hour = 8, n_24hour = 6), and a control group administered with saline (n_1hour = 7, n_24hour = 6) using a 2-shot spin echo EPI sequence. The acquisition parameters were: TR/TE = 1000/45 ms, and 210 repetitions for a total acquisition time of ~7.5 mins. Imaging was conducted while rats were under 0.5% isofluorane/0.02 mg kg^-1 dexmedetomidine anesthesia (70%N₂/30%O₂ at 0.1L/min). Images were processed for seed-based functional connectivity analysis using a segmented atlas of the rat brain using FSL⁴ and AFNI for 150 anatomical regions. Networks were generated with equal graph densities (15% of all possible connections). To determine the network differences of MDPV and cocaine induced alterations in connectivity we compared network relevant measures (i.e. node strength, path length, and clustering coefficient) to controls. Finally, the brain networks were visualized using BrainNet⁵.Comparison between saline and drug administered shows a reduction in the connectivity at 1 hr however at 24 hrs is no longer observed (Figure 1). The clustering coefficient, an indicator of network integration, was reduced greatly at 1 hr for both drug groups compared to saline, but not at 24 hr. The path length also showed the same reduction at 1 hr and not at 24 hrs. It is interesting to note that saline injections at the 1hr time point was a major driver of heightened connectivity, which waned 24 hrs after saline injection. This experience immediately prior to imaging influence connectivity, like overall strength and small-world topology. Moreover, while drug administered showed a lower connectivity at 1 hr post-treatment, it showed an increased connectivity at 24 hrs (compared to saline groups for their respective time points). We observed that all groups achieved a uniform small-worldness level at 24 hrs. To sum, while saline administration to produce an increase in connectivity, cocaine and MDPV reduce these brain functional connectivity features. These effects are transient and a uniform topology between groups can be observed 24 hrs after initial saline and drug treatments.These results suggest that the brain maintain efficient information transmission through short path lengths, under the effects of drugs, during the first hour after administration; however, their integration is affected by reducing the clustering of local communities. This suggests a mechanism of disruption of local information processing in the brain. However, after 24 hrs after administration brain activity is restored. After the first hr there is a higher level of connectivity in saline compared to 24 hours after saline injection, which seems to imply there is a response during the handling of the rats and administration of the drug that can affect resting state connectivity (even under anesthesia). The latter results suggest a novel experience-associated modulation of resting-state networks that deserves further investigation. It also suggest acclimatization to handling is a confounding variable that needs to be accounted for in future experiments. Finally, under acute treatment conditions, the two psychostimulants studied here produce only transient effects lasting at least 1 hr. It remains to be determined whether longer lasting network changes can be observed following more realistic and chronic drug intake paradigms.