Cannabinoid system regulates synaptic transmission in different brain regions. In this work, we study by electrophysiological techniques the effect of cannabinoids on the locus coeruleus (LC) and the dorsal raphe nucleus (DRN), the main noradrenergic and serotonergic nuclei in the central nervous system, respectively. These nuclei play a crucial role in the control of pain, mood,learning/memory, sleep-wake cycle, arousal and rewarding behavior. We demonstrate that cannabinoids alter the firing activity of LC cells and regulate glutamatergic system in this nucleus. We also describe how cannabinoids modulate GABAergic system in the DRN. In summary, our work shows that cannabinoids affect the neurons of the LC and DRN by a complex mechanism. The data of this study could explain why cannabis consumption results in a disruption of attention.