The sense of smell is important for survival of many species with respect to finding food and shelter, avoiding danger and interacting with conspecifics. Neuromodulators such as acetylcholine, dopamine, noradrenaline and serotonin can act broadly on brain networks to adjust processing to diverse situations and behavioral needs. In this respect, the present study investigates the impact of serotonin (5HT) manipulation within the olfactory bulb (OB) on neural activity in response to odor stimuli in adult Long Evans Hooded rats. 5HT modulation of olfactory processing has not been studied extensively. We ask to what extend 5HT modulation of early olfactory processing in the olfactory bulb affects cortical responses to odorants. Towards this goal, we manipulated 5HT action in the olfactory bulb via intracerebral infusions of 5HT in rats Our results demonstrate that 5HT significantly increased spontaneous firing rates in both the OB and PC as well as enhanced odor sensitivity of cortical neurons. These findings underscore the importance of 5HT in modulating neural activity within the olfactory pathway, shedding light on the mechanisms underlying odor processing and sensitivity.