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Abstract

Serotonin is one of the major neuromodulators with a broad range of pharmacological actions and has been implicated in several neurological disorders including schizophrenia. Here we investigate neuronal and metabolic effects induced by the local application of serotonin receptor 1A agonist BP554 in cortex of the non-human primate. We focused on the primary visual cortex, allowing us to robustly induce activation using the presentation of a visual stimulus. We performed electrical recordings of neural activity in conjunction with simultaneous monitoring of the blood oxygenation level dependent (BOLD) signal before, during and after the local application of BP554. Neural activity was analyzed both at the level of the local field potential (LFP) and multi unit activity (MUA). We performed a total of 17 experiments in three subjects. Our main finding was that BOLD activity was largely unaffected by the injection of BP554 (no significant changes in activity, t-test, P = 0.64). Similarly, the application had little effect on LFP activity (no significant changes in activity, t-test, P = 0.56). By contrast, MUA was robustly reduced following the injection of BP554. (Reduction of activity by 34, t-test, P < 0.05). Because LFP as well as BOLD activity are largely related to synaptic activity, our findings suggest that BP554 had little effect on the average level of local processing. The output of the local network, as estimated by MUA activity, is by contrast strongly affected by BP554. This suggests that serotonin may leave local information processing intact, but block the results of the local computations from being transmitted to other brain regions. This network behaviour may contribute to disorders associated with serotonin dysfunction.