SEROTONERGIC CONTROL OF ELECTRIC ORGAN DISCHARGE IN GYMNOTUS-CARAPO -ROLE OF 5-HT2A 2C RECEPTOR SUBTYPES/

Resting frequency of the EOD and amplitude of the frequency changes in duced by different stimulus modalities (novelty responses) were measur ed in Gymnotus carapo before and after pharmacological modulation of s erotonergic transmission and in control groups. Stimulation of seroton ergic transmission induced a decrease of resting frequency and the app earance of spontaneous frequency bursts. The amplitude of the transien t change in discharge frequency induced by photic, acoustic, mechanica l and electric stimuli was significantly enhanced after serotonergic s timulation. These effects were also produced by a selective ligand of 5-HT2A/2c receptor subtypes. Selective blockade of the same receptors prevented the agonist effect and induced opposite changes, thus sugges ting the existence of a tonic serotonergic control.