Electrophysiological correlates of the mesoaccumbens system during male rat sexual behaviour

It is well known that during the male rat sexual interaction different levels of arousal or sexual motivation are involved and that these motivational changes are associated with variations in the level of dopamine (DA); however, it is not yet known if these changes are associated with a different functionality of the nucleus Accumbens (Acc) and Ventral Tegmental Area (VTA), neural structures that constitute the DA mesoaccumbens system. Thus, in this study was simultaneously recorded the electroencephalogram (EEG) from the VTA and the Acc in order to determine if the EEG correlation (r) between these structures shows characteristic patterns in relation to four different conditions of sexual arousal during the male rat sexual interaction: 1) basal-quiet state (BS); 2) exposure to an inaccessible oestrous female (IF); 3) post-intromission (PI); and, 4) post-ejaculation (PE). Both Acc and VTA showed an increased relative power (RP) in the 8-12 Hz band during the PI condition as compared to the other periods. The correlation patterns between Acc and VTA were sensitive to different arousal levels involved in the male rat sexual interaction: those of the interaccumbens and intertegmental r in the 4-7 and 13-21 Hz bands decreased specifically in the IF condition, when the male rats experienced an aroused state as a result of their exposure to remote stimuli from an inaccessible estrous female; whereas the degree of interaccumbens r in the 8-12 Hz band and those of Acc-VTA in both hemispheres increased specifically in the PI condition, in which the male showed a moderate level of anxiety or alertness provoked by the removal of the female. During the non-sexually aroused states, i.e., basal awake-quiet state and PE condition, no changes were observed. These results suggest the possible participation of the Acc and VTA in both the processing of remote stimuli from an oestrous female and in the aroused state that follows the intromission response, which would indicate that these connections between Acc and VTA are sensitive to the different sexual motivational/arousal states involved in the male rat sexual interaction.