Electroencephalographic coupling in the amygdala and prefrontal cortex in relation to the estrous cycle and duration of vaginocervical stimulation in the rat

• Vaginocervical stimulation induces different cortical and amygdaline functionality.
• The amygdaline synchronization depend of the duration of vaginocervical stimulation.
• High amygdaline synchronization occur in relation to brief periods of VCS in rats.
• The interamygdaline correlation is sensitive to the timing of VCS in proestrus rats.

The influence of the duration of vaginocervical stimulation (VCS) on the electroencephalographic activity (EEG) of medial amygdala (MeA) and prefrontal cortex (PFC) in rats during proestrus-estrus (P-E) and diestrus (D) was examined. Using a glass syringe plunger, a constant force of 300 g was exerted against the cervix during 60 s. Relative power (RP) and correlation of three EEG band frequencies were compared between the first and last 30 s intervals of VCS. A higher RP of the 4–7 Hz band and a lower RP of the fast frequencies were observed in the MeA and PFC in P-E females during the first 30 s of VCS as compared to the last 30 s. Only during P-E, a higher interamygdaline correlation in the 8–12 Hz band and a lower correlation in the 13–21 Hz band during the first 30 s were observed. Similarly, a higher interamygdaline correlation in the 8–12 Hz band was observed during the first 30 s of VCS during P-E as compared to D. During the last 30 s of VCS there was no difference between phases. The VCS evoked EEG changes in the MeA that varied between phases of the estrous cycle and depended on the duration of the stimulation. These effects could be associated with the quantification processes of VCS that has been proposed to occur in the amygdala. These findings show differential responsiveness of the MeA and PFC according to the amount of VCS received, and that the response varies according to the estrous cycle.