The spinal location where microstimulation evokes ejaculation related events corresponds to the LSt neuron area. (a) Strong current injections through the stimulation electrode at the end of the experiment marked the spinal location from which ejaculation and ejaculation related events could be evoked (spinal cord section at L4, cc = central canal). (b) Left: Δp(SV) response (red) in a single rat for various electrode depths, ie vertical distance from the dorsal surface of the spinal cord at L4 level. Green line indicates stimulation period, red numbers stimulation sequence. Middle: corresponding maximal amplitude of Δp(SV) (red dots) vs. electrode depth (vertical axis). The Gaussian function (black) used for data fitting peaks at −1540 μm from the spinal cords’ dorsal surface. Right: summary data for the maximal amplitude of Δp(SV) and electrode depth (n = 9, red) with mean Gaussian fit (black). For each animal, data was normalized by the Δp(SV) maximal amplitude and the peak position of the Gaussian. Microstimulation applied at L2 and L4 evoked the highest maximal amplitude of Δp(SV) (c) and BSM-rEMG (d). Animal numbers indicated for spinal levels. (e) When placing two electrodes spaced 500 μm laterally at L4, significantly larger maximal amplitudes of Δp(SV) (red) and BSM-rEMG (black) were evoked near the spinal cord midline.