<prompt> Which hormones antagonize the effect of NO and cause the penis to become flaccid after orgasm?Endothelin and norepinephrineEstrogen and progesteroneLuteinizing hormone LH and follicle-stimulating hormone FSHProgesterone and LH  <response>: Norepinephrine is released from the nerve terminals and endothelin is released from endothelial cells in the vasculature, causing vasoconstriction of the vasculature. 