Is it purely the nervous system causing vaginal lubrication (arousal)?
There is a good open access review about the effects of different hormones on sexual arousal. In most instances, the hormone is acting on the brain, which signals the information to gonads and genitals via nerves (i.e., the hypothalamic-pituitary-gonadal axis). However, in a study in which I have participated, we found a more direct and probably ancient signaling pathway where the mouse liver, in response to protein intake, was sending a permissive signal to the uterus for reproduction. Whether this holds true for vagina lubrication was not investigated, but I would be optimistic that mechanisms other than nerve communication could play some roles.