The Collaborative International Dictionary of English v.0.48:

Vasohypotonic \Vas`o*hy`po*ton"ic\, a. [See Hypo-, and
   Tonic.]
   See Vasodilator.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vasodilator \Vas`o*di*lat"or\, a. [L. vas a vessel + dilator.]
   (Physiol.)
   Causing dilation or relaxation of the blood vessels; as, the
   vasodilator nerves, stimulation of which causes dilation of
   the blood vessels to which they go. These nerves are also
   called vaso-inhibitory, and vasohypotonic nerves, since
   their stimulation causes relaxation and rest.
   [1913 Webster]