Fasting reduces the responses of the rat vas deferens to sympathomimetics.

The effect of fasting, L-DOPA pretreatment and high glucose medium on the response of the rat vas deferens to sympathomimetics was studied in vitro. The contractile responses of the rat isolated vas deferens were reduced by fasting, the effect being significant after 24-hr fast with noradrenaline and tyramine, after a 48-hr fast with dopamine, and after a 72-hr fast with methoxamine. Treatment with L-DOPA for 7 days before sacrifice abolished the effect of a 24-hr fast in reducing responses to noradrenaline and tyramine, and the response to methoxamine after a 72-hr fast was enhanced. Doubling the concentration of glucose in the solution bathing the isolated vas deferens from rats fasted for 24 hr increased the responses to noradrenaline and tyramine. It is concluded that fasting reduces the responses of the rat vas deferens to sympathomimetics whilst L-DOPA pretreatment and high glucose restore and/or enhance the responses.