The significance of dopamine, versus other catecholamines, for L-dopa induced facilitation of sexual behavior in the castrated male rat.

The effects of a wide dose range of L-DOPA on male rat sexual behavior were investigated. The animals were castrated as adults and supplied with small amounts of testosterone propionate. It was found that doses of L-DOPA up to 2.5 mg/kg facilitated, while higher doses inhibited, sexual behavior in animals pretreated with pargyline, 20 mg/kg, + MK486, 50 mg/kg. The effects of L-DOPA on sexual behavior were not restricted to the copulatory act, but included elements preceding the copulatory act as well. Most of the facilitatory effects of L-DOPA 2.5 mg/kg were prevented by the dopamine receptor blocker pimozide; 0.10 mg/kg. It is concluded that dopamine is the catecholamine of major importance in mediating the L-DOPA induced facilitation of sexual behavior in the castrated male rat. However, some elements of the copulatory act appear to be modified by noradrenaline and/or adrenaline as well.