The effects of lysergic acid diethylamide on copulatory behaviour in the female rat.

The actions of lysergic acid diethylamide (LSD) on a serotonin- and dopamine-dependent functional test, lordotic behaviour in female rats, and other behaviours were investigated. Increasing doses of LSD inhibited the display of lordosis in increasing numbers of females. Also locomotor activity and habituation of a startle reaction were impaired. Pretreatment with a large single dose of p-chlorophenylalanine, which by itself induced lordosis in all subjects tested, caused an enhancement of the LSD effect, prolonging its duration. When p-chlorophenylalanine was replaced by α-methyl-p-tyrosine, all females showed lordosis by this treatment alone, while a combination with LSD had a significantly briefer effect than this dose of LSD alone. Repeated administration of smaller doses of p-chlorophenylalanine did not by itself alter the response level in a group of females, and together with LSD the effect was of a shorter duration than after the single dose of p-chlorophenylalanine. Inhibition of lordosis was not related to impairment of locomotor capacity. These differential effects after pretreatment with the synthesis inhibitors in addition to other data discussed indicate that certain functional effects of LSD could be related to increased serotonin activity.