Article

Plasma prolactin concentrations and copulatory behavior after salsolinol injection in male rats

Division of Laboratory Animal Science, Nippon Medical School, Bunkyo, Tokyo, Japan; Department of Physiology, Kasetsart University, Bangkok, Thailand
Reproductive Medicine and Biology 9(4):205-209. DOI: 10.1007/s12522-010-0060-7

ABSTRACT PurposeThe dopamine-derived endogenous compound, R-salsolinol (SAL), was recently identified as a putative endogenous prolactin (PRL)-releasing
factor. However, how SAL influences copulatory behavior is unknown. In this study, we examined the relationship between SAL
and copulatory behavior in male rats.

MethodsMale Sprague-Dawley rats administered SAL were exposed to female rats in estrus, the plasma PRL concentration was measured,
and the behavioral frequency and time during copulatory behavior were noted.

ResultsIn the control and SAL groups, plasma PRL concentrations at 15min before exposure to the female were 7.3±2.0 and 8.0±1.5ng/ml,
respectively. Moreover, plasma PRL concentrations in males immediately after exposure to the female were 7.4±1.2 and 68.0±5.9ng/ml,
respectively (P<0.05). All (8/8) of the control animals ejaculated in the presence of the female, whereas only 33% (2/6) of the SAL group
ejaculated. An increasing tendency for mount latency and intromission latency and a decreasing tendency for intromission frequency
were observed in the SAL group.

ConclusionsCopulatory behavior was inhibited in male rats after SAL injection, suggesting that SAL is a copulatory behavior inhibiting
factor.

KeywordsCopulatory behavior-Hyperprolactinemia-Male rat-Prolactin-releasing factor-Salsolinol

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