Region-selective inhibition of male rat sexual behavior and motor performance by localized forebrain 5-HT injections: a comparison with effects produced by 8-OH-DPAT.
The local application of 5-HT (0-40 micrograms side-1) into the nucleus accumbens was found to inhibit male rat sexual behavior, as evidenced by an increase in number of mounts and intromissions preceding ejaculation and in time to ejaculation. There were no effects on male rat sexual behavior after similar 5-HT injections into other striatal areas, including the dorsolateral, the ventromedial and the posterior neostriatum, as well as the olfactory tubercle. The same groups of animals were also scored for motor activity and body posture after the injection of 5-HT, and only animals injected into the nucleus accumbens showed a statistically significant decrease in motor activity and an increase in the display of a flat body posture. 8-OH-DPAT (0-5 micrograms side-1), injected into the nucleus accumbens, produced a facilitation of the male rat sexual behavior, as evidenced by a decrease in number of mounts and intromissions to ejaculation, as well as in the postejaculatory interval. 8-OH-DPAT injections into the nucleus accumbens produced a decrease in motor activity and an increase in the per cent animals with a flat body posture. Injections into the olfactory tubercle had no effects on the sexual behavior or on the motor activity, whereas the per cent flat body posture was increased. Local application of 8-OH-DPAT (0-5 micrograms) into the median raphe nucleus, facilitated male rat sexual behavior, as evidenced by a decrease in number of intromissions preceding ejaculation and in time to ejaculation. The same doses of 8-OH-DPAT injected into the dorsal raphe had no effects on the sexual behavior. In an additional experiment, 3 groups of animals were injected with 5-HT (40 micrograms) or 8-OH-DPAT (5 micrograms) into the nucleus accumbens, the dorsal and the median raphe nuclei and thereafter observed for treadmill performance. No statistically significant effects were found after injections in any of these brain areas. The present results strongly suggest an inhibitory role of ventral forebrain 5-HT in the mediation of male rat sexual behavior. The facilitation produced by 8-OH-DPAT is possibly due to a blockade of 5-HT2 receptors. Facilitation by 8-OH-DPAT of the male rat copulatory performance after median raphe injections is probably due to stimulation of 5-HT1A autoreceptors in this brainstem region. In contrast to their opposite effects on sexual behavior, both compounds produced a decrease in motor activity and an increased display of flat body posture after accumbens injections.(ABSTRACT TRUNCATED AT 250 WORDS)
Hillegaart
V
V
Department of Psychology, University of Göteborg, Sweden.
Ahlenius
S
S
Larsson
K
K
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D003342:Corpus Striatum; D004542:Ejaculation / Q000187:drug effects; D005260:Female; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens; D009830:Olfactory Bulb; D011597:Psychomotor Performance / Q000502:physiology*; D011903:Raphe Nuclei; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013764:Tetrahydronaphthalenes / Q000008:administration & dosage / Q000494:pharmacology*
D013764:Tetrahydronaphthalenes; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin