Pharmacological manipulation of brain galaninergic system and sexual behavior in male mice.
BACKGROUND
Available data suggest a complex role for the brain galaninergic system in male sexual behavior; however, the results so far obtained in animals with either galanin or galanin antagonists are conflicting.


OBJECTIVE
To define the better influence of galanin on male sexual behavior by studying, in mice, (i) the effect of galanin and of the chimeric galanin peptide M40 on the copulatory performance, and (ii) galanin mRNA levels in hypothalamic arcuate and dorso-medial nuclei.


METHODS
For the behavioral testing, only sexually sluggish male mice were used. Galanin mRNA levels were studied in both sexually potent and impotent mice by means of in situ hybridization. Standard behavioral parameters for sexual behavior were recorded or calculated. Synthetic galanin (0.05, 0.1 or 1 microg/mouse) and M40 (5 or 20 microg/mouse) were intracerebroventricularly (ICV) injected, 15 min before the copulatory test. Galanin mRNA levels were evaluated.


RESULTS
In sexually sluggish male mice, both galanin (0.1 and 1 microg/mouse ICV) and M40 (20 microg/mouse ICV), significantly increased intromission frequency and ejaculation latency; M40 also improved copulatory efficacy. On the other hand, in the hypothalamic arcuate and dorso-medial nuclei, the levels of galanin mRNA were not significantly different in sexually potent and impotent male mice.


CONCLUSIONS
These results show that in sexually sluggish male mice the ICV injection of either galanin or the chimeric analogue M40 greatly prolongs the duration of the copulation; without a reduction of the sexual drive or of the copulatory performance. On the other hand, the hybridization experiments seem to rule out an important physiological role of the brain galaninergic system in the regulation of male sexual behavior, at least in mice.
Benelli
A
A
Department of Biomedical Sciences, Section of Pharmacology, University of Modena and Reggio Emilia,Via Campi 287, 41100 Modena, Italy. benelli.augusta@unimo.it
Bertolini
A
A
Zoli
M
M
Leo
G
G
Filaferro
M
M
Saltini
S
S
Genedani
S
S
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005260:Female; D019004:Galanin / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology*; D017403:In Situ Hybridization; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010446:Peptide Fragments / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology
D004338:Drug Combinations; C079517:M40; D010446:Peptide Fragments; D012333:RNA, Messenger; D019004:Galanin