Individual differences in male rat ejaculatory behaviour: searching for models to study ejaculation disorders.
In addition to investigating sexual function in rats that display normal ejaculatory behaviour, studying rats that are either 'hyposexual' or 'hypersexual' may provide important insights into the aetiology of ejaculatory dysfunctions in men, such as premature and retarded ejaculation. To this end, rats were matched into groups of 'sluggish', 'normal' and 'rapid' ejaculators based on their ejaculation frequencies displayed in a series of weekly sexual behaviour tests. Selecting rats on this parameter revealed large and stable differences in other parameters of sexual behaviour as well, including ejaculation latency and mount frequency but not intromission frequency and mount latency, putative indices of sexual motivation. Neuroanatomically, Fos immunoreactivity as a measure of neuronal activation was increased in rapid ejaculators compared with sluggish ejaculators in ejaculation-related brain areas, presumably associated with the differences in ejaculatory behaviour. Although the total number of oxytocin neurones within subregions of the hypothalamus did not differ between groups, in the supraoptic nucleus of the hypothalamus more oxytocin neurones were activated in rapid ejaculators compared with the other groups. Apart from the differences observed in ejaculatory behaviour, groups did not differ with respect to their locomotor activity and approach-avoidance behaviour as measured in the elevated plus-maze. Finally, apomorphine-induced stereotypy was similar in sluggish and rapid ejaculators, suggesting no large differences in dopamine susceptibility. Altogether, the present results suggest stable differences in male rat ejaculatory behaviour. Further exploring the neurobiological mechanisms underlying these differences may be a promising approach to gain insights into the aetiology of sexual dysfunctions such as premature, retarded or an-ejaculation.
Pattij
Tommy
T
Department of Anatomy, University Medical Center St Radboud, Nijmegen, The Netherlands. t.pattij@vumc.nl
de Jong
Trynke R
TR
Uitterdijk
Andre
A
Waldinger
Marcel D
MD
Veening
Jan G
JG
Cools
Alexander R
AR
van der Graaf
Piet Hein
PH
Olivier
Berend
B
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001522:Behavior, Animal; D001921:Brain / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D004195:Disease Models, Animal; D018491:Dopamine Agonists / Q000494:pharmacology; D004347:Drug Interactions; D004542:Ejaculation / Q000187:drug effects / Q000502:physiology*; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005260:Female; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010121:Oxytocin / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D012726:Sexual Behavior, Animal / Q000187:drug effects; D012735:Sexual Dysfunction, Physiological / Q000503:physiopathology*; D013239:Stereotyped Behavior / Q000187:drug effects / Q000502:physiology
D018491:Dopamine Agonists; D016761:Oncogene Proteins v-fos; D017366:Serotonin Receptor Agonists; D010121:Oxytocin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D001058:Apomorphine