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Testosterone or Oestradiol Implants in the Medial Preoptic Area Induce Mating in Noncopulating Male Rats
Author(s) -
AntonioCabrera E.,
Paredes R. G.
Publication year - 2014
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12164
Subject(s) - medicine , endocrinology , testosterone (patch) , hypothalamus , amygdala , castration , androgen , ejaculation , adult male , hormone
Noncopulating ( NC ) male rats are those males that do not mount, intromit or ejaculate when repeatedly tested with receptive females. The lack of sexual behaviour in these males is not associated with alterations in testosterone or oestradiol (E 2 ) plasma concentrations. Instead, it has been shown that androgen receptors are higher and oestrogen receptors are lower in the medial preoptic area ( MPOA ) of NC male rats than those observed in copulating (C) male rats. We have also observed reduced aromatase activity in the MPOA (but not in other brain regions) of NC male rats. The aim of the present study was to determine whether testosterone or E 2 implants in the MPOA of NC male rats could induce sexual behaviour. Accordingly, in Experiment 1, we evaluated the long‐term effects of testosterone or E 2 implants in the MPOA , the ventromedial nucleus of the hypothalamus or the medial amygdala with respect to inducing sexual behaviour in castrated C male rats. Male rats were bilaterally implanted with a guide cannula, either empty or containing testosterone or E 2 . Starting 1 week later, all male rats were mated once weekly for 5 months. As described previously, the site where hormone implants most consistently induced sexual behaviour in castrated C male rats was the MPOA . Experiment 1 extended these findings showing that the males continued mating even 5 months after the implant. In the second experiment, NC males were implanted in the MPOA with a guide cannula empty or filled with testosterone or E 2. One week after the testosterone or E 2 implant, the percentage of males that mounted and intromitted started to increase and, 5 weeks after the implant, 50% of the subjects displayed mounts and intromissions. All NC males implanted with testosterone ejaculated consistently from week 11 after the implant until the end of testing (5 months), whereas all subjects implanted with E 2 ejaculated from week 16 after the implant until the end of testing. These results support the hypothesis that, in the MPOA of NC male rats, there is a hormonal alteration associated with the lack of sexual behaviour.