Biomedical subjects
A L Louwerse
Publications and source records attributed to A L Louwerse.
Changes in male copulatory behavior after sexual exciting stimuli: effects of medial amygdala lesions.
A paradigm was developed to investigate how precoital sexual arousal affects parameters of sexual behavior in male rats. Estrous females in a wire mesh cage were used to induce sexual arousal before the sexual interaction test. In control procedures, males were presented in a wire mesh cage or else there was no stimuli at all. The results indicate that ejaculation latency is consistently reduced after preexposure to a female, but not after preexposure to a male, showing that the effect is specific for precoital sexual arousal. Other parameters were affected by precoital sexual arousal in some, but not in all experiments. Reductions in intromission latency moreover, were observed after both preexposure to a male and preexposure to a female, indicating that general social excitement affects this parameter. Preexposure to females for 10 minutes or 3 hours produced similar results. It was subsequently found that medial amygdala-lesioned (AME) animals differed from sham-lesioned (SHAM) controls with respect to their reaction to precoital sexual arousal. The results show that AME-lesioned animals, in contrast to SHAM-animals, do not show reduced ejaculation latencies after preexposure to an estrous female. The results are in line with the idea that AME-lesioned animals are deficient in the assimilation of information on sexual exciting stimuli.
Cerebral glucose utilization during conditioned sexual arousal.
Local cerebral glucose utilization was investigated in male rats during conditioned sexual arousal. Increased glucose utilization was found in three amygdaloid nuclei after exposure to a stimulus associated with exposure to a sexually active female. No changes were observed in areas known to be of crucial importance for the expression of consummatory aspects of sexual behavior. These results corroborate and extend previous results showing a dissociation between the expression of appetitive and consummatory aspects of sexual behavior at a neural level.
Lesions of the SDN-POA inhibit sexual behavior of male Wistar rats.
Discrete bilateral lesions in the SDN-POA of sexually naive adult male rats were found to decrease the number of animals ejaculating and/or to increase latencies to the first mount, intromission and ejaculation. The deleterious effects of the lesions disappeared after 4 tests for sexual behavior but were reinstated when the males were tested under suboptimal conditions, i.e., when they were tested with a marginally receptive female or when they had only limited access to the stimulus female. It was subsequently shown that males with a bilaterally lesioned SDN-POA still showed an increase in plasma testosterone. LH and prolactin levels in response to sexual stimulation. Effects of the lesions on scent marking were not found. Together with previous data indicating that SDN-POA-lesions disrupt masculine sexual behavior in females, these data are taken as evidence that the SDN-POA plays a role in the regulation of masculine sexual behavior. The data further suggest that previously reported negative results of SDN-POA-lesions on masculine sexual behavior in male rats might be attributed to the use of sexually experienced instead of sexually inexperienced animals.
Sexual behavior and sexual orientation of the female rat after hormonal treatment during various stages of development.
The amount of circulating sex steroids during Postnatal Days 30-90 was varied in normally developed and in androgenized female rats. The influence of these manipulations on sexual behavior and sexual orientation was investigated. Normally developed or neonatally androgenized females were ovariectomized and implanted with estradiol through Postnatal Days 30-90 or sham-implanted. The remaining subjects were left intact during that period. The hormonal condition during Postnatal Days 30-90 significantly affected the behavior of normally developed females, but affected the behavior of neonatally androgenized females only to minor extent. Estrogen implants in normally developed females enhanced masculine sexual responses and induced a female-directed sexual orientation. Feminine sexual responses were unaffected by this treatment. Sham-implanted, normally developed females showed a male-directed sexual orientation and fewer masculine sexual responses than subjects which were left intact during Postnatal Days 30-90. Neonatal androgen treatment in general resulted in elevated levels of masculine Neonatal androgen treatment in general resulted in elevated levels of masculine sexual responses, inhibited feminine sexual behavior, and facilitated a female-directed sexual orientation.
Effects of lesions of the sexually dimorphic nucleus on sexual behavior of testosterone-treated female Wistar rats.
Discrete bilateral lesions were placed into the sexually dimorphic nucleus (SDN) of the medial preoptic area (MPOA) of ovariectomized female Wistar rats, chronically treated with testosterone (T). Effects of these lesions upon masculine and feminine sexual behavior were studied by comparing the results of pre- and postoperative tests, using sham-operated and unoperated females as controls. Bilaterally-lesioned and, to a lesser extent, unilaterally-lesioned females, showed a marked and significant reduction of masculine sexual behavior (i.e., mounting), especially in the first postoperative tests. Feminine sexual responses, i.e., receptive and proceptive behavior, although slightly lower in bilaterally-lesioned females, did not change significantly. Sexual partner preference, operationalized as the choice between a receptive female and a sexually active male, remained unaffected by the lesions. Plasma levels of testosterone were similar in the various groups. It is concluded that the SDN may be functionally implicated in the control of masculine sexual behavior in T-treated females.
Gonadal steroid influence upon sexual and aggressive behavior of female rats.
The present experiment investigates the activation of aggressive and sexual behaviors by gonadal hormones in female rats of the S3-strain. In the first experiment three doses of testosterone propionate (TP) were chronically injected. In the second experiment effects of TP were compared to those of estradiol benzoate (EB) and methyltrienelone (R1881), a synthetic, unaromatizable androgen. Females of the S3-strain were tested against TP-treated female Wistar rats as opponents, and masculine and feminine sexual responses were assessed in the test for aggression as well as in separate tests with sexually active stimulus animals. The results of the first experiment indicate that TP in all doses, increased aggressive as well as sexual behavior equally, although plasma testosterone levels differed significantly between the groups. In the second experiment, EB significantly decreased overall aggression as compared to control-treatment. TP- and R1881-stimulated fighting, particularly, as the most offensive parameter of aggression, but did not increase overall levels of aggression. Tests for sexual preference in which the choice between a sexually active male or female was given, indicated that TP-treated females stayed near males with longer durations. Scentmarking frequencies, measured in the semiopenfield test, were effectively activated by TP-treatment. EB- and R1881-treatment resulted in intermediate levels of marking behavior.