Biology subjects

Huijgens, P. T.

Publications and source records attributed to Huijgens, P. T..

4 recordsLinked to original sources

bioRxiv2021

Male rat sexual behavior: insights from inter-copulatory intervals

The assessment of sexual behavior in male rats with the aim of unraveling underlying neurobiological mechanisms has in the recent decades been reduced to the annotation of mounts, intromissions and ejaculations. To provide a better understanding of the structure and patterns of copulation, it is necessary to extend and tailor the analysis to the natural organization of male rat copulation. This will lead to better formulation of hypotheses about neurobiological underpinnings of behavior. Mounts and intromissions are naturally organized in mount bouts consisting of one or more copulatory behaviors and are interspersed with time outs. We hypothesized that time outs and the post-ejaculatory interval (inter-copulatory intervals) are related and possibly under the control of a common copulatory inhibition mechanism that is the result of penile sensory stimulation. To test this hypothesis, we analyzed sexual behavior in male rats of three different cohorts from three different laboratories. Results showed that the post-ejaculatory interval and mean time out duration are strongly correlated in all cohorts analyzed. In addition, we showed that individual time out duration is at least partially predicted by the sum of sensory stimulation of copulatory components in the preceding mount bout, with more penile stimulation associated with longer time outs. These findings suggest that both time out and post-ejaculatory interval duration may be determined by the magnitude of sensory stimulation, which inhibits copulation. Whether the same neural pathways are involved in the central orchestration of both time outs and the post-ejaculatory interval should be subject to future studies.

neuroscience↗

bioRxiv2021

Silencing and stimulating the medial amygdala impairs ejaculation but not sexual incentive motivation in male rats

The medial amygdala (MeA) is a sexually dimorphic brain region that integrates sensory information and hormonal signaling, and is involved in the regulation of social behaviors. Lesion studies have shown a role for the MeA in copulation, most prominently in the promotion of ejaculation. The role of the MeA in sexual motivation, but also in temporal patterning of copulation, has not been extensively studied in rats. Here, we investigated the effect of chemogenetic inhibition and stimulation of the MeA on sexual incentive motivation and copulation in sexually experienced male rats. AAV5-CaMKIIa viral vectors coding for Gi, Gq, or no DREADDs (sham) were bilaterally infused into the MeA. Rats were assessed in the sexual incentive motivation test and copulation test upon systemic CNO or vehicle administration. We report that MeA stimulation and inhibition did not affect sexual incentive motivation. Moreover, both stimulation and inhibition of the MeA decreased the number of ejaculations in a 30 minute copulation test and increased ejaculation latency and the number of mounts and intromissions preceding ejaculation, while leaving the temporal pattern of copulation intact. These results indicate that the MeA may be involved in the processing of sensory feedback required to reach ejaculation threshold. The convergence of the behavioral effects of stimulating as well as inhibiting the MeA may reflect opposing behavioral control of specific neuronal populations within the MeA.

neuroscience↗

bioRxiv2020

Effects of gonadectomy and androgen on neuronal plasticity in motivation and reward related brain regions in the male rat

Gonadal hormones affect neuronal morphology to ultimately regulate behavior. Here, we investigated the effect of both castration and androgen replacement on spine plasticity in the nucleus accumbens shell and core (NAcSh and NAcC), caudate putamen (CPu), medial amygdala (MeA), and medial preoptic nucleus (MPN). Intact and castrated (GDX) male rats were treated with dihydrotestosterone (DHT, 1.5mg) or vehicle (oil) in 3 experimental groups: intact-oil, GDX-oil and GDX-DHT. Spine density and morphology, measured 24 hours after injection, were determined through 3D reconstruction of DiI-labeled dendritic segments. GDX decreased spine density in the MPN, which was rescued by DHT treatment. MeA spine density increased in GDX-DHT animals compared to intact-oil animals. In the NAcSh, DHT decreased spine density, and also rapidly increased the number of pCREB+ cell bodies. These findings indicate that androgen signaling plays a role in the regulation of spine plasticity within neurocircuits involved in motivated behaviors.

neuroscience↗

bioRxiv2020

Female rat sexual behavior is unaffected by perinatal fluoxetine exposure

Serotonin plays an important role in adult female sexual behavior, however little is known about the influence of serotonin during early development on sexual functioning in adulthood. During early development, serotonin acts as neurotrophic factor, while it functions as a modulatory neurotransmitter in adulthood. The occurrence of serotonin release, could thus have different effects on behavioral outcomes, depending on the developmental period in which serotonin is released. Because serotonin is involved in the development of the HPG axis which is required for puberty establishment, serotonin could also alter expression patterns of for instance the estrogen receptor (ER). The aim of our study was to investigate the effects of increased serotonin levels during early development on adult female rat sexual behavior during the full behavioral estrus in a seminatural environment. To do so, rats were perinatally exposed with the selective serotonin reuptake inhibitor (SSRI) fluoxetine (10 mg/kg FLX) and sexual performance was tested during adulthood. All facets of female sexual behavior between the first and last lordosis (behavioral estrus), and within each copulation bout of the behavioral estrus were analyzed. Besides the length and onset of the behavioral estrus and the sexual behaviors patterns, other social and conflict behavior were also investigated. In addition, we studied the effects of perinatal FLX exposure on ER expression patterns in the medial preoptic nucleus, ventromedial nucleus of the hypothalamus, medial amygdala, bed nucleus of the stria terminalis, and the dorsal raphe nucleus. The results showed that perinatal fluoxetine exposure has no effect on adult female sexual behavior. The behavioral estrus of FLX-females had the same length and pattern as CTR-females. In addition, FLX- and CTR-females showed the same amount of paracopulatory behavior and lordosis, both during the full behavioral estrus and the "most active bout". Furthermore, no differences were found in the display of social and conflict behaviors, nor in ER expression patterns in the brain. We conclude that increases in serotonin levels during early development do not have long-term consequences for female sexual behavior in adulthood.

animal behavior and cognition↗