Different doses of estradiol benzoate induce conditioned place preference after paced mating.
ABSTRACT The ovarian hormones estrogen and progesterone are required for the complete display of sexual behavior in female rats. Paced mating produces a reward state in intact cycling and ovariectomized (OVX), hormonally primed females as evaluated by the conditioned place preference (CPP) paradigm. Most of the studies that have evaluated CPP induced by paced mating in OVX females have used relatively high doses of estradiol benzoate (EB). In the present study we determined if different doses of EB, combined with progesterone (P), could induce CPP after paced mating. For this purpose OVX female rats were divided in five groups that received one of different doses of estradiol benzoate (5, 2.5, 1.25 or 0.625 μg estradiol+0.5mg of progesterone) before being allowed to pace the sexual interaction and conditioned in a CPP paradigm. We found that the lowest dose of EB used (0.625 μg) significantly reduced the lordosis quotient and the lordosis coefficient. Even though these females paced the sexual interaction, they didn't change its original preference, suggesting that sexual interaction did not induce a positive affective, reward state. Females allowed to pace the sexual interaction with higher doses of EB developed CPP after paced mating. These results indicate that a threshold of estradiol is required for paced mating to induce CPP.
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ABSTRACT: The sequential organization of sexual behavior of the female rat is described, eventually leading to the lordotic posture, shown during mating. A complex set of signals: olfactory, cutaneous sensory as well as genitosensory, are guiding the female to this specific posture, eventually. Genitosensory signals converge in the lumbosacral levels of the spinal cord, from where they are dispersed to a series of supraspinal brain areas, in the brainstem, thalamus, hypothalamus and limbic system. The similarity with the neural activation patterns observed in the male rat is remarkable. In a number of brain areas, however: the midbrain periaqueductal gray, the ventrolateral part of the ventromedial hypothalamic nucleus (VMHvl) and the medial preoptic -lateral septum regions, specific male-female differences have been observed. Especially the VMHvl is an intriguing area, as it has been shown that the same neurons may be involved in 'opposite behaviors' like aggression and the induction of lordosis! The motor mechanisms controlling the lordosis posture in the rat as well as in some other mammals are discussed, as well as some aspects of the reward mechanisms contributing to female sex. We conclude that we have collected a great amount of neurophysiological knowledge over the last 20 years, but that the unresolved questions are still numerous. In this field, there is still much to explore.Pharmacology Biochemistry and Behavior 01/2013; · 2.61 Impact Factor
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ABSTRACT: We have previously established the rewarding value of clitoral stimulation (CLS) through the demonstration that manual, distributed, CLS induces a significant conditioned place preference (CPP) and conditioned partner preference in naïve, hormonally primed and non-hormonally primed rats. The present experiment asks whether previous sexual experience might inhibit the ability of clitoral stimulation to induce a conditioned place preference. Female Long-Evans rats were ovariectomized and treated with 10μg of estradiol benzoate (EB) 48h and 500μg of progesterone (P) 4h prior to receiving either 0, 1, or 5 consecutive copulatory sessions with a sexually vigorous male. Each copulatory session ended when females received at least 1 ejaculation. Females then experienced 10 alternating trials of distributed CLS or no CLS paired with one side of a non-biased CPP box under the same hormone-priming regimen. Females that experienced 5 consecutive copulatory sessions did not develop a significant place preference indicated by both a preference score (the proportion of time spent in the reinforced chamber) and a difference score (time in the non-reinforced chamber minus the time in the reinforced chamber) compared prior to and following the 10 conditioning trials. This suggests that repeated copulatory experience might induce a desensitization of the genitosensory circuit since copulation includes both clitoral, and vaginocervical stimulation from mounts plus intromissions. Alternatively, repeated sexual experience prior to conditioning may generate a UCS pre-exposure effect that cannot be altered when manual clitoral stimulation is paired with a new environment.Physiology & Behavior 06/2013; · 3.16 Impact Factor
Article: Neurobiology of social attachments[Show abstract] [Hide abstract]
ABSTRACT: Many types of social attachments can be observed in nature. We discuss the neurobiology of two types 1) intraspecific (with a partner) and 2) parental (with the offspring). Stimuli related to copulation facilitate the first, whereas pregnancy, parturition and lactation facilitate the second. Both types develop as consequence of cohabitation. These events seem to stimulate similar neural pathways that increase 1) social recognition, 2) motivation, reward; and 3) decrease fear/anxiety. Subregions of the amygdala and cortex facilitate social recognition and also disinhibition to decrease rejection responses. The interrelationship between MeA, BNST, LS may mediate the activation of NAcc via the mPOA to increase motivation and reward. Cortical areas such as the ACC discriminate between stimuli. The interaction between OT and D2-type receptors in NAcc shell facilitates intraspecific attachment, but D1-type appears to facilitate parental attachment. This difference may be important for maternal females to direct their attention, motivation and expression of attachment towards the appropriate target.Neuroscience & Biobehavioral Reviews 01/2014; · 10.28 Impact Factor