Behavioral, and neural mechanisms of conditioned partner preference in the female rat

We assessed the development of a conditioned partner preference in female rats towards males associated with paced copulation (PC), relative to nonpaced copulation (NPC). Chapter 1 assessed the behavioral mechanisms. Ovariectomized, hormone-primed females were conditioned to associate an odor or a strain of male with PC. A partner preference test occurred in an open field with two tethered males in opposite corners, one associated with PC and the other with NPC. Paired females (relative to unpaired or random-paired groups) developed a partner preference for PC-related males. They displayed more solicitations and hops and darts, and were more likely to choose the PC-related male for their first ejaculation. Similarly, strain conditioning produced partner preference towards the PC-related male, regardless of the strain; although females were more likely to receive their first ejaculation from the PC-related male only if it was of their own strain. The experiments in Chapter 2 assessed neuroanatomical correlates. The brains of females in both paired and unpaired conditions were processed for Fos-immunoreactivity (Fos-IR) following exposure only to the conditioned stimulus (CS) associated either with PC or with NPC. The CS paired with PC induced more Fos-IR in the piriform cortex, the medial preoptic area, and the ventral tegmental area, compared to the induction by the same CS associated with NPC. The experiments in Chapter 3 assessed neurochemical mechanisms. In Part 1, females were treated with the general opioid antagonist naloxone (4 mg/kg) before every conditioning trial, but were drug-free during the final partner preference test. Naloxone treated females did not develop a conditioned partner preference. In Part 2, females were treated with the dopamine antagonist flupenthixol (.25 mg/kg) before conditioning trials. Only Long-Evans females failed to develop an olfactory conditioned partner preference, just like naloxone-treated females. However, flupenthixol had no effect on conditioned preference for a strain of male in Wistar females. The experiments in Chapter 4 depict preliminary data on the activation of oxytocin, vasopressin and gonadotrophin-releasing hormone (GnRH) neurons following exposure to the CS associated with PC. These data show trends toward a significant activation of Fos within oxytocin neurons in the paraventricular nucleus of the hypothalamus, and GnRH neurons in the anterior hypothalamus, in paired females exposed to the CS. These results demonstrate that the sexual reward induced by PC can be associated with cues on a partner to develop a conditioned preference. When this occurs via olfactory conditioning of a neutral odor, the mechanisms depend on the interaction of opioids and dopamine in mesolimbic areas. However, the conditioning process for a strain of male appears to depend only on opioids

Stress during puberty facilitates precancerous prostate lesions in adult rats

Puberty can be a critical period for the long-term development of diseases, especially for stress-related disorders that depend on neuroendocrine and immune responses. Some organs like the prostate are prone to diseases that result from neuroendocrine or immune challenges, such as cancer. Aim: In the present study, we assessed the long-term effects of an acute pubertal stressor (immune-challenge) on the development of precancerous lesions in adult rats, and compared them with testosterone-induced prostatic lesions. Materials and Methods: Pubertal male rats received a single injection of lipopolysaccharide (LPS) or saline during puberty (5 weeks old). At adulthood (8 weeks old) males were subcutaneously implanted with either an empty capsule or filled with testosterone propionate (100 mg/kg). This resulted in a total of five groups: 1) intact untreated, 2) saline-treated and implanted with a blank capsule, 3) saline-treated and implanted with a testosterone capsule, 4) LPS-treated and implanted with a blank capsule, 5) LPS-treated and implanted with a testosterone capsule. Four weeks later, the rats were sacrified and their prostates processed for histology (hematoxylin and eosin stain) and blood serum processed for hormone analysis (testosterone and corticosterone). Results: Males treated with LPS (stressed during puberty via immune challenge) expressed epithelium dysplasia (specially in the ventral prostate), anisocytosis, presence of mononuclear cells, anisokariosis, non-basal polarity, abnormal nucleus-cytoplasm ratio, proplastic myoepithelium, and granular content in the lumen. These histological alterations were similar, but less severe than those observed in males implanted with testosterone during adulthood. Conclusion: These results indicate that pubertal exposure to an immune challenge (stress) facilitates the long-term development of prostatic lesions in adult male rats

Long-term administration of prolactin or testosterone induced similar precancerous prostate lesions in rats

Evidence indicates that prolactin plays a crucial role in the normal function and development of the prostate, but abnormal high levels of the hormone are associated with hyperplasia and cancer of the gland. Aims: The present study was designed to describe the progressive specific histological abnormalities in the prostate of rats with chronic hyperprolactinemia. Material and Methods: Prolactin was administered during 4; 12 or 24 weeks, and the resulting prostatic alterations were compared with control rats, and also with those treated with testosterone, or the combination of prolactin + testosterone. Results: Rats treated with prolactin, testosterone or prolactin + testosterone expressed precancerous histological abnormalities in the dorsolateral and ventral portions of the prostate as early as in 4 weeks of treatment, but in all cases the malignancy increased after 12 or 24 weeks of treatment. Conclusion: Our study confirms that chronic hyperprolactinemia is a cause of prostate precancerous pathologies. Key Words: prolactin, prostate, cancer, dysplasia, testosterone

Effect of copulation on potentially precancerous prostate lesions, serum testosterone and prolactin levels in rats

The prostate is an exocrine reproductive gland that participates in ejaculation and it is prone to diseases, including cancer. Aim: In the present study, we assessed the long­term effects of copulation on the development of precancerous lesions in rats, and compared them with testosterone­induced prostatic lesions. Materials and Methods: One group of Wistar males was given 10 copulatory sessions to one ejaculation with ovariectomized, hormone­primed females. Sessions occurred twice per week for a total of ten trials. A second group was exposed to females during the same trials, but physical contact was prevented. In addition, each group received a subcutaneous implant in the back either filled with testosterone propionate (T, 100 mg/kg) or empty. This resulted in four subgroups: 1) Control + No sex, 2) Control + Sex, 3) T + No sex and 4) T + Sex. Two days after the 10th trial all the males were sacrificed for prostate histo logy (H&E) and hormone analysis (testosterone and prolactin). Results: Males from the group Control + No sex expressed normal histo logy. However, those in the groups Control + Sex and T + No sex expressed metaplasia and dysplasia in both the dorsolateral and ventral portions of the prostate, respectively. Interestingly, males from the group T + Sex expressed dysplasia in the dorsolateral prostate only, but not in the ventral prostate. Conclusions: These results indicate that constant copulation may facilitate the development of prostatic lesions in males with normal levels of testosterone. However, copulation induces less lesions in the ventral prostate of males treated with testosterone

Kinetics of proinflammatory cytokines after intraperitoneal injection of tribromoethanol and a tribromoethanol/xylazine combination in ICR mice

Tribromoethanol (2,2,2-tribromoethanol, TBE) is a popular injectable anesthetic agent used in mice in Korea. Our goal was to assess the risks associated with side effects (lesions) in the abdominal cavity, especially at high doses. To understand the underlying pathophysiological changes, we examined levels of cytokines through ELISA of abdominal lavage fluid and spleen collected from mice treated with low and high-dose TBE. ICR mice were anesthetized using one of the following protocols: a combination of TBE 200 mg/kg (1.25%) and xylazine 10 mg/kg; TBE 400 mg/kg (1.25%); and TBE 400 mg/kg (2.5%). Administration of high-dose TBE (400 mg/kg) increased the interleukin-1β and interleukin-6 levels in the peritoneal cavity over the short term (<1 day) compared with sham controls and low-dose TBE (200 mg/kg) groups. Cytokine expression in the low-dose TBE group was similar to the control group, whereas in the high-dose TBE group cytokine levels were higher in abdominal lavage fluid and spleen over the long term (10 days post-injection). We conclude that a combination of TBE 200 mg/kg (1.25%) and xylazine (10 mg/kg) is a safe and effective anesthetic for use in animals

The Neurobiology of Behavior and Its Applicability for Animal Welfare: A Review

Understanding the foundations of the neurobiology of behavior and well-being can help us better achieve animal welfare. Behavior is the expression of several physiological, endocrine, motor and emotional responses that are coordinated by the central nervous system from the processing of internal and external stimuli. In mammals, seven basic emotional systems have been described that when activated by the right stimuli evoke positive or negative innate responses that evolved to facilitate biological fitness. This review describes the process of how those neurobiological systems can directly influence animal welfare. We also describe examples of the interaction between primary (innate) and secondary (learned) processes that influence behavior

Cómo aprender a comportarse... sexualmente

A través del aprendizaje, los individuos pueden incrementar o disminuir de manera eficiente sus respuestas a estímulos internos (como las hormonas) o externos (señales del ambiente) que pueden desencadenar el deseo sexual e indicar quién es una pareja potencial para aparearse. Así mismo, el aprendizaje modifica el valor incentivo de las características de los individuos que se consideran atractivos o no. Esto ocurre principalmente a través de dos mecanismos: el condicionamiento Pavloviano y el Instrumental (operante). En el primero, los individuos aprenden a asociar estímulos neutros con respuestas incondicionadas, los cuales eventualmente se convierten en estímulos condicionados que predicen el evento sexual, y de manera inconsciente guían nuestras preferencias. En el segundo, los individuos aprenden a comportarse y a obtener una respuesta condicionada, lo cual pudiera explicar muchos rituales de cortejo en animales y humanos. En este artículo detallamos los efectos del aprendizaje desde la etapa perinatal hasta la edad adulta, haciendo énfasis en las etapas críticas en las cuales los individuos aprenden a comportarse sexualmente

The neuroscience of animal welfare: theory 80-20

Animal welfare is commonly regarded as the physical and psychological well-being of animals, fulfilled if animals are free: 1) from hunger, thirst and malnutrition, 2) from discomfort, 3) from pain, 4) to express normal behavior, and 5) from fear and distress. This paper is meant to provoke the reader to re-think the concept of welfare. Evidence indicates that animal welfare is not a constant state, but rather it must be fulfilled several times a day. A theory is proposed arguing that well-being occurs when the proportion of desiring and obtaining something occurs in a 80-20% proportion, respectively. The neurobiological bases of motivated behaviors are discussed to support a new view on animal welfare. Key words: Dopamine, Opioids, Environmental enrichment, Well-being, Desire, Reward.Comúnmente se considera al bienestar animal cuando los animales están bien física y psicológicamente. Esto se logra cuando están libres: 1) de hambre, sed y malnutrición, 2) de incomodidad, 3) de dolor, 4) para expresar conducta normal, 5) de miedo y estrés. Este artículo tiene la intención de provocar al lector para reconsiderar el concepto de bienestar animal. La evidencia indica que el bienestar no es un estado constante, sino que debe ocurrir muchas veces al día. Se propone una teoría con la que argumentamos que el bienestar ocurre cuando la proporción de desear algo y obtenerlo es del 80-20%, respectivamente. Se discuten algunas bases neurobiológicas de las conductas motivadas que apoyan la nueva visión de bienestar

The Sleep of Shelter Dogs Was Not Disrupted by Overnight Light Rather than Darkness in a Crossover Trial

Dogs in shelters may be unattended at night. The purpose of this study is to describe the night-time behavior of dogs in a shelter and to determine if artificial light affected their sleeping patterns. Ten dogs were video-recorded under both light and dark conditions and their behavior recorded using focal animal sampling. The dogs were lying down 649 ± 40 min (mean ± SD) in the light condition and 629 ± 58 min in the dark condition each night. They awoke, stood up, turned around and then lay down again every 48 to 50 min. There was no significant difference in time spent lying between the two conditions (p &gt; 0.05). Light did not seem to affect their behavior. The conclusion is that dogs in shelters may sleep in the absence of people and that light does not disrupt their sleep patterns