In his research titled “Astrocytes in the Rat Medial Amygdala are Responsive to Adult Androgens” (Breedlove et al., 2012) Breedlove evidently shows that the posterodorsal medial amygdala (MePD) has various sex differences. This entails variations in the volume and number of morphology that makes its neurons and atroctyes. In adulthood, gonadal hormones that include androgens and estrogens play an important role in maintaining the masculine character of various sex differences. Nevertheless, during adulthood gonadal hormones are involved in maintaining the number and complexities involved in astrocytes, especially in the male MePD. This research was done through examination of astrocytes in the MePD of both sexes. The rats were gonadectomized and treated for 30 days with testosterone. A control experiment was also conducted for comparison. After the experiment was complete, brains were collected and immunostained for glial fibrillary acidic protein. Through the stereological analysis it was noted that androgen levels were influenced by the number and complexities of astrocytes in the MePD in both males and females. However, specific effects of the androgens were different in both sexes. On the same, it was evident that sex differences in both the number and complexity of adult astrocytes were more persistent even when gonadal hormones were absent in adult rats. This suggested that the androgens are also active in the early stages of life development. This helps determine adult differences in terms of sex. It was also evident that testosterone may also act directly on MePD astrocytes. Hence, they influence their structure and function.
Breedlove et al. (2002) carried out an empirical research titled “Evidence that Androgen Acts through NMDA Receptors to Affect Motoneurons in the Rat Spinal Nucleus of the Bulbocavernosus”. From the research, it was found that in adult males, spinal nucleus of the bulbocavernosus (SNB) motoneurons has the capacity to shrink soon after castration. In order to establishes this, 60 old Spraque Dawley male rats were castrated and implanted with Silastic capsules that contained testosterone (T) and asmotic minipumps that were infused in MK-801 that is a non competitive NMDA receptor antagonist. After 20 days bulbocavernosus muscles were also injected with retrograde tracer cholera toxin-horseradish peroxidase conjugate (CT-HRP. From the experiment, it was evident that castration reduced expression of receptors in SNB motoneurons. This effect was, however, blocked by androgen replacement in castrates. On the same, manipulation of androgens did not have any effect on expression of NMDA receptor subtypes that was present in RDLN mononeurons. These results suggest that androgens have the ability to influence the size of SNB motoneurons by first influencing their expression in the NMDA receptor. As a result, the response of the motoneurons to andogenous glutamate is highly affected by androgens.
In 1992, Breedlove gonadectomized adult male rats to determine whether androgen locally regulates rat bulbocavernosus and levator ani size. After gonadectomizing the rats, small silastic capsules were filled with hormones until saturation. This was done to each bulbocavernosus and levator ani muscle complex (BC/LA). In order to come up with accurate result, two experiments were conducted. In the first experiment, one capsule contained testosterone (T). The capsule in the other experiment contained contralateral muscles with antiandrogen hydroxyflutamide (hFl). This treatment was important to ensure that proper focus of androgenic stimulation of the muscles were on one side. This was left for 30 days where rats were sacrificed and the BC/LA muscle pairs removed. The muscles were also weighed and compared. The BC/LA muscle pairs exposed to treatment that contained testosterone (T) were heavier than those in the other experiment that contained antiandrogen hydroxyflutamide (hFl). Their weight difference was about 12 percent. On the same, muscle fibers in T-treatment BCs were observed to be larger than those in the hF1 treatment, where the BCs were larger in diameter than those in the contralateral. These results indicated that androgen has the capacity to exert its anabolic effect as it acts locally on a cell population within or near BC/LA. To ensure the results were more accurate, the hF1 and black capsules were implanted in castrated males. In this case, the hF1 muscles were treated. It was noted that they were heavier by 9 percent. This was a clear demonstration of the effects of anabolic of hF1, especially when androgen was absent. However, this refuted the idea that hF1 was responsible for causing the toxic effects in the first experiment. As evident from the results, gonadectomized rats used in the T experiment in comparison to those used in hF1 experiment were about 8 percent heavier. The concept of differences in muscle weights was also compared in animals that were made to receive the bilateral denervation of the BC/LA. It was also noted that at the time of capsule implantation of testosterone (T) and antiandrogen hydroxyflutamide (hFl), local testosterone treatment failed to show any changes in the weights of BC/La in the denevated muscles. This effect was also seen in the gonadectomy process.
According to Breedlove et al (1982), there is a sexual dimorphic motor nucleus in the fifth and sixth lumbar segments of the rat spinal cord, especially in the spinal nucleus of the bulbocavernosus (SNB). There is a common difference in the dorsolateral nuceus (DLN) that is found in the ventral horn of rat's lumbar cord. This mainly includes rat mononeurons innervating of the ischiocavernosus muscle as well as in the dimorphic perinealmuscle. On the other hand, adult females have fewer motoneurons in the DLN. This is associated with the fact that there is normally absence of neurons innervating the ischiocavernosus muscle that is not found among female rats. The research also established that after sometime, the effect of single dose was evident in that their life was confined to certain rostrocaudal regions. This phenomenon was common among adult rats. These regions were partially masculine, which closely related to the female DLN. It is worthy to note that the research established that masculine females have more DLN neurons, which is not the case in other females. The change in DLN neurons is in line with the hypothesis that androgens are usually involved in the dimorphic development of DLN. On the other hand, there is small difference in retrodorsolateral nucleus, where their study showed that DLN also influence their development. For instance, in motor nucleus the difference in terms of retrodorsolateral nucleus is also evident.
In four empirical researches Breedlove focuses on the topic of behavioral and cognitive neuroscience in animals putting a major focus on rats. He employs various techniques that make it possible to integrate other related aspects in these four researches. These writings are based on researches and experiments that are developed after conducting research in the field of behavioral neuroscience. Breedlove's aim is to study, analyze, and interpret various phenomena in relation to the topic of study. This implies that he aims to study behavioral and cognitive neuroscience and other related body processes in animals as well as to make more discoveries to support or refute previous knowledge or theories in the same field. He carried out an in-depth research in this area in order to come up with accurate and detailed information using biologically based theories and approaches. He engaged other researchers, who helped enrich findings of the entire study. It is also evident from the writings that Breedlove helps learners understand even the most complex topics in animals such as in rats. This is achieved by conducting well-designed experiments with 10 years between each research. For example, it is easy to relate four writings despite the fact that they have been written at different times. The relationship is possible because Breedlove specializes in a single area of behavioral neuroscience that is also known as biological psychology in rats. This provides relevant and in-depth analysis of information, making it possible to identify some areas that have not been covered. Although Breedlove and his co-authors do not present an entirely exhaustive research in all areas of behavioral neuroscience, they try to study some of the most important areas that keep on changing in animals, especially in rats.
Breedlove does not directly apply theories in his research, although he uses various hypotheses in carrying and analyzing his researches. Some of these hypotheses include the following: poster dorsal medial amygdala (MePD) has various sex differences, which entails variations in the volume and the number of morphology that gives its neurons and atroctyes, and the spinal nucleus of the bulbocavernosus (SNB) motoneurons the capacity to shrink as well as there is a sexual dimorphic motor nucleus in the fifth and sixth lumbar segments of rat's spinal cord.
Researcher’s theoretical and hypothetical foundation changes from one research to another to the extent that the compilation of various experiments results in a critical analysis of the chosen topic. From the articles it is evident that Breedlove does not use the same titles, although he covers similar areas using different approaches. This enables him to answer some of the unanswered questions as well as to address limitations associated with previous research. For example, he addresses the following areas: astrocytes in the rat medial amygdala are responsive to adult androgens, evidence that androgen acts through NMDA receptors to affect motoneurons in the rat spinal nucleus of the bulbocavernosus, androgen locally regulates rat bulbocavernosus and levator ani size as well as sexual dimorphism and the influence of neonatal androgen in the dorsolateral motor nucleus of the rat lumbar spinal cord (Breedlove et al., 2010). This evidently shows the relationship between topics increasing understanding of learners about experiments and resultant findings.
Breedlove works with various authors in his empirical researches. They carry the research together since all of them are knowledgeable in the same field of neuroscience. Some of these researchers include Johnson, Schneider, DonCarlos, Jordan, Christensen, Handa, Anderson, Pouliot, Rand, Jordan, and Arnold. These scientists contribute to the research as they are professionals in the same field. As a result, they contribute to these empirical studies in which Breedlove is the key researcher.
In conclusion, Breedlove’s empirical researches form the basis in the field of behavioral neuroscience and related processes. His findings can be applied in various instances, even to study body processes in human beings. They play an important role in enriching the field through laboratory experiments. In addition, the results from these experiments are used as controls in other experiments.
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