The influence of bilateral neonatal lesions of the amygdala on pubertal onset and sexual behavior in female Rhesus Macaques living in social groups 公开

Stephens, Shannon Brooke Zoe (2013)

Permanent URL: https://etd.library.emory.edu/concern/etds/s4655h302?locale=zh
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Abstract

Reproduction is regulated by various physiological and environmental factors, one of which is social context. Delayed first ovulation is observed in lower-ranking female rhesus macaques, in comparison to higher-ranking females, and lower-ranking females show a tight coupling of estradiol levels and sexual behavior in social groups (Zehr et al., 2005; Wallen, 1990). The brain mechanisms modulating the effects of social context on puberty onset and sexual behavior are unknown. The amygdala is one potential region of the brain modulating the effects of social context on reproduction because of its importance for behavioral responses to social information (Thompson et al., 1969; Spiteri et al., 2010) as well as its connections to the hypothalamus (Amaral et al., 1992). We examined the effects of neonatal bilateral neurotoxic amygdala lesions on pubertal timing and sexual behavior in female rhesus macaques living in social groups. At one month of age, subjects received either bilateral amygdala lesions or a sham-operated procedure. Beginning in August, 14-17 months of age, vaginal swabs and blood samples were collected to assess the age at menarche and first ovulation. Sexual behavior was examined in a pair test and in the social group. Earlier menarche and first ovulation were observed in lesioned females in comparison to control females. Based on the current study, it is not clear what, if any, effect the amygdala has on modulating social information that alters the timing of puberty. Lesioned females showed lower levels of some female-initiated sexual behaviors in the social group observations, but there was no effect of amygdala lesions on female sexual receptivity. Estradiol did not influence the rate of behavior observed in lesioned females, though some effects were observed in control females. The mechanisms by which the amygdala alters puberty onset and sexual behavior are unknown. It is possible that puberty onset occurred earlier in lesioned females as a result of earlier removal of GABA inhibition on GnRH release, resulting in earlier menarche and ultimately, earlier first ovulation. Sexual behavior differences in amygdala-lesioned females may result from decreased estradiol sensitivity, thereby influencing the modulatory relationship that estradiol can have on female sexual behavior.


Table of Contents

Table of Contents

Chapter 1: General Introduction...................................................................................... 1

Neuroanatomy of the Hypothalamus and the Amygdala................................. 12

The Effect of the Amygdala on Female Sexual Behavior................................ 14

Hormonal Regulation in Adult Females............................................................. 29

Specific Aims and Hypotheses............................................................................ 56

Figure Captions.................................................................................................... 58

Figure 1................................................................................................................. 59

Figure 2................................................................................................................. 60

Figure 3................................................................................................................. 61

Figure 4................................................................................................................. 62

Figure 5................................................................................................................. 63

Figure 6................................................................................................................. 64

Chapter 2: Environmental and social influences on neuroendocrine puberty and

behavior in macaques and other nonhuman primates................................................. 65

(Note: Chapter 2 discusses both males and females, but this dissertation is focused on females)

Abstract................................................................................................................ 66

Puberty Onset....................................................................................................... 69

Seasonal Influences on Puberty Onset............................................................... 74

Body Weight and Puberty Onset........................................................................ 79

Social Rank and Puberty Onset.......................................................................... 87

Pre-and Neonatal Testosterone Levels and Puberty Onset.............................. 99

Pubertal Changes in Behavior.......................................................................... 105

Conclusion.......................................................................................................... 113

Acknowledgements............................................................................................ 115

References.......................................................................................................... 116

Figure Captions.................................................................................................. 131

Figure 1............................................................................................................... 132

Figure 2............................................................................................................... 133

Figure 3............................................................................................................... 134

Chapter 3: Neonatal Amygdala Lesions Advance Pubertal Timing in

Female Rhesus Macaques............................................................................................. 135

Abstract.............................................................................................................. 136

Introduction........................................................................................................ 137

Method................................................................................................................ 140

Results................................................................................................................. 149

Discussion........................................................................................................... 154

Acknowledgements............................................................................................ 159

References.......................................................................................................... 160

Table 1................................................................................................................ 166

Figure Captions.................................................................................................. 167

Figure 1.............................................................................................................. 168

Figure 2.............................................................................................................. 169

Figure 3.............................................................................................................. 170

Figure 4.............................................................................................................. 171

Figure 5.............................................................................................................. 172

Figure 6.............................................................................................................. 173

Figure 7.............................................................................................................. 174

Chapter 4: Effects of Neonatal Amygdala Lesions and Social Context on

Sexual Behavior in Female Rhesus Macaques............................................................ 175

Abstract............................................................................................................. 176

Introduction....................................................................................................... 178

Method............................................................................................................... 181

Results................................................................................................................ 189

Discussion.......................................................................................................... 200

Acknowledgements........................................................................................... 207

References......................................................................................................... 208

Table 1............................................................................................................... 212

Table 2............................................................................................................... 213

Table 3............................................................................................................... 215

Table 4............................................................................................................... 218

Figure Captions................................................................................................. 221

Figure 1.............................................................................................................. 222

Figure 2.............................................................................................................. 223

Figure 3.............................................................................................................. 224

Figure 4.............................................................................................................. 225

General Discussion......................................................................................................... 226

Does the amygdala influence the timing of puberty?..................................... 228

Does the amygdala eliminate the effects of social rank

on pubertal timing?.................................................................................... 232

Does the amygdala influence sexual behavior and how do these

effects differ based on the social context?................................................ 233

Conclusions........................................................................................................ 237

General Introduction and Discussion References.......................................... 239


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