Chapter 1: Behavioral Endocrinology PDF

The Study of CHAPTER 1 Behavioral Endocrinology What is Behavioral Endocrinology What is Behavioral Endocrinology? Study of the interaction between hormones and behavior. Interaction is bidirectional: Hormones affect behavior. Behavior influences hormone levels. Ke...

The Study of CHAPTER 1 Behavioral Endocrinology What is Behavioral Endocrinology What is Behavioral Endocrinology? Study of the interaction between hormones and behavior. Interaction is bidirectional: Hormones affect behavior. Behavior influences hormone levels. Key Concepts: Hormones are chemical messengers affecting sensory systems, neural integration, and behavioral outputs. Environmental chemicals can mimic hormones, influencing behavior in humans and animals. Behavior isn’t limited to movement; outputs like color changes are also considered (e.g., chameleons and the Melanocyte-Stimulating Hormone [MSH])  Examples How Hormones Affect Behavior Example 1: Testosterone and Aggression Mechanism: Testosterone, produced by the testes (in males) and adrenal glands (in both sexes), can increase aggression by influencing brain regions like the amygdala and prefrontal cortex. Behavioral Outcome: Elevated testosterone levels in humans have been associated with heightened aggression, risk-taking, and competitive behaviors. Sensory System Involvement: Testosterone may heighten sensory sensitivity, such as visual or auditory processing of competitive cues, to prepare for social dominance interactions. Example 2: Oxytocin and Bonding Mechanism: Oxytocin, often called the "bonding hormone," is released by the posterior pituitary gland and acts on the limbic system, particularly the hypothalamus and amygdala. Behavioral Outcome: Oxytocin promotes trust, empathy, and bonding, particularly during childbirth, breastfeeding, and social interactions. Sensory System Involvement: During breastfeeding, tactile stimulation of the nipple signals the release of oxytocin, which strengthens mother-infant bonding and enhances caregiving behaviors. Examples How Behavior Affects Hormones Example 1: Exercise and Endorphins Mechanism: Physical activity stimulates the hypothalamus to release endorphins and signals the adrenal glands to release cortisol and adrenaline. Hormonal Outcome: Endorphins reduce stress and promote a feeling of well-being. Sensory System Involvement: Proprioceptive input from muscle movement informs the brain of physical exertion, triggering hormonal changes. Example 2: Social Stress and Cortisol Mechanism: Experiencing social rejection or competition activates the hypothalamus, leading to the release of corticotropin-releasing hormone (CRH) and subsequent cortisol secretion from the adrenal glands. Hormonal Outcome: Cortisol levels rise, increasing alertness and preparing the body to cope with stress. Sensory System Involvement: Sensory cues, like hearing someone’s tone of voice or seeing threatening facial expressions, can amplify stress responses and cortisol release.  Examples How Environmental Chemicals Mimic Hormones (Endocrine-disrupting chemicals [EDCs]) Example 1: Bisphenol A (BPA) Mechanism: BPA, found in plastics, mimics estrogen by binding to estrogen receptors. Behavioral Effect: BPA exposure has been linked to altered reproductive behaviors, including impaired mating preferences in both animals and humans. Sensory System Involvement: BPA’s effects on sensory systems may influence the detection of pheromones or other mating-related cues. Example 2: Polychlorinated Biphenyls (PCBs) Mechanism: PCBs mimic thyroid hormones and interfere with their signaling pathways. Behavioral Effect: PCB exposure during development has been linked to cognitive impairments and delayed sensory-motor integration in children. Sensory System Involvement: Thyroid hormone disruptions can impair the maturation of sensory systems like vision and hearing, affecting behavior. Historical Roots of Behavioral Endocrinology A Blend of Sciences: Combines methods from psychology, endocrinology, neuroscience, zoology, genetics, and more. Collaboration across fields helps us understand how hormones influence behavior. A Growing Field: Emerged as a distinct area of study in the mid-20th century. Key milestones: 1967: Launch of the journal Hormones and Behavior. 1996: Creation of the Society for Behavioral Neuroendocrinology. Historical Roots of Behavioral Endocrinology Aristotle’s detailed and accurate descriptions of castration effects laid the groundwork for early understandings of the relationship between biological structures, hormones, and behavior. 1. Physical Changes in Roosters: 1. Castrated roosters (capons) did not develop the typical physical traits of mature males, such as combs, wattles, or spurs. 2. They lacked the vibrant plumage and size associated with intact male roosters. 2. Behavioral Changes in Roosters: 1. Castrated roosters were less aggressive and did not engage in territorial fights or crowing, which are common behaviors in intact males. 2. They also showed reduced or no sexual behavior toward hens. 3. Effects on Humans: 1. Aristotle noted that castrated men (eunuchs) experienced physical changes, such as a lack of facial hair and a higher- pitched voice. https://youtu.be/KLjvfqnD0ws?feature=shared 2. He also observed a decrease in aggressive tendencies and sexual behavior compared to non-castrated men. 4. Broader Observations: 1. Aristotle concluded that the testes played a significant role in influencing both physical traits and behaviors associated with masculinity.  Historical Roots of Behavioral Endocrinology Berthold’s Experiment Introduction First formal study of endocrinology, conducted in 1849 by Arnold Adolph Berthold. Demonstrated that substances produced by the testes travel through the bloodstream to influence behavior. Marked the beginning of both endocrinology and behavioral endocrinology. Experiment Design Group 1: Both testes removed (castration). Result: Birds developed as capons with no crowing, mating, or aggression. Physical changes: Small bodies, pale and underdeveloped combs and wattles. Group 2: One testis reimplanted into the bird’s abdominal cavity. Result: Normal male development and behaviors (crowing, fighting, mating). Testis developed vascular connections and functioned normally. Berthold’s Experiment Impact and Legacy Revolutionary idea: Substances (hormones) can travel through the bloodstream to affect other parts of the body. Laid the foundation for the field of endocrinology and behavioral endocrinology. Initially overlooked—received no scientific attention for nearly 60 years. Inspired future research on the relationship between hormones and behavior. Why It Matters Showed that behavior could be influenced by internal biological processes. Highlighted the role of hormones in regulating mating, aggression, and physical development. Still referenced as a landmark study in behavioral endocrinology today.  What Are Hormones? The Discovery of Hormones In 1902, William Bayliss and Ernest Starling discovered a chemical messenger (later called secretin) in the duodenum that stimulated pancreatic secretions. Shifted understanding of regulation from the nervous system to chemical signaling. Experiment Key Findings: Bayliss and Starling’s work demonstrated that the secretion of digestive enzymes was triggered by a chemical signal from the intestine, rather than a direct neural signal. This work was pivotal in the identification of hormones as chemical messengers, marking the beginning of the field of endocrinology.  The Bayliss and Starling Experiment Overview of the Experiment: Bayliss and Starling's experiment sought to test the hypothesis that the digestive tract operates independently of signals from the brain. They used anesthetized dogs to explore how the digestive system responds to stimuli. Here’s a breakdown of the steps: Experiment 1: Procedure: They anesthetized a dog and exposed its small intestine, then severed the nerves leading to the intestine to prevent any signals from the brain and spinal cord from influencing the experiment. A solution of hydrochloric acid (HCl) was injected into the exposed section of the small intestine. They then collected pancreatic secretions (enzyme-rich fluids) from the pancreas, which were believed to be involved in digestion. Results: The data showed that, after the acid was injected, the pancreas released enzymes, regardless of any brain or nerve input. This demonstrated that the pancreas could be triggered by something in the intestine, not just from the brain or nervous system. This result suggested that a "secretory product," which was later termed a hormone, was involved in regulating pancreatic function. Experiment 2: In the second part of the experiment, Bayliss and Starling exposed another dog’s small intestine to HCl, but this time, they filtered out a substance from the tissue fluids of the intestine. They found that this filtrate also stimulated  What Are Hormones? Hormone Functions Hormones travel through the bloodstream (or tissue fluid in invertebrates) to target organs or tissues. Role in physiology and behavior: Regulate bodily functions (e.g., metabolism, reproduction). Coordinate physiological changes with behaviors like mating and activity. Example: Hormones promoting gamete maturation also trigger mating behavior. Hormonal Regulation of Behavior Example: Metabolic hormones elevate blood glucose levels before waking, anticipating energy needs. Not all cells are influenced by every hormone. A hormone can only Ensures physiology and behavior are synchronized with environmental directly influence demands. cells that have specific receptors for that hormone. Cells with the Comparison to Neurotransmitters specific receptors for a hormone are called target cells. The interaction between a Differences: hormone and its Hormones act over longer distances and timeframes. receptor initiates a series of cellular events. These events can lead to Neurotransmitters work rapidly and locally. the activation of cellular pathways or gene expression and protein synthesis. Newly  Hormonal or Physiological Example Function/Role Process Prepares the body for 'fight or Adrenaline release during flight' by increasing heart rate, Adrenaline (epinephrine) stressful situations dilating pupils, and boosting energy. Signals the body to prepare for Melatonin production at night Melatonin sleep, aligning the circadian rhythm with the day-night cycle. Helps cells absorb glucose from Insulin release after eating Insulin the bloodstream for energy, regulating blood sugar levels. Reduces pain and increases Endorphin release during Endorphins pleasure, promoting continued exercise physical activity. Oxytocin release during Promotes feelings of trust, bonding activities (e.g., Oxytocin affection, and bonding, supporting hugging or childbirth) social behaviors like attachment. The Study of Behavior Behavioral Endocrinologists' Focus: Study how hormones alter the development and expression of behavior. Explore how behavior may influence hormone levels. Key Components of Animal Behavior The three components Input Systems: Sensory systems that detect environmental stimuli. Integrators: The central nervous system (CNS) processes and integrates sensory input. Output Systems: Effectors (e.g., muscles) that produce behavioral responses. Hormones’ Role: Hormones do not directly cause behavioral changes but influence the likelihood of specific behaviors being elicited. Hormones modify the probability that a behavior will occur in response to appropriate stimuli. The influence of hormones is not about causing behavior but making it more likely in the correct situation. Estrogens’ Potential Effects on Zebra Finch Singing Zebra Finch Singing: Only male zebra finches sing in nature. Testosterone and Estrogen’s Role: Removing the testes reduces singing behavior. Reimplanting testes or providing testosterone or estrogen (estradiol) restores singing behavior. Estrogens, likely derived from testosterone, influence singing. Hormonal Influence on Behavior: Estrogen levels are highest when singing behavior is most frequent. Sensory Capabilities: Estrogens might enhance the bird's ability to detect relevant environmental stimuli. Central Nervous System (CNS): Estrogens may affect the neural architecture, improving the processing of sensory inputs. Changes in motivation, attention, and perception could also be influenced. Effector Organs: Estrogens could influence the muscles controlling vocalization (e.g., syrinx), thus affecting singing behavior. Human Aggression Sensory Capabilities: Testosterone may heighten sensitivity to certain stimuli, making a person more likely to perceive threats or challenges as aggressive cues. Central Nervous System (CNS): Testosterone can impact brain areas associated with aggression, such as the amygdala, influencing emotional responses and decision-making. It may also enhance the motivation to assert dominance or compete, increasing the likelihood of aggressive behavior. Effector Organs: Testosterone may affect muscle tone or increase physical readiness for aggressive action (e.g., posture, facial expressions, vocalizations).  How Might Behavior Affect Hormones? Behavior Hormones Affected How Behavior Affects Hormones Mechanism Testosterone, Growth Exercise increases testosterone and growth hormone, Physical exertion activates stress responses, prompting Physical Exercise Hormone, Endorphins and releases endorphins. hormone changes to support recovery. Seeking emotional support can reduce cortisol and Positive social interactions activate the Social Support Oxytocin, Cortisol increase oxytocin. parasympathetic nervous system, reducing stress. Caring for or bonding with a baby increases oxytocin Emotional and physical interaction with the baby Parenting Behavior Oxytocin, Prolactin and prolactin, supporting bonding and milk production. activates hormone production. Competition (Winning Social challenge activates hormonal changes related to Testosterone Winning increases testosterone, while losing reduces it. or Losing) dominance and stress. Emotional Expression Crying or expressing emotions reduces cortisol and Emotional release reduces the stress response and Cortisol, Oxytocin (Crying, Sadness) increases oxytocin. promotes bonding. Social rejection is perceived as a threat, triggering the Social Exclusion Cortisol Social exclusion increases cortisol, indicating stress. body’s stress response. Romantic Interaction Physical touch such as hugging or kissing increases Intimacy stimulates the release of oxytocin, enhancing Oxytocin (Physical Touch) oxytocin, promoting feelings of trust and bonding. emotional connection. Mindfulness reduces stress by activating the Meditation reduces cortisol levels and increases Meditation Cortisol, Serotonin parasympathetic nervous system, promoting serotonin. relaxation. Laughter stimulates the brain’s reward system and Laughter Endorphins, Cortisol Laughter increases endorphins and decreases cortisol. reduces stress levels. Mindset (Growth vs. Adopting a growth mindset reduces cortisol and A positive mindset reduces stress and fosters feelings Cortisol, Testosterone Fixed Mindset) increases testosterone in response to challenges. of competence, increasing testosterone. Common Techniques in Behavioral Endocrinology Technique Description Purpose Example To observe the effects of hormone Removing the testes in male birds and replacing Removal of a gland suspected of producing a hormone, Ablation and Replacement removal and replacement, helping to them with testosterone to study their role in followed by replacement with the hormone or gland. determine the hormone’s role. singing behavior. Radioimmunoassay (RIA) to measure hormone A technique using antibodies to measure the presence To precisely measure hormone levels in Immunoassays levels, such as cortisol or testosterone, in various and concentration of hormones in a sample. blood, saliva, or other fluids. samples. Enzyme Immunoassay A type of immunoassay that uses enzymes to detect To measure hormones non-radioactively Home pregnancy tests (ELISA) measure human (EIA) hormones, often providing quantitative results. and in a quantifiable manner. chorionic gonadotropin (hCG) levels in urine. To study hormone levels without Noninvasive Hormone Using fluids like saliva, feces, or hair to measure Measuring cortisol levels in saliva to avoid disturbing the subject through invasive Measurement hormone concentrations without drawing blood. disturbing animals in field studies. procedures. Immunocytochemistry To study the localization of hormones or Using antibodies to detect hormone receptors or Detecting estrogen receptors in the brain to study (ICC)/Immunohistochemist hormone receptors in tissues, especially hormones in cells or tissues. its effects on behavior. ry (IHC) in the brain. Tissue is homogenized and proteins/nucleic acids Blot Tests (Southern, To determine the presence of specific Western blot to detect specific proteins like separated via electrophoresis, then transferred to a Northern, Western) proteins or nucleic acids in tissue. hormone receptors or enzymes in brain tissue. membrane to be detected using labeled tracers. Tissue is fixed, sliced, and hybridized with a Detecting the mRNA for a specific hormone in To identify cells or tissues producing a In Situ Hybridization radiolabeled cDNA probe to locate mRNA encoding brain tissue using radiolabeled probes to identify specific protein by detecting mRNA. specific proteins. gene expression. Inserting hollow electrodes or fine tubes (cannulas) into To manipulate or measure substances at Injecting testosterone into the preoptic area of the Cannulation specific brain areas or blood vessels to introduce specific brain sites or correlate hormone hypothalamus in male rats to study sexual substances or sample blood. levels with behavior. behavior. Connecting the circulatory systems of two animals to To study the effects of hormones in one Connecting the circulatory systems of two rats to Parabiosis observe the effects of one animal's endocrine system animal on another by sharing their blood study the behavioral effects of one rat’s hormone on the other's behavior. systems. levels on the other. Inactivating or overexpressing a specific gene, To study the behavioral effects of specific Creating knockout mice lacking the estrogen Genetic Manipulations including hormone-related genes, to observe its effect genes encoding hormones or hormone receptor to study the role of estrogen in (Transgenic/Knockout) on behavior. receptors. reproductive behavior. Involves the use of small electrodes placed near Recording the activity of neurons in the Electrical Recording To uncover the direct effects of hormones neurons to monitor changes in neural activity in hypothalamus after hormone exposure to study (Single-Unit) on neural activity. response to hormonal exposure. neural responses to estrogen. A technique where fine electrodes are positioned in the To study the causal effects of hormones Stimulating the hypothalamus with weak Electrical Stimulation brain to stimulate neurons, revealing the effects of on neural activity and behavior by electrical currents to explore how it affects hormones on neural circuits. stimulating specific neurons. behavior in response to hormonal signals. A technique that uses light to control the activity of To control and study neural activity with Using optogenetics to activate specific neurons in Optogenetics neurons that express light-sensitive ion channels, high precision, linking hormonal influence the brain and observing changes in behavior in allowing precise neural manipulation. to behavior. response to hormones like oxytocin.