3.3 Neurotransmitter-hormone interactions in motivation
4 min read•august 1, 2024
Neurotransmitters and hormones team up to control our behaviors and emotions. They work together in complex ways, influencing everything from hunger to stress responses. Understanding these interactions helps explain why we feel and act the way we do.
This teamwork is crucial for adapting to our environment. For example, stress hormones and brain chemicals coordinate to help us deal with threats. Meanwhile, appetite-related hormones interact with brain signals to regulate eating. It's a delicate dance that keeps us in balance.
Neurotransmitters and Hormones in Motivation
Synergistic Regulation of Motivated Behaviors
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Neurotransmitters and hormones work synergistically to regulate motivated behaviors (feeding, mating, stress responses)
Hypothalamic-pituitary-adrenal (HPA) axis demonstrates complex interactions between neurotransmitters and hormones in stress-related motivated behaviors
and interact with and to modulate reward-seeking behaviors and social bonding
Mesolimbic dopamine system interacts with gonadal hormones to influence sexual motivation and behavior
and interact with hypothalamic neurotransmitters to regulate feeding behavior
Ghrelin stimulates appetite and food intake
Leptin suppresses appetite and promotes feelings of fullness
Neurotransmitter-hormone interactions exhibit plasticity, allowing for adaptive changes in motivated behaviors
Adapts to environmental demands (food availability, social pressures)
Responds to internal states (energy balance, reproductive status)
Examples of Neurotransmitter-Hormone Interactions
(CRH) released by hypothalamus
Stimulates (ACTH) release from pituitary
ACTH triggers cortisol release from adrenal glands
Cortisol provides negative feedback to hypothalamus and pituitary
Reproductive behavior
Gonadotropin-releasing hormone (GnRH) from hypothalamus stimulates (FSH) and (LH) release
FSH and LH regulate production of and
These sex hormones influence dopamine release in reward centers, affecting sexual motivation
Feeding behavior
(NPY) in hypothalamus stimulates feeding
Interacts with leptin, which inhibits NPY neurons
Ghrelin enhances NPY activity, promoting hunger
Brain-Endocrine System Feedback Loops
Hypothalamic-Pituitary Axis
Hypothalamus serves as primary interface between nervous and endocrine systems
Integrates neural and hormonal signals
forms basis for multiple neuroendocrine feedback loops
HPA axis (stress response)
HPG axis (reproductive function)
HPT axis (thyroid function)
Negative feedback loops maintain
Inhibit further hormone release when target levels reached
Example: Cortisol inhibits further CRH and ACTH release in HPA axis
Positive feedback loops amplify hormonal responses in certain physiological processes
Example: Oxytocin-mediated milk let-down reflex during breastfeeding
Circadian Rhythm and Hormone Regulation
Circadian rhythm regulated by suprachiasmatic nucleus influences timing of hormone release and neurotransmitter activity
secretion peaks at night, promoting sleep
Cortisol levels highest in morning, promoting wakefulness
Neurotransmitters act as neurohormones when released into bloodstream
Provides additional communication between brain and endocrine system
Example: released from sympathetic neurons acts on distant target organs
Hormone receptors in brain allow direct modulation of neural activity by circulating hormones
Completes feedback loop between endocrine and nervous systems
Example: Estrogen receptors in hypothalamus influence GnRH release
Neurotransmitter Modulation of Hormones
Direct and Indirect Hormone Regulation
Neurotransmitters directly stimulate or inhibit hormone-producing cells in endocrine glands
Example: Dopamine inhibits prolactin release from anterior pituitary
Release of hypothalamic releasing and inhibiting factors controlled by various neurotransmitters
(TRH) release stimulated by norepinephrine
(GHRH) release influenced by serotonin
modulate release of stress hormones from adrenal glands
Norepinephrine and stimulate cortisol and aldosterone release
Serotonin influences release of growth hormone and prolactin from anterior pituitary
Enhances growth hormone release
Inhibits prolactin release
Neurotransmitter Effects on Hormone Sensitivity
and in hypothalamus regulate release of gonadotropin-releasing hormone (GnRH)
GABA inhibits GnRH release
Glutamate stimulates GnRH release
Neurotransmitters alter sensitivity of target tissues to hormones
Modulate receptor expression
Influence intracellular signaling pathways
Example: Norepinephrine enhances adipose tissue sensitivity to lipolytic hormones
Autonomic nervous system rapidly modulates hormone release from various endocrine glands
Sympathetic stimulation increases epinephrine release from adrenal medulla
Parasympathetic stimulation enhances insulin release from pancreas
Hormones in Neurotransmitter Regulation
Steroid and Thyroid Hormone Effects
Steroid hormones influence synthesis, release, and reuptake of neurotransmitters in specific brain regions
Estrogen enhances serotonin synthesis and decreases its reuptake
Testosterone modulates dopamine release in reward centers
Thyroid hormones modulate activity of catecholamine neurotransmitters
Affects mood and cognitive function
Hypothyroidism associated with decreased norepinephrine activity
interact with serotonergic system
Potentially contributes to stress-related mood disorders
Chronic stress and elevated cortisol linked to decreased serotonin function
Neuropeptides and Circadian Influences
Oxytocin and influence social behavior by modulating dopamine and serotonin release
Enhance dopamine release in nucleus accumbens during social bonding
Modulate serotonin activity in amygdala, affecting emotional processing
Melatonin affects activity of various neurotransmitter systems
Enhances GABA activity, promoting sleep
Modulates serotonin release, influencing mood and circadian rhythms
Hormones alter neurotransmitter receptor expression and sensitivity
Estrogen increases serotonin receptor density in certain brain regions