Today's Topics

Hormones

  • Chemicals secreted into blood
  • Act on specific target tissues via receptors
  • Produce specific effects

Examples of substances that are both hormones and NTs

  • Melatonin
  • Epinephrine/adrenaline
  • Oxytocin
  • Vasopressin

Behaviors under hormonal influence

  • Ingestive (eating/ drinking)
    • Fluid levels
    • Na, K, Ca levels
    • Digestion
    • Blood glucose levels

Behaviors under hormonal influence

  • Reproduction
    • Sexual Maturation
    • Mating
    • Birth
    • Care giving

Behaviors under hormonal influence

  • Responses to threat/ challenge
    • Metabolism
    • Heart rate, blood pressure
    • Digestion
    • Arousal

What do these behaviors have in common?

  • Biological imperatives
  • Proscribed in space and time
  • Foraging/hunting
    • Find targets distributed in space, evaluate, act upon
  • Often involve others

Principles of hormonal action

  • Gradual action
  • Change intensity or probability of behavior
  • Behavior influences/influenced by hormones
    • +/- Feedback
  • Multiple effects on different tissues

Principles of hormonal action

  • Produced in small amounts; released in bursts
  • Levels vary daily, seasonally
    • or are triggered by specific external/internal events
  • Effect cellular metabolism
  • Influence only cells with receptors

Differences between neural and hormonal communication

  • Point to point vs.“broadcast”
    • Wider broadcast than neuromodulators
  • Fast vs. slow-acting
  • Short-acting vs. long-acting
  • Digital (yes-no) vs. analog (graded)
  • Voluntary control vs. involuntary

Similarities between neural and hormonal communication

  • Chemical messengers stored for later release
  • Release follows stimulation
  • Action depends on specific receptors
  • 2nd messenger systems common

Where are hormones released

Where are hormones released?

  • CNS
    • Hypothalamus
    • Pituitary
      • Anterior
      • Posterior
    • Pineal gland

Where are hormones released

Where are hormones released?

  • Rest of body
    • Thyroid
    • Adrenal (ad=adjacent, renal=kidney) gland
      • Adrenal cortex
      • Adrenal medulla
    • Gonads (testes/ovaries)

Two release systems

  • Direct
  • Indirect

Direct hormone release into bloodstream

  • Hypothalamus (paraventricular, supraoptic nucleus) to
  • Posterior pituitary
    • Oxytocin
    • Arginine Vasopressin (AVP, vasopressin)

Direct release

Indirect release

  • Hypothalamus -> releasing hormones
  • Anterior pituitary -> tropic hormones
  • End organs

Indirect release

Case studies

Case 1: Responses to threat or challenge

  • Neural response
    • Sympathetic Adrenal Medulla (SAM) response
    • Sympathetic NS activation of adrenal medulla, other organs
    • Releases NE and Epi

(Ulrich-Lai & Herman, 2009)

Case 1: Responses to threat or challenge

  • Endocrine response
    • Hypothalamic Pituitary Adrenal (HPA) axis
    • Adrenal hormones released
  • Hypothalamus
    • Corticotropin Releasing Hormone (CRH)
  • Anterior pituitary
    • Adrenocorticotropic hormone (ACTH)

Case 1: Responses to threat or challenge

  • Adrenal cortex
    • Glucocorticoids (e.g., cortisol)
    • Mineralocorticoids (e.g. aldosterone)

Adrenal hormones

  • Steroids
    • Derived from cholesterol
  • Cortisol
    • increases blood glucose, anti-inflammatory effects
    • negative consequences of prolonged exposure
  • Aldosterone
    • Regulates Na (and water)

Case 2: Reproductive behavior – the milk letdown reflex

  • Supraoptic & Paraventricular nucleus (PVN) of hypothalamus releases oxytocin
    • Into bloodstream via posterior pituitary (endocrine)
    • Onto neurons in nucleus accumbens (neurocrine), amygdala, brainstem

Milk letdown reflex

Oxytocin's role

Oxytocin

Melatonin

  • Diurnal rhythm
  • Night time peak, early morning low
  • Secretion suppressed by "blue" light (< 460-480 nm)
  • Rhythm irregular until ~3 mos post-natal (Ardura, Gutierrez, Andres, & Agapito, 2003)
  • Peak weakens, broadens with age

Melatonin circuitry

  • Suprachiasmatic nucleus of the hypothalamus
  • Paraventricular nucleus of the hypothalamus
  • Spinal cord
  • Superior cervical ganglion
  • Pineal gland

How to think about neurochemical influences

  • Measure hormones in blood, saliva; can't effectively measure NTs
  • Multivariate, nonlinear, mutually interacting
  • Varied time scales
    • Phasic (e.g., cortisol in response to challenge)
    • Periodic (e.g., melatonin; diurnal cortisol)

How to think about neurochemical influences

  • Peripheral effects + neural feedback
  • State variables and behavior
    • Are your participants sleepy, hungry, horny, distressed…
    • Endogenous & exogenous influences

Sarkar, A., et al. (2016). Trends in Neurosciences, 39(11), 763–781.

Next time…

  • How the human brain got this way…

References

Ardura, J., Gutierrez, R., Andres, J., & Agapito, T. (2003). Emergence and evolution of the circadian rhythm of melatonin in children. Horm. Res., 59(2), 66–72. https://doi.org/68571

Domes, G., Heinrichs, M., Kumbier, E., Grossmann, A., Hauenstein, K., & Herpertz, S. C. (2013). Effects of intranasal oxytocin on the neural basis of face processing in autism spectrum disorder. Biological Psychiatry, 74(3), 164–171. https://doi.org/http://dx.doi.org/10.1016/j.biopsych.2013.02.007

Ulrich-Lai, Y. M., & Herman, J. P. (2009). Neural regulation of endocrine and autonomic stress responses. Nature Reviews Neuroscience, 10(6), 397–409. https://doi.org/10.1038/nrn2647

Viviani, D., Charlet, A., Burg, E. van den, Robinet, C., Hurni, N., Abatis, M., … Stoop, R. (2011). Oxytocin selectively gates fear responses through distinct outputs from the central amygdala. Science, 333(6038), 104–107. https://doi.org/10.1126/science.1201043

Weisman, O., & Feldman, R. (2013). Oxytocin effects on the human brain: Findings, questions, and future directions. Biological Psychiatry, 74(3), 158–159. https://doi.org/http://dx.doi.org/10.1016/j.biopsych.2013.05.026