Endorphins
Endorphins play a role in blocking Pain Perception and are secreted in response to exercise (helping to account for the famed “runner’s high” or “endorphin high” that hits many hardy joggers around the 30-minute mark). (Location 2044)
🤖 AI addition (15/06/26):
What Are Endorphins?
“Endorphins” is shorthand for endogenous opioids — a family of neuropeptides that act on opioid receptors in the CNS and periphery. The family includes:
Peptide Precursor Primary Receptor Main Sites β-Endorphin POMC μ (mu) Hypothalamus, pituitary, PAG Enkephalins (Met-, Leu-) Proenkephalin δ (delta) Striatum, spinal cord Dynorphins Prodynorphin κ (kappa) Striatum, spinal cord, hypothalamus
POMC (pro-opiomelanocortin) is the large precursor peptide that gets cleaved to yield β-endorphin, ACTH, α-MSH, and other bioactive fragmentsPOMC Precursor
POMC (pro-opiomelanocortin) is synthesized in the arcuate nucleus of the hypothalamus and in the anterior pituitary. Post-translational cleavage produces:
- β-Endorphin — potent opioid, 31 amino acids
- ACTH — adrenal corticotropin (stress response — see CRH)
- α-MSH — melanocyte-stimulating hormone, regulates pigmentation and appetite
This means stress (via CRH → ACTH) and opioid analgesia are biochemically linked through the same precursor.
Pain Modulation
Endorphins suppress Pain Perception via two main mechanisms:
- Gate control at spinal cord: Enkephalins in the dorsal horn inhibit incoming pain signals at the first synapse (presynaptic inhibition of substance P release).
- Descending inhibition: β-Endorphin activates neurons in the periaqueductal gray (PAG) → inhibits spinal pain relay neurons via serotonin and norepinephrine pathways.
μ-opioid receptor activation → Gi protein coupling → ↓ cAMP, ↑ K⁺ conductance (hyperpolarization), ↓ Ca²⁺ → reduced neuronal excitability.
Social Pain = Physical Pain
A striking finding: the same opioid system mediates both physical pain and social pain (rejection, exclusion, loss). Opioid receptors in the anterior cingulate cortex (ACC) process the “distress” component of both:
- Social rejection activates the ACC in the same way physical pain does (fMRI evidence)
- Low-dose opioids reduce social pain (e.g., Tylenol reduces hurt feelings in studies)
- This overlap likely evolved to make social bonds important for survival — social exclusion “hurts” in a literal neurobiological sense
Runner’s High — Endorphins and Endocannabinoids
The classic “runner’s high” explanation invokes endorphins, but the picture is more complex:
- Endorphins: released during sustained aerobic exercise; large peptides that cannot cross the blood-brain barrier — peripheral effects (pain tolerance, mild mood effects)
- Endocannabinoids (especially anandamide and 2-AG): small lipophilic molecules that do cross the BBB → central euphoria, anxiolysis, sedation
- Current evidence suggests endocannabinoids are the primary driver of exercise-induced euphoria; endorphins contribute to peripheral pain suppression and motivation
Opioid Addiction: Mimicking Endorphins
Exogenous opioids (morphine, heroin, fentanyl, oxycodone) bind the same μ-opioid receptors as β-endorphin, but with much higher potency and duration:
- Tolerance: Chronic activation → receptor downregulation → natural endorphins less effective → chronic low mood in absence of drug
- Withdrawal: Rebound hyperactivity of noradrenergic (locus coeruleus) and pain pathways when opioids removed
- Reward circuit hijacking: μ-opioid activation in the ventral tegmental area → dopamine release in nucleus accumbens → intense reinforcement (see Dopamin und Belohnung)
Understanding endogenous opioids is critical for understanding why opioid addiction is so powerful and why substitution therapies (methadone, buprenorphine) work by partial receptor engagement.
see also
Tags: HormoneNeurotransmitter science ai-generated
Superlink: 052 🫧Hormone und Neurotransmitter
Source
→ Einordnung: Neurotransmitter vs Neuropeptide vs Hormone · Hormone – Overview · Neuropeptide · CRH · Pain Perception
Erstellt: 01-09-22 11:15