[ he concentrations of immunoreactive ( ir- ) peptides derived from the opioid peptide precursors proenkephalin a ( met-enkephalin ) , proenkephalin b [ dynorphin ( dyn ) - ( 1-17 ) , dynorphin- ( 1-8 ) , dynorphin b , alpha-neoendorphin ( alpha-neo-e ) , beta-neo-e ] and proopiomelanocortin [ beta-endorphin ( beta-end ) ] , and of the neurosecretory hormones vasopressin and oxytocin increased between approximately 10-fold and 50-fold from birth to adulthood in the rate hypothalamus .
C0205753
opioid
C0013355
dynorphin