Medina V M, Gupta D, Gintzler A R
Department of Biochemistry, State University of New York Health Science Center at Brooklyn 11203, USA.
J Neurochem. 1995 Sep;65(3):1374-80. doi: 10.1046/j.1471-4159.1995.65031374.x.
This laboratory has previously reported that the maternal opioid analgesia associated with pregnancy and parturition is mediated, at least in part, by a maternal spinal cord dynorphin/kappa opioid system. This analgesia is accompanied by an increase in dynorphin peptides (1-17 and 1-8) in the lumbar spinal cord. Levels of trypsin-generated arginine6-leucine-enkephalin (Leu-Enk-Arg)-immunoreactive determinants were also determined and used to reflect the content of dynorphin precursor intermediates. In spinal tissue, the amount of dynorphin A (1-17) contained in the form of precursor is, at a minimum, 10-fold higher than the content of mature dynorphin A (1-17) or dynorphin (1-8). During gestational day 22, the content of dynorphin precursor is reduced significantly (approximately 50%). The decline in the magnitude of dynorphin precursor intermediates in the spinal cord of pregnant rats vastly exceeds the magnitude of increase in the content of dynorphin peptides (1-17 and 1-8). This difference can best be explained by postulating a corresponding increase in the rate of release of spinal cord dynorphin (1-17). It is suggested that enhanced processing of dynorphin precursor intermediates represents the initial biochemical level of adaptation of spinal dynorphin neurons to increased demands of pregnancy.
