Salsolinol Up‐Regulates Oxytocin Expression and Release During Lactation in Sheep

Abstract

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) is a dopamine-derived compound present in the central nervous system and pituitary gland. Several previous studies on lactating sheep and rats have reported that salsolinol plays a crucial role in the regulation of prolactin secretion. The present study investigated the effects of salsolinol, which was infused into the third ventricle of the brain, on oxytocin expression and release in lactating sheep, 48 h after weaning of 8-week-old lambs. Serial 30-min infusions of salsolinol and vehicle were performed at 30-min intervals from 10.00 to 15.00 h. Blood samples were collected every 10 min. The supraoptic nucleus (SON), paraventricular nucleus (PVN) and posterior pituitary were collected immediately after the experiment. Expression levels of mRNAs for oxytocin and peptidylglycine α-amidating monooxygenase (PAM), the terminal enzyme in the oxytocin synthesis pathway, were measured using a real-time polymerase chain reaction. Oxytocin peptide content in the posterior pituitary was measured by an enzyme-linked immunosorbent assay, and plasma oxytocin concentration was measured by radioimmunoassay. Salsolinol treatment significantly up-regulated oxytocin and PAM gene expression in the SON (P < 0.01 and P < 0.05, respectively), PVN (P < 0.01 and P < 0.05, respectively) and posterior pituitary (P < 0.05 and P < 0.05, respectively). Oxytocin peptide content in the posterior pituitary and the area under the response curve of plasma oxytocin were significantly (P < 0.05 and P < 0.01, respectively) higher in salsolinol-treated sheep than in control animals. The present study shows for the first time that salsolinol stimulates oxytocin secretion during lactation in sheep.

Up-regulation of oxytocin receptor gene and protein in the sheep anterior pituitary by a dopamine derivative (salsolinol)

“…Moreover, the dopamine derivative salsolinol, which is a stimulatory agent for the release of both PRL ) and OT (Gorski et al 2016) in lactating sheep, also up-regulated the OTR contents in the AP, which were higher during lactation than during seasonal anestrus.…”

“…Salsolinol, when i.c.v. administered in lactating sheep, upregulated OT gene expression in the PVN and SON, increased OT peptide content in the posterior pituitary, and stimulated OT release into the peripheral circulation (Gorski et al 2016).…”

Neurotoxicity and Underlying Mechanisms of Endogenous Neurotoxins

“…Sal contributes to alcohol addiction [ 41 ] and the production of neuroendocrine system-related hormones (e.g., prolactin [ 42 ], oxytocin [ 43 ]). Sal can be obtained from exogenous substances such as bananas, cheese, and alcoholic beverages.…”

Adaptive Modifications of Maternal Hypothalamic-Pituitary-Adrenal Axis Activity during Lactation and Salsolinol as a New Player in this Phenomenon

“…In lactating sheep, suckling induced an increase in the extracellular concentration of salsolinol within the IN/ME, which was closely related to the changes in plasma concentration of prolactin [ 102 ]. Moreover, salsolinol effectively stimulated both prolactin and oxytocin secretion in lactating sheep, when infused into the IIIv [ 84 , 112 ]. Furthermore, intracerebroventricular infusions of 1-MeDIQ, a compound antagonizing the salsolinol actions, attenuated both prolactin [ 111 ] and oxytocin [ 113 ] surge evoked by the suckling stimulus, suggesting that salsolinol might mediate suckling-induced release of both hormones.…”