Effects of Hydrogen Sulfide in the Supraoptic Nucleus of the Hypothalamus on Gastric Motility in Rats

Hydrogen sulfide (H₂S), a gaseous neurotransmitter, plays critical roles in neuromodulation and autonomic regulation within the central nervous system (CNS). The supraoptic nucleus (SON), one of a number of hypothalamic regions governing neuroendocrine secretion, also projects to autonomic centers to modulate systemic functions. Despite evidence of H₂S activity in other brain regions, its specific role in the SON, particularly in regulating gastric motility, remains unexplored. Physiological saline (PS), L-cysteine (L-Cys, 2 nmol and 4 nmol), sodium hydrosulfide (NaHS, 2 nmol and 4 nmol), and combinations of NaHS with protein kinase A (PKA) inhibitor (H-89), p38 mitogen-activated protein kinase (p38-MAPK) inhibitor (SB203580), or adenylate cyclase-cyclic adenosine monophosphate (AC-cAMP) inhibitor (SQ22536) were microinjected into the SON of male adult Wistar rats (n = 5/group). Changes in gastric motility were detected and compared. The microinjection of either L-Cys or NaHS into the SON significantly inhibited gastric motility, with a greater inhibitory effect observed at the higher dose of each substance (p < 0.01). However, when H-89, SB203580, and SQ22536 were injected prior to the administration of NaHS, no significant changes in gastric motility were observed, thus indicating that these inhibitors completely counteracted the inhibitory effect of NaHS on gastric motility. The microinjection of endogenous or exogenous H₂S into the SON of rats inhibits gastric motility. This inhibitory effect may be mediated through the PKA, AC-cAMP, and p38-MAPK pathways.