Prenatal caffeine exposure induces down-regulation of the protein kinase A/ryanodine receptor/large-conductance Ca2+-activated K+ pathway in the cerebral arteries of old offspring rats

Abstract

Background/aims: The current study investigated the long-term effects of prenatal caffeine (Caf) exposure on cerebral vessels of old offspring rats. Methods: Pregnant rats were treated with Caf (20 mg/kg, twice daily) or 0.9% normal saline during gestational days 3.5–19.5, and offspring were tested at 24 months old. Vascular functions of middle cerebral arteries and ion channel activities in smooth muscle cells were examined using myograph system and patch-clamp. Results: Prenatal Caf exposure decreased isoprenaline (β-adrenergic agonist)-induced dilatation of the middle cerebral artery in the offspring. Treatment with protein kinase A (PKA) inhibitor reduced isoprenaline-mediated vasodilatation to a greater extent in the control. Forskolin-mediated vasodilatation and membrane hyperpolarization were reduced in the Caf group. Large-conductance Ca2+-activated K+ (BKCa) channel inhibitor iberiotoxin significantly attenuated forskolin-induced vasodilatation and reduced depolarization in the control, not in the Caf group. The PKA agonist-activated cell-attached single BKCa currents to a greater extent in the control. The mRNA and protein expression levels of PKA-Cα were decreased. The sensitivity of ryanodine receptors to the PKA agonist was blunted in the Caf group, whereas the mRNA expression of ryanodine receptor 2 subunit was reduced. Voltage/Ca2+ sensitivity of BKCa was decreased accompanied by reduced mRNA and protein expression of BKCa-β1 subunits in the Caf group. PKA agonist-stimulated inside-out BKCa currents were weaker in the Caf group. Conclusion: Prenatal exposure to Caf-affected isoprenaline/forskolin-mediated vascular functions in aged cerebral arteries, related to dysfunction of the PKA/ryanodine receptors/BKCa signaling pathway.