Diminished prostaglandin-mediated inhibition of norepinephrine release from the sympathetic nerve endings in spontaneously hypertensive rats.

This study was performed to investigate prostaglandin (PG)-mediated regulation of norepinephrine release from the sympathetic nerve endings in spontaneously hypertensive rats (SHR). The effects of PGE2 on the pressor responses and norepinephrine overflow during the periarterial nerve stimulation were examined in the perfused mesenteric vascular beds from SHR and age-matched Wistar Kyoto rats (WKY). In preliminary studies using normotensive Wistar rats, PGE2 inhibited the overflow of norepinephrine in response to the electrical nerve stimulation. On the contrary, when indomethacin was infused into the preparations, the norepinephrine overflow induced by the nerve stimulation was increased. In SHR, the neurogenic vasoconstriction and norepinephrine overflow during the nerve stimulation were significantly greater than in WKY. PGE2 in the medium inhibited the pressor responses and norepinephrine overflow during the nerve stimulation dose-dependently in WKY, while the inhibitory effects of PGE2 in SHR were blunted. These results suggest that PGE2 is an important hormone in regulating sympathetic vascular tone and that presynaptic inhibition of vascular adrenergic transmission by PGE2 is attenuated in SHR.