Retinal and Pineal Hydroxyindole—O—Methyl Transferases in the Rat: Changes Following Cervical Sympathectomy, Pinealectomv or Blinding

Abstract

Retinal and pineal hydroxyindole— O—methyl transferases (HIOMT) exhibit 24–hr fluctuations with maxima during the light and dark period of the day, respectively. The effects of superior cervical ganglionectomy, pinealectomy or blinding on both enzymatic activities were investigated in male rats subjected to: a) ganglionectomy; b) pinealectomy; c) blinding; d) pinealectomy plus ganglionectomy; e) blinding plus ganglionectomy. Groups of rats were sacrificed every 4–8 hr during 2 days, and the HIOMT activity was determined in retinal and pineal homogenates. Ganglionectomy decreased retinal HIOMT activity, whereas pinealectomy increased it. Pinealectomy, or pinealectomy plus ganglionectomy, abolished the diurnal fluctuations in retinal HIOMT observed in intact or ganglionectomized rats. Blinding enhanced pineal HIOMT activity whereas ganglionectomy decreased it. Ganglionectomy, alone or combined with blinding, caused time—shifts in daily pineal HIOMT maxima. Norepinephrine (100–5OO μg ip) reversed the ganglionectomy— induced decreases in retinal and pineal HIOMT activities, but did not exhibit significant effects in intact rats. (Endocrinology92: 1560, 1973)