1984 Volume 5 Issue 6 Pages 473-480
Pineal glands from albino rats, Syrian hamsters, Mongolian gerbils, normal random bred mice and Snell dwarf mice have been found to contain measurable levels of immunoreactive somatostatin (IRS). The Snell dwarf (79.24±19.18 ng IRS/mg protein) and normal mice (37.33±4.8 ng IRS/mg protein) exhibited the highest concentrations followed by hamsters (4.05±0.93 ng IRS/mg protein), gerbils (3.66±1.26 ng IRS/mg protein) and rats who had the lowest (2.9±0.56 ng IRS/mg protein). A circadian rhythm of IRS was found to exist in the albino rat pineal with a peak value at the end of the light period (14 h) and a nadir towards the end of the dark period (10 h). Neither continuous light for one week, nor bilateral superior cervical ganglionectomy was found to exert any effect content between male and female mice. Daily injections of 25 μg of melatonin or 5-methoxytryptamine (5-MT) for 8 weeks produced no significant changes in pineal IRS levels in male hamsters; however, IRS tended to be higher in the melatonin injected group (277.84±90.3 pg IRS/pineal) than in the control (159.68±53.54 pg IRS/pineal) and 5-MT-treated (91.21±24.98 pg IRS/pineal) animals. It is concluded that IRS is found in the pineal gland of 5 different rodent species and exhibits a circadian rhythm in rats.
