title: The Reproductive Cycle of Male Uinta Ground Squirrels and Its Relationship to Pineal N-Acetyltransferase and Monoamine Oxidase in the Testes, Hypothalamus and Pituitary
Creators: name: Palmer, Robert Alexander
Publisher: name: Utah State University
Year: 1975

description: A study was made of the reproductive cycle of male Uinta ground squirrels (Spermophilus armatus) during the activity seasons of 1973 and 1974 and during the aestivation/hibernation (A/H) period of 1973-1974. Physiological data collected were compared to changes in monoamine oxidase (MAO) activity of the testes, pituitary and hypothalamus and to pineal N-acetyltransferase activity.
Male Uinta ground squirrels began emerging from their burrows on April 12, 1973, and April 8, 1974, with average body weights of 302 g and 301 g, respectively. Body weight did not increase greatly during breeding, but rose rapidly to over a 500 g average prior to immergence into A/H. Body weight declined during A/H. Adrenal weight decreased in July, just prior to immergence into A/H and during A/H. An increase in adrenal weight occurred just prior to emergence from the burrows that was associated with and thought to be partially responsible for the marked gonadal and reproductive development at this time.
Testicular development (as shown by testicular weight, length, width and seminiferous tubule diameter) was similar to data reported for this and other species of ground squirrels. Maximum gonadal development was observed at emergence that was followed by a regression to a basal state in June. A slight testicular recrudescence occurred during the preA/H period in July and during the A/H period, but maximum growth occurred during the period of proposed arousal in mid-March to the actual emergence time. Testicular histology of the germinal epithelium and interstitial cells followed a similar pattern of development except that the interstitial cells and accessory organs did not develop until just prior to emergence of the animals from their burrows.
Plasma testosterone levels and seminal vesicle weights were both highest at emergence and both decreased concomitant with testicular regression. There was no significant increase in either parameter during the preA/H testicular recrudescence.
Data presented here corroborated the hypothesis that FSH stimulates testicular MAO activity. First, total MAO activity changes were highly correlated (r = 0.96) with changes in testicular development that are most certainly under partial control of pituitary gonadotropins. Second, the proliferation of spermatogonia during preA/H and A/H periods, but the lack of development beyond the spermatogonia stage suggests FSH stimulation, but no effective LR or testosterone stimulation. Third, the lack of interstitial cell development during preA/H and A/H suggests no effective LH stimulation. Fourth, the lack of an increase in plasma testosterone levels and seminal vesicle weights during preA/H and A/H periods also suggest no effective LH stimulation on the interstitial cell function. This increase in MAO activity with testicular development could protect the gonad from the deleterious effects of endogenous serotonin.
Pituitary and hypothalamic MAO followed the expected gonadotropin secretion pattern for testicular development found in the Uinta ground squirrel. These data suggest a functional role for MAO in controlling releasing factor and gonadotropin secretion by the hypothalamus and pituitary.
Diurnal variations in pineal N-acetyltransferase activity approached significance (p < 0.07) with 10:00 p.m. values greater than 10:00 a.m. values. A significant drop in pineal N-acetyltransferase activity in March just before arousal-emergence may facilitate testicular development at this time. High values at emergence may contribute to the rapid testicular regression immediately following emergence.