Age-Dependent Changes in the Mechanisms Controlling Prolactin Secretion and Phosphatidylinositol Turnover in Male Rats: Effect of Phosphatidylserine

Abstract

The present study was undertaken in order to better characterize the functional state of anterior pituitary gland in young and old rats by using prolactin secretion and incorporation of radioactive phosphate into phosphatidylinositol (PI) as markers. The in vitro incorporation of radiolabeled phosphate into anterior pituitary PI was significantly (p< 0.01) greater in young (3–5 months) than in aged (24–25 months) male Sprague-Dawley rats. No significant difference was found in the incorporation by pituitary tissue of ³²P into phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Also, the extent of prolactin secretion from isolated pituitary was significantly greater in young than in aged rats, while the prolactin pituitary content was significantly higher in aged animals. In vitro dopamine (DA) decreased the incorporation of ³²P into PI, both in young and old pituitary glands, and inhibited prolactin secretion into the incubation medium. Brain cortex-phosphatidylserine (BC-PS), a pharmacologically active purified phospholipid, capable of stimulating the dopaminergic system in the hypothalamus and of decreasing prolactin secretion both in humans and rats in vitro and in vivo, inhibited the incorporation of labeled phosphate into PI of pituitary glands from either young or old rats, but did not alter the prolactin secretion from the glands incubated in vitro. Baseline prolactin plasma levels did not differ significantly between young and old rats either when blood was collected from the trunk after decapitation or underwent sampling from chronically cannulated rats. Chronic administration of BC-PS (15 mg/kg i.p. for 30 days) had a similar effect on prolactin plasma levels both in aged and young rats, while the phosphate incorporation into PI was significantly decreased only in young rats’ pituitaries. All together these data support the view that unchanged prolactin levels observed in old rats is the results of some adaptive compensatory mechanisms involved in the control of prolactin secretion.

Sexually Dimorphic Effects of Aging on Rat Somatotropes and Lactotropes

“…Consequently, all PRL measurements greatly increased in our old female rats. This finding corresponds to the higher PRL content previously reported (Cocchi et al, 1986;Bonetti et al, 1987).…”

Microinfusion of clonidine and yohimbine into locus coeruleus alters EEG power spectrum: effects of aging and reversal by phosphatidylserine

“…A reduction of prolactin secretion in rat lactotrophs during aging was also obtained after chronic treatment with PS (Toffano & Bruni, 1980;Zauli et al, 1984;Toffano, 1985). The changes in lactotrophs membrane fluidity during aging has been shown to affect phosphatidylinositol (PI) metabolism; PS was found to reduce in vitro 32P incorporation into PI and such an effect was associated with the inhibition of prolactin secretion (Bonetti et al, 1987).…”

Phosphatidylserine Containing Omega-3 Fatty Acids May Improve Memory Abilities in Nondemented Elderly Individuals with Memory Complaints: Results from an Open-Label Extension Study

“…In previous studies, administration of 200-300 mg/day of PS containing omega-3 fatty acids was found to have beneficial effects, purely symptomatic or neuroprotective [9,15,16,17,18,19]ones, on various types of cognitive impairment, ranging from age-associated cognitive decline to Alzheimer's disease [7,8,20,21,22,23,24]. …”