The Reproductive Decline in Male Rats

Steger, Richard W.; Huang, Henry D.

doi:10.1007/978-1-4684-4523-7_8

Cited by 5 publications

(1 citation statement)

References 42 publications

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“…Hyperprolactinemia is observed in aging female rats at all stages from middle age to the ultimate anestrous state, and an increased incidence of pituitary tumors, mostly prolactin-secreting tumors, has been documented in old rats [2][3][4], Concomitantly, the cyclic secretion of gonadotrophins is impaired [1,5,6] and both the alterations in prolactin and gonadotrophin secretions are suggestive that hypothalamic impairments contribute to the age-related neuroendocrine changes in reproductive function. In the male rat, aging is also char acterized by hyperprolactinemia associated with de creased secretions of gonadotrophins and testosterone [7,8], Studies of the mechanisms underlying the hypersecre tion of prolactin with aging have disclosed a marked and sustained reduction in the secretory activity of the hypo thalamic tuberoinfundibular dopaminergic (TIDA) neu rons in old (22-26 months) compared to young (3-5 months) rats, based on data obtained in vivo [9][10][11][12][13] and in vitro [14,15]. The reduced concentration of dopa mine observed in the mediobasal hypothalamus and median eminence of old rats ( fig.…”

Section: Aging and Reproductive Functionmentioning

confidence: 99%

Neuroendocrine Aspects of Aging: Experimental Data

Reymond¹,

Donda²,

Lemarchand-Béraud³

1989

Horm Res

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Aging is characterized by changes in neuroendocrine/endocrine functions which are manifest in female reproductive physiology and less perceptible in other functions such as thyroid, adrenal or growth/metabolic functions. The contribution of each level of the axis – hypothalamus, adenohypophysis or peripheral tissues – is not clearly established. Functional impairments with age are recognized in the peripheral glands (gonad, thyroid, adrenal) as well as in the pituitary, but increasing evidence is accumulating for a marked contribution of the hypothalamus in the age-associated endocrine changes observed in animals and humans. In old rats, multineuronal dysfunctions are demonstrated in the hypothalamus, with a documented decline in the activity of the neurons producing dopamine and thyrotropin-releasing hormone, and to a lesser extent luteinizing hormone- and growth hormone-releasing hormones, and alterations in regulatory mechanisms of these neurons are disclosed. Moreover, impairments are observed in the processing – binding, accumulation and intracellular distribution – of hypothalamic hormones in the adenohypophysis of old rats. Taken together, these observations are supportive of the view that the neuroendocrine/endocrine changes appearing with age result from a complex balance of functional alterations occurring at each level – central and peripheral – of the axis.

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Section: Aging and Reproductive Functionmentioning

confidence: 99%

Neuroendocrine Aspects of Aging: Experimental Data

Reymond¹,

Donda²,

Lemarchand-Béraud³

1989

Horm Res

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Age-related alterations in the stimulated release in vitro of catecholamines and luteinizing hormone-releasing hormone from the male rat hypothalamus

et al. 1987

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Using an in vitro perifusion system, the present study investigated the possibility that alterations in catecholamine and luteinizing hormone-releasing hormone (LHRH) secretion from the male rat mediobasal hypothalamus are present during the period of middle-age. The results indicate that, while tissue concentrations and baseline secretion of norepinephrine, dopamine and LHRH were similar between age groups, the patterns of dopamine and LHRH release in response to a series of depolarizing stimuli was different in the older animals. After all challenges, dopamine concentrations in the perifusate declined much more sharply for the middle-aged group, a finding that may be associated with a decrease with age in the pool of transmitter available for ready release. Also, tissue fragments from young adult rats were able to maintain the release of LHRH to a greater extent than tissue from the middle-aged animals, but only for the initial challenge period. The typical episodic pattern of LHRH release appeared to be disrupted in the older group following a second stimulus. It is possible that these age-related changes are early components of a disruption in the hypothalamic mechanisms governing gonadotropin secretion.

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