Changes in the kinetics of ( sup 3 H)dopamine release from median eminence and striatal synaptosomes during aging

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Endocrinology; (USA)

DOI:https://doi.org/10.1210/endo-126-1-228· OSTI ID:6984015

Gregerson, K A; Selmanoff, M ^[1]

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1. Univ. of Maryland School of Medicine, Baltimore (USA)

The release of preaccumulated tritium-labeled dopamine was examined in isolated nerve terminals prepared from the median eminence (ME) and corpus striatum (CS) of young, middle-aged, and old male rats. Fractional release of (3H)DA was measured over 1- to 10-sec time intervals under basal and depolarizing conditions in the presence of calcium. No differences in the rate of basal efflux between the age groups were observed in either ME or CS preparations. Fast-phase evoked (3H)DA release from CS synaptosomes was unchanged from young to middle-aged, but was decreased in old preparations. These data demonstrate that the nigrostriatal nerve terminal has a diminished ability to respond fully to depolarizing stimuli in advanced age. Mean serum PRL levels in old rats were 2.3-fold greater than those in both young and middle-aged rats, while serum LH levels were decreased 2.0-fold in middle-aged and old compared with those in young rats. The fact that LH levels were already decreased in middle-aged rats while PRL levels had not yet increased suggests that decreased gonadotropin titers in old rats do not result from the coincident hyperprolactinemia. In ME synaptosomes, depolarization-induced (3H)DA release was decreased at all time points in middle-aged preparations compared to that in young preparations. The reduced fractional release from the middle-aged ME synaptosomes was due to a depressed rate of release during the initial second of depolarization. Evoked release from ME terminals of old rats was comparable to that measured in the young group. Thus, there occurred an age-related biphasic change in the initial rate of evoked DA release from ME synaptosomes. Diminished response of ME dopaminergic terminals to depolarizing stimuli during middle age may be important in the later development of hyperprolactinemia in aging male rats.

• OSTI ID: 6984015
• Journal Information: Endocrinology; (USA), Vol. 126:1; ISSN 0013-7227
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
DOPAMINE
SECRETION
LH
BIOSYNTHESIS
AGE DEPENDENCE
BIOCHEMICAL REACTION KINETICS
HOMEOSTASIS
NERVE CELLS
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
AMINES
ANIMAL CELLS
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
CARDIOTONICS
CARDIOVASCULAR AGENTS
DRUGS
GONADOTROPINS
HORMONES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
NEUROREGULATORS
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PHENOLS
PITUITARY HORMONES
POLYPHENOLS
REACTION KINETICS
RODENTS
SOMATIC CELLS
SYMPATHOMIMETICS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques