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In Vivo Neurochemical Evaluation of Striatal Serotonergic Hyperinnervation in Rats Depleted of Dopamine at Infancy
Author(s) -
Jackson Denise,
Abercrombie Elizabeth D.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09340.x
Subject(s) - serotonergic , striatum , microdialysis , medicine , endocrinology , dopamine , neurochemical , serotonin , neurotransmitter , chemistry , basal ganglia , homovanillic acid , dorsal raphe nucleus , nigrostriatal pathway , dopaminergic , central nervous system , biology , substantia nigra , receptor
Destruction of nigrostriatal dopamine (DA) neurons with 6‐hydroxydopamine (6‐OHDA) early in development results in hyperinnervation of striatum by the serotonergic afferents deriving from the dorsal raphe nucleus. We have used in vivo microdialysis to investigate the degree to which serotonergic neurotransmission in striatum is altered by this increase in the density of serotonin (5‐HT) terminals. The effects of several manipulations known to influence 5‐HT function on extracellular 5‐HT and 5‐hydroxyindoleacetic acid in striatum were compared in adult rats treated neonatally with 6‐OHDA and in intact adult rats. Basal levels of 5‐HT in extracellular fluid (ECF) of striatum were similar in neonatally DA‐depleted rats and in intact rats. Perfusion with the 5‐HT reuptake blocker, fluoxetine (100 μM), increased 5‐HT in striatal ECF of neonatally DA‐depleted rats to levels that were threefold greater than those achieved in intact rats. Likewise, K+‐depolarization of the 5‐HT terminals (100 m M in perfusate) or systemic administration of the 5‐HT releaser, (±)‐fenfluramine (10 mg/kg i.p.), increased the concentration of 5‐HT in striatal ECF of neonatally DA‐depleted rats to levels approximately threefold greater than those observed in striatum of intact rats. These findings indicate that the 5‐HT hyperinnervation of striatum that takes place in rats depleted of DA at infancy is associated with an increased capacity for neurotransmitter release in this system. Concomitant increases in high‐affinity 5‐HT uptake may prevent the occurrence of any measurable changes in the resting concentration of 5‐HT in striatal ECF.