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Dopamine D 1 Receptor Blockage Potentiates AMPA‐Stimulated Luteinising Hormone Release in the Goldfish
Author(s) -
Popesku J. T.,
Mennigen J. A.,
Chang J. P.,
Trudeau V. L.
Publication year - 2011
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.2011.02114.x
Subject(s) - medicine , endocrinology , ampa receptor , biology , agonist , glutamate receptor , hypothalamus , luteinizing hormone , kainate receptor , dopamine antagonist , dopamine , gonadotropin releasing hormone , hormone , receptor , haloperidol
Previous microarray analyses of the goldfish hypothalamus led us to hypothesise that dopamine could potentially inhibit the excitatory effects of glutamate on luteinising hormone (LH). Post‐spawning female goldfish were pre‐treated (−4.5 h) with either saline (C; control), SCH 23390 (S; D 1 ‐receptor antagonist) or sulpiride (L; D 2 ‐receptor antagonist), followed by an i.p. injection, at −0.5 h, of saline or the glutamate agonist AMPA (A, SA or LA). Blood, hypothalamus and telencephalon tissues were collected. Serum LH was not affected in the S, L, A, or LA groups relative to control as determined by radioimmunoassay. The SA group, however, showed a 289% (P < 0.0005) increase in serum LH compared to either treatment alone or control. Real‐time reverse transcriptase‐polymerase chain reaction identified the mRNAs for ionotropic (Gria2a, Gria4) glutamate receptor subunits, activin βa, isotocin, and cGnRH‐II as being significantly affected by some of the treatments. The same experiment conducted with sexually‐regressed female fish showed a very different LH profile, indicating that this mechanism is seasonally‐dependent. We also show that i.p. injection of 1 μg/g isotocin was able to increase LH levels by 167% in sexually regressed female fish relative to controls. Taken together, these results demonstrate that blockage of the D 1 receptor primes post‐spawning goldfish for AMPA‐stimulated LH release, and provides further insights into the central regulation of reproduction.