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Potent inhibitory effect of selective D2and D3agonists on dopamine-responsive dorsomedial arcuate neurons in brain slices of estrogen-primed rats

Authors
Journal
Life Sciences
0024-3205
Publisher
Elsevier
Publication Date
Volume
69
Issue
22
Identifiers
DOI: 10.1016/s0024-3205(01)01342-x
Keywords
  • Dopamine Autoreceptor
  • Arcuate Nucleus
  • Single-Unit Recording

Abstract

Abstract The possible involvement of dopamine D 2 and D 3 receptors in the action of dopamine (DA) on inhibiting dorsomedial arcuate nucleus (dmARN) neurons in brain slices was determined in this study. Fresh brain slices were prepared from ovariectomized, estrogen-primed Sprague-Dawley rats and used for extracellular single-unit recording. The dmARN neurons were first identified by their inhibitory responses to DA and then tested with PHNO and/or PD128907, selective D 2 and D 3 agonists, respectively. PD128907 in 5–50 nmole doses significantly inhibited the majority of DA-responsive dmARN neurons (86.3% of 44 units). Moreover, PHNO in 5–25 nmole doses inhibited all DA-responsive neurons tested (100% of 34 units). The inhibitory effects of PHNO and PD128907 were not only prominent; but also persisted in low Ca 2+, high Mg 2+ medium, indicating that they were acting directly on the recorded neuron. Pretreatment of either raclopride or U99194A, D 2 and D 3 receptor antagonists respectively, reversed the effects of DA in a few trials. In contrast, SKF81297, a D 1 receptor agonist, induced variable responses in dmARN neurons. These results clearly indicate that DA may act through D 2 and/or D 3 receptors to exhibit an inhibitory effect on presumed TIDA neurons in dmARN.

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