Dopamine and 7-OH-DPAT may act on D(3) receptors to inhibit tuberoinfundibular dopaminergic neurons.
Whether the tuberoinfundibular dopaminergic (TIDA) neurons resided in the dorsomedial arcuate nucleus (dmARN) can respond to dopamine and a dopamine D(3) receptor agonist, 7-hydroxydipropylaminotetralin (7-OH-DPAT), was the focus of this study. In studies using extracellular single-unit recording of dmARN neurons in brain slices obtained from ovariectomized rats, dopamine and 7-OH-DPAT inhibited 60.1% (n = 141) and 80.9% (n = 47) of recorded dmARN neurons, respectively. Other dopamine D(1) or D(2) receptor agonists were not as effective. Intracerebroventricular injection of 7-OH-DPAT (10(-9) mol/3 microl) in ovariectomized, estrogen-primed rats significantly lowered the TIDA neuronal activity as determined by 3, 4-dihydroxyphenylacetic acid (DOPAC) levels in the median eminence. Co-administration of a putative D(3) receptor antagonist, U-99194A, could prevent the effect of 7-OH-DPAT. Unilateral microinjection of 7-OH-DPAT or dopamine itself (10(-11)-10(-9) mol/0.2 microl) into the right dmARN exhibited the same inhibitory effect on TIDA neurons. In all, dopamine may act on D(3) receptors to exhibit an inhibitory effect on its own release from the TIDA neurons.
Lin
J Y
JY
Department of Physiology, School of Life Science, National Yang-Ming University, ROC, Taipei, Taiwan.
Yen
S H
SH
Shieh
K R
KR
Liang
S L
SL
Pan
J T
JT
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology*; D018491:Dopamine Agonists / Q000494:pharmacology*; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000378:metabolism; D050637:Receptors, Dopamine D3; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014371:Tuber Cinereum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D018491:Dopamine Agonists; C493595:Drd3 protein, rat; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D013764:Tetrahydronaphthalenes; C031349:7-hydroxy-2-N,N-dipropylaminotetralin; D004298:Dopamine