Adrenalectomy potentiates noradrenergic suppression of GABAergic transmission in parvocellular neurosecretory neurons of hypothalamic paraventricular nucleus.
Glucocorticoids are known to regulate both the noradrenergic and GABAergic inputs to the paraventricular nucleus (PVN). However, little is known about the effects of glucocorticoids on the interaction of these two input systems. Here we examined the effects of bilateral adrenalectomy (ADX) on the noradrenergic modulation of GABAergic transmission in the type II PVN neurons labeled with a retrograde dye injected into the pituitary stalk. Noradrenaline either reduced or augmented the frequency of spontaneous inhibitory postsynaptic current (sIPSC) without changing the amplitude and decay time constant. These effects were blocked by alpha2A- and alpha(1A/1L)-adrenoceptor antagonists, respectively. ADX increased the proportion of the neurons showing the noradrenergic reduction and the extent of reduction in the IPSC frequency. The ADX-induced changes were reversed by supplementation of ADX rats with corticosterone (10-mg pellet). ADX also potentiated the noradrenergic reduction in the frequency of miniature IPSC and paired-pulse facilitation of evoked IPSC. BRL 44408 (3 microM), a alpha2A-adrenoceptor antagonist, blocked the noradrenergic reduction in ADX rats. Corticotropin-releasing hormone and/or vasopressin transcripts were detected in neurons displaying noradrenergic augmentation or reduction of IPSC frequency. ADX enhanced the proportion of neurons expressing corticotropin-releasing hormone. Collectively, the results suggest that depletion of corticosterone by ADX markedly potentiates the noradrenergic suppression of GABAergic transmission mediated by the alpha2A-adrenoceptors on the GABAergic terminals in the parvocellular neurosecretory PVN neurons. These results may provide a novel synaptic mechanism for the glucocorticoid-induced plasticity in the noradrenergic modulation of neuroendocrine function of the PVN.
Yang
Jian Hua
JH
Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul, Republic of Korea.
Li
Long Hua
LH
Shin
Seung Yub
SY
Lee
Sora
S
Lee
So Yeong
SY
Han
Seong Kyu
SK
Ryu
Pan Dong
PD
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000315:Adrenalectomy / Q000379:methods; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002232:Carbocyanines / Q000378:metabolism; D003345:Corticosterone / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects* / Q000502:physiology; D054833:Isoindoles / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009638:Norepinephrine / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014667:Vasopressins / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
C035005:3,3'-dihexadecylindocarbocyanine; D000317:Adrenergic alpha-Antagonists; D002232:Carbocyanines; D018691:Excitatory Amino Acid Antagonists; D007093:Imidazoles; D054833:Isoindoles; D014667:Vasopressins; D005680:gamma-Aminobutyric Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone; D009638:Norepinephrine; C072125:BRL 44408