Effects of morphine and morphine withdrawal on brainstem neurons innervating hypothalamic nuclei that control the pituitary-adrenocortical axis in rats.
Different data support a role for brainstem noradrenergic inputs to the hypothalamic paraventricular nucleus (PVN) in the control of hypothalamus - pituitary - adrenocortical (HPA) axis. However, little is known regarding the functional adaptive changes of noradrenergic afferent innervating the PVN and supraoptic nucleus (SON) during chronic opioid exposure and upon morphine withdrawal. Here we have studied the expression of Fos after administration of morphine and during morphine withdrawal in the rat hypothalamic PVN and SON. Fos production was also studied in brainstem regions that innervate hypothalamic nuclei: the nucleus of solitary tract (NTS - A2) and the ventrolateral medulla (VLM - A1) and combined with immunostaining for tyrosine hydroxylase (TH) for immunohistochemical identification of active neurons during morphine withdrawal. Male rats were implanted with s.c. placebo or morphine (tolerant/dependent) pellets for 7 days. On day 8 rats received an injection of saline i.p., morphine i.p., saline s.c. or naloxone s.c. Acute morphine administration produced an increase in Fos expression at hypothalamic nuclei and in the brainstem regions, and tolerance developed towards this effect. Precipitated morphine withdrawal induced marked Fos immunoreactivity within the PVN and SON. Concomitantly, numerous neurons in the brainstem were stimulated by morphine withdrawal. Moreover, catecholaminergic-positive neurons in the brainstem showed a significant increase in Fos expression in response to morphine withdrawal. These findings demonstrate that chronic activation of opioid receptors results in altered patterns of immediate-early genes (IEG) expression in the PVN and SON, which occurs concurrently with an increased activity of their inputs from the brainstem.
Laorden
Maria Luisa
ML
Equip of Cellular and Molecular Pharmacology, University School of Medicine, 30100 Murcia, Spain.
Castells
Maria Teresa
MT
Milanés
Maria Victoria
MV
D000818:Animals; D001933:Brain Stem / Q000187:drug effects* / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D017781:Genes, Immediate-Early; D007030:Hypothalamo-Hypophyseal System; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D009021:Morphine Dependence / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D010913:Pituitary-Adrenal System; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D002395:Catecholamines; D009292:Narcotic Antagonists; D016760:Proto-Oncogene Proteins c-fos; D009270:Naloxone; D014446:Tyrosine 3-Monooxygenase