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Activity of Oxytocinergic Neurons in the Supraoptic Nucleus under Stimulation of α2‐Adrenoceptors in Brattleboro Rats
Author(s) -
Bundzikova Jana,
Pirnik Zdeno,
Mikkelsen Jens D.,
Zelena Dora,
Kiss Alexander
Publication year - 2008
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1410.016
Subject(s) - supraoptic nucleus , endocrinology , medicine , vasopressin , xylazine , stimulation , hypernatremia , chemistry , fixative , paraformaldehyde , saline , hypothalamus , oxytocin , chloral hydrate , pentobarbital , nucleus , biology , sodium , anesthesia , ketamine , neuroscience , biochemistry , organic chemistry , cytoplasm
Vasopressin (AVP) deficient homozygous Brattleboro rats exhibit severe osmotic challenges due to waterless chronic hypernatremia and hyperosmolality. We investigated the effect of xylazine, an α2‐adrenoceptor agonist, on the activity of oxytocinergic (OXY) neurons in the supraoptic nucleus (SON) of homozygous (di/di), heterozygous (di/+), and control (+/+) rats. Ninety minutes after saline (0.1 mL/100 g b.w., i.p.) or xylazine injection (10 mg/kg, i.p.) rats were anaesthetized with pentobarbital (50 mg/kg i.p.) and sacrificed by transcardial perfusion with fixative. Activity of OXY neurons was evidenced by nuclear Fos protein immunoreactivity. Fos/OXY colabelings were analyzed on 40‐μm thick coronal sections using computerized light microscope. As expected, plasma osmolality and water intake revealed high heterogenity within the di/di group of rats. Fos expression in SON of di/di rats was correlated with osmolality of each rat. In saline‐treated rats, maximum activation of Fos reached around 4% in +/+, 20% in di/+ rats, and as much as 60% in di/di rats. Xylazine activated in SON about 70% of OXY‐ergic neurons in +/+, 60% in di/+ rats, and more than 80% in di/di rats. The present findings indicate that in spite of the high spontaneous activity of SON OXY‐ergic neurons due to the AVP deficiency in di/di rats, many of the silent OXY‐ergic neurons in the SON remained acceptable for α2‐adrenoceptor stimulation.