Activity of oxytocinergic neurons in the supraoptic nucleus under stimulation of alpha2-adrenoceptors in Brattleboro rats.
Vasopressin (AVP) deficient homozygous Brattleboro rats exhibit severe osmotic challenges due to waterless chronic hypernatremia and hyperosmolality. We investigated the effect of xylazine, an alpha2-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-mum 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 alpha2-adrenoceptor stimulation.
Bundzikova
Jana
J
Laboratory of Functional Neuromorphology, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Slovakia.
Pirnik
Zdeno
Z
Mikkelsen
Jens D
JD
Zelena
Dora
D
Kiss
Alexander
A
D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000818:Animals; D001127:Arginine Vasopressin / Q000172:deficiency; D004326:Drinking; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D010121:Oxytocin / Q000378:metabolism*; D017440:Photoperiod; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D011910:Rats, Brattleboro / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D013495:Supraoptic Nucleus / Q000166:cytology* / Q000378:metabolism
D000316:Adrenergic alpha-Agonists; D016760:Proto-Oncogene Proteins c-fos; D018341:Receptors, Adrenergic, alpha-2; D001127:Arginine Vasopressin; D010121:Oxytocin