Activity of oxytocinergic neurons in the supraoptic nucleus under stimulation of alpha2-adrenoceptors in Brattleboro rats.

Abstract

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.

• Authors: Jana Bundzikova, Zdeno Pirnik, Jens D Mikkelsen, Dora Zelena, Alexander Kiss
• Journal: Annals of the New York Academy of Sciences (Ann N Y Acad Sci) Vol. 1148 Pg. 154-60 (Dec 2008) ISSN: 1749-6632 [Electronic] United States
• PMID: 19120104 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adrenergic alpha-Agonists
• Proto-Oncogene Proteins c-fos
• Receptors, Adrenergic, alpha-2
• Arginine Vasopressin
• Oxytocin

Topics

• Adrenergic alpha-Agonists (metabolism)
• Animals
• Arginine Vasopressin (deficiency)
• Drinking
• Neurons (cytology, metabolism)
• Osmolar Concentration
• Oxytocin (metabolism)
• Photoperiod
• Proto-Oncogene Proteins c-fos (metabolism)
• Rats
• Rats, Brattleboro (metabolism)
• Receptors, Adrenergic, alpha-2 (metabolism)
• Supraoptic Nucleus (cytology, metabolism)