Vasopressin-Enhanced Green Fluorescent Protein and Oxytocin-Monomeric Red Fluorescent Protein 1 in Colchicine Treated Transgenic Rats

Abstract

Arginine vasopressin (AVP) and oxytocin (OXT) are synthesized in the magnocellular neurosecretory cells (MNCs) of the hypothalamic paraventricular (PVN) and supraoptic nuclei (SON) that terminate their axons in the posterior pituitary (PP). Recently, we generated transgenic rats that express AVP-enhanced green fluorescent protein (eGFP) fusion gene and OXT-monomeric red fluorescent protein 1 (mRFP1) fusion gene in order to visualize AVP or OXT in the hypothalamo-neurohypophysial system (HNS). Colchicine is known to block axonal transport, resulting in peptide accumulation in the cell body. We investigated the effects of intracerebroventricular (icv) administration of colchicine on the expression of AVP-eGFP fusion or OXT-mRFP1 fusion gene products. Icv administration of colchicine caused a marked increase of AVP-eGFP and OXT-mRFP1 fluorescence in the hypothalamic MNCs, and a decrease in the PP in comparison with control rats. The expected changes of AVPeGFP and OXT-mRFP1 fluorescence in the HNS after icv administration of colchicine indicate that AVP-eGFP and OXT-mRFP1 fusion protein may be transported by axonal flow and secreted from the PP into the systemic circulation. These transgenic rats are new tools to study the physiological role of AVP and OXT in the HNS.