抄録
The temporal resolution for measuring of vasopressin (VP) release from neurohypophysial nerve terminals is relatively poor. We describe a fibre optic approach for monitoring VP release from the neurohypophysis in response to physiological stimuli, in vivo. Transgenic rats expressing a VP-enhanced green fluorescent protein (eGFP) fusion gene (Ueta et al., 2005, Endocrinology, 146: 406-413) were used. A dual optrode consisting of two optic fibres was constructed; one fibre coupled to a 488nm Ar laser was used for excitation and the other was used for signal detection. The optrode was stereotaxically placed immediately dorsal to the neurohypophysis during bolus intravenous injections of hypertonic saline (HS; 0.1ml, 3M NaCl) and sodium nitroprusside infusion (SNP; 100μM; 100μl/min for 5 min) to unload baroreceptors. HS-induced a rapid increase in fluorescence (40.2±3.2%; n=5, P<0.05) signal lasting approximately 40 s while infusion of SNP, to induce a sustained fall in arterial pressure, was associated with a stimulus-locked increase in fluorescence (19.5±1.5%; n=3). Neither bolus injections nor infusions of saline (0.9%) caused a change in fluorescence. Post-hoc histological analysis confirmed a change in fluorescent signal was detected to HS (n=5) and SNP (n=3) only when the optrode was positioned above the neurohypophysis. We concluded that optrode recording permits detection of putative VP release from the neurohypophysis in vivo. [J Physiol Sci. 2008;58 Suppl:S138]
