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Phasic firing enhances vasopressin release from the rat neurohypophysis
Author(s) -
Dutton A.,
Dyball R. E. J.
Publication year - 1979
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1979.sp012781
Subject(s) - vasopressin , pulse (music) , supraoptic nucleus , radioimmunoassay , stimulation , endocrinology , medicine , chemistry , in vivo , neuropeptide , tetrodotoxin , incubation , biology , biochemistry , physics , receptor , microbiology and biotechnology , detector , optics
1. Isolated rat neural lobes were incubated in vitro and electrically stimulated to release vasopressin. The released vasopressin was assayed using a radioimmunoassay and there was a reasonably good correlation ( r = 0.81) between results obtained with this assay and those obtained by bioassay with the rat blood pressure method. 2. Regular stimulation at frequencies of 5, 10 and 20 Hz released progressively more vasopressin and the release could be blocked by addition of tetrodotoxin to the incubation medium. 3. Stimulation with pulse patterns derived from tape recordings of phasically firing units in the supraoptic nucleus of dehydrated rats released more vasopressin than the same number of pulses regularly spaced in time. In the range 2‐8 pulses/sec vasopressin release was related to the pulse frequency within the bursts ( r = 0.90) and the number of short (< 100 msec) interpulse intervals ( r = 0.92). Vasopressin released per pulse increased over the frequency range 3‐6 pulses/sec, but above 6 pulses/sec vasopressin release per pulse tended to diminish. 4. We conclude that phasic firing of vasopressin neurosecretory cells may enhance vasopressin release in vivo and that an important factor in determining release is the number of short interspike intervals.