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Is Vasopressin Preferentially Released from Corticotropin‐Releasing Factor and Vasopressin Containing Nerve Terminals in the Median Eminence of Adrenalectomized Rats?
Author(s) -
Goeij Dimphena C. E.,
Berkenbosch Frank,
Tilders Fred J. H.
Publication year - 1993
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1993.tb00369.x
Subject(s) - vasopressin , medicine , endocrinology , median eminence , immunocytochemistry , adrenalectomy , colchicine , radioimmunoassay , arginine , corticotropin releasing hormone , chemistry , hypothalamus , biology , biochemistry , amino acid
The effects of adrenalectomy (ADX) on the amounts of immunoreactive corticotropin‐releasing factor (CRF j ) and arginine vasopressin (AVP i ) that are stored in the zona externa of the median eminence (ZEME) were investigated by means of quantitative immunocytochemistry. Although ADX of male Wistar rats for 1 week or 4 weeks did not affect CRF i in the ZEME as compared to sham‐operated or intact controls, AVP i showed a progressive accumulation. The ratio of AVP i over CRF i in the ZEME had already increased 1 day after ADX. However, it should be noted that the exact changes in CRF i and AVP j as measured by radioimmunoassay and/or quantitative immunocytochemistry were dependent on the substrain of rats used. The secretion rate of CRF i and AVP j was estimated in 1 week and 4 week ADX rats, by measuring the disappearance rate of CRF i and AVP i from the ZEME after blockade of fast axonal transport, by a low non‐toxic dose of colchicine (5 μg per rat). In contrast to intact rats, where this dose of colchicine did not affect CRF i or AVP i in the ZEME, ADX rats showed a progressive depletion of the CRF i and AVP i stores as measured 2.5 and 5 h later. In 1 week ADX rats, CRF i and AVP i both disappeared at a rate of 7% to 8% of their stores per hour. In contrast, after 4 weeks of ADX the fractional disappearance rates of CRF i and AVP i were different and were 3% and 8% of the content per hour, respectively. This indicates that in long‐term ADX rats the chance of AVP being released from the ZEME is more than twice that of CRF. Since most, if not all, of the CRF; containing nerve terminals in the ZEME of ADX rats costore AVP, we hypothesize that in long‐term ADX rats AVP may be preferentially secreted from AVP and CRF costoring nerve terminals.