Changes induced by formalin in the hypothalamic neurosecretory system of the spotted owlet, athene hrama temminck

Abstract

Histological changes induced in the HNS of the spotted owlet, Athene hrama Temminck. by injection of 1 ml 5 or 10% formalin arc described. No difference could be detected in the response of the HNS to 5 or 10% formalin administration. In the HNS of birds killed within 5 tnin of formalin administration, there was only partial depletion of NSM from the neurons, the tract and the NL: The quantity of NSM in the AME remained more or less unchanged. In animals killed 10-90 min after formalin injection, the depletion of NSM from the neurons, the tract and the NI, was more complete. The neurons of the preoptic division of the SON exhibited the maximum response: These neurons were also moderately hypertrophied. The NL also was hypertrophied in some animals; the NSM in the AME registered only a partial loss. The interval between formalin administration and killing did not influence the degree of changes in the HNS. The depletion of NSM was no greater at 90 min following formalin injection than at 10 min. Since it is well established that formalin stress causes augmented secretion of ADII and that there is a close functional relationship existing between ADH and NSM. the depletion of NSM noticed in the HNS of the spotted owlet following formalin administration is interpreted as indicating augmented secretion of ADH. Hence it seems that the responses of the HNS of birds to formalin stress are comparable to those of the 1INS of mammals. The results thus provide histological evidence in favour of the concept that stressful stimuli cause increased secretion of ADH. © 1975 S. Karger AG, Basel.