The vasopressin positive elements in the hypothalamic magnocellular nuclei of rats treated with histamine

The vasopressin (AVP) positive elements of the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei, were investigated in 180 male rats through immunohistochemical, morphometric and statistical methods. The rats were subdivided in the next groups: 20 control rats; 40 rats treated with physiological saline intraperitoneal via (ip); 40 rats treated with physiological saline intracerebroventricular via (icv); 40 histamine (HA) treated rats, ip; and 40 HA treated rats, icv. The labeled nerve cells appear in the lateral part of the PNV and the SON of the control animals. These neurons have central nucleus and vasopressin positive cytoplasmic granulations. After the treatment with physiological saline, ip or icv, no alterations were observed. In HA treated rats, icv, numerous neurons strongly labeled were observed in these hypothalamic nuclei. Vasopressin positive nerve fibers and large droplets were also found both in the SON and in the PVN of these animals. The vasopressin positive material in the control rats and in HA treated rats, ip, is similar. The morphometric and statistical studies confirm these findings. The results are discussed in this paper.