Abstract:In a young adult (8 weeks old) Sprague-Dawley (SD) rat, a 7 mm-diameter hemispherical nodule with white spots was macroscopically identified on the visceral surface of the spleen. Microscopically, the nodule consisted of areas of enlarged white pulp. The periarteriolar lymphoid sheaths (PALS) area was expanded due to an increase in lymphocytes, but the marginal zone was relatively atrophied. Although minimal compressions and mitotic figures were sporadically observed, there were no structural alterations or atypical cells. Immunohistochemically, there were increased numbers of proliferating cells (Ki-67 positive cells) in the PALS and red pulp areas. In the PALS area, there were increased numbers of T-cells and macrophage/dendritic cells, while in the red pulp area, there were increased numbers of T-cells and B-cell/plasma cells. This lesion, which is believed to be hyperplastic and not neoplastic, was diagnosed as lymphoid hyperplasia, a condition considered to be uncommon in young adult SD rats. (J Toxicol Pathol 2008; 21: 243-247)

Haloperidol, a neuroleptic, was orally given to Sprague-Dawley rats for 2 or 4 weeks, starting at 8 and 6 weeks of age. The dose levels were 0, 30 and 60 mg/kg/day for the 4-week treatment groups, and 0, 30, 60 and 80 mg/kg/day for the 2-week treatment groups. On the day after the last administration, rats were anesthetized and sacrificed at 10 weeks of age. The absolute weights of the testes and epididymides were decreased after 2- and 4-weeks at 30 mg/kg/day or above. The absolute and relative weights of the prostate and seminal vesicles were also decreased after 2-weeks at 60 mg/kg/day or above, and 4-weeks at 30 mg/kg/day or above. The histopathological alterations observed after 2-weeks at 30 mg/kg/day were as follows: atrophy of Leydig cells, numerous necrotic pachytene spermatocytes in seminiferous tubules of stage VII, retention of mature spermatids, exfoliation of round spermatids in lumina of seminiferous tubules, cell debris in lumina of the epididymis. At 60 mg/kg/day or above, these alterations were pronounced. Histopathological changes were comparable to those detected after 4-weeks treatment. It was concluded that alterations of the male reproductive organs are detectable by a 2-week administration of haloperidol in rats to almost the same degree as after 4-weeks treatment.

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