Smooth endoplasmic reticular whorls in neurons of the arcuate nucleus in male rats following adrenalectomy

(1) Adrenalectomy in the white rat induces the formation of smooth endoplasmic reticular (SER) whorls in arcuate nucleus neurons comparable to those seen after castration, thyroidectomy, morphine treatment and during the diestrus-proestrus phase of the estrus cycle. (2) The formation of compound endoplasmic reticulum (CER) and tubuloreticular structures (TRS) were also observed after adrenalectomy. (3) The number of SER whorls observed in tanycyte-like processes in relation to the pial membrane of the median eminence and to the non-fenestrated capillaries of the inferior median eminence after adrenalectomy was increased 9–13 fold over that noted in controls. (4) SER whorls in arcuate neurons occur following castration, thyroidectomy, adrenalectomy, after morphine treatment and in relation to some phases of the estrous cycle. Therefore, it is suggested that whorl formation in these neurons represents a morphologic index of increased neuronal activity related in some manner to the increased synthesis or release of the appropriate hypothalamic regulatory hormones for FSH-LH, TSH, ACTH and STH, not simply LH as previously suggested.