Harderian glands, first described by Jacob Harder in two species of deer in 1694, are large, intraorbital glands which, with but few exceptions, are found in all land vertebrates. Certainly, their relatively large size, their phylogenetic age, and persistent conservation in all groups as they emerged from an aqueous to an air/land environment lend strong support to the logical deduction that they probably play an important role in the physiological adaptation to terrestrial life. Yet, few biologists know even what or where these glands are. For a variety of reasons, the Harderian glands have not received the attention they deserve and, as a result, the published works available have been scarce and scattered throughout the world literature. The current situation is remarkably similar to that which existed in regard to the pineal gland prior to the mid-1960s, i. e. , scattered literature, unknown function, few investigators, and little interest. Yet, following a few key papers, interest in the pineal gland expanded and soon an explosive increase in the knowledge and understanding of the pineal gland took place and continues today. Will history repeat itself? Originally, a few of us discussed the desirability of an informal Symposium on the Harderian glands.
This volume contains the written contributions to the proceedings of a workshop related to the pineal gland and its hormones, which was held in Erice, Italy, on June 7 -June 13, 1994. This series of workshops, which began in 1982 and which have been held at four-year intervals since that time, has provided important continuity for advancing the state of knowledge relating to this very important investigative area. The enthusiasm for these conferences has increased steadily, as reflected in the number of individuals applying to attend and in the input of individuals who participate in the meeting. The 1994 meeting was important because of its timeliness. In the two years preceding the meeting a number of revolutionary discoveries were made relative to the actions of the pineal hormone melatonin. The Xenopus melatonin receptor was cloned, melatonin was demonstrated to be a potent antioxidant, the significance of melatonin receptors at the level of pars tuberalis in the regulation of the hypothalamo-pituitary-gonadal axis was questioned, a number of melatonin receptor analogues were discovered and successfully utilized, the mechanisms by which melatonin retards initiation and promotion of cancer was further elucidated, the clinical aspects of the pineal gland was re-scrutinized. Reviews relating to each of these subjects, as well as many others, are contained in this proceedings book. This volume represents an up-to-date repository for the most recent information related to this rapidly advancing field.