The secretory activity of the subcommissural organ (SCO) is affected by adrenalectomy, adrenalectomy + castration, and by an increase in ambient temperature in adrenalectomized and adrenalectomized + castrated animals. Adrenalectomy inhibits the activity of the SCO. After adrenalectomy + castration the decrease in the secretory activity of the SCO is more rapid. In contrast, an increase in the ambient temperature in adrenalectomized animals induces a recrudescence of the activity of the SCO. The increase in temperature in castrated + adrenalectomized lizards does not affect the inhibition produced by this type of surgical treatment. The histological changes are discussed on the basis of results obtained in the present study and in previous experiments.

This study concerns the subcommissural organ (SCO) of Podarcis s. sicula Raf. in normal and experimentally treated animals. SCO cells present a secretory cycle during the year, with maximum secretion in summer and minimum in winter. SCO secretory activity parallels the sexual cycle in this lizard. The secretory activity of this organ is influenced by all experimental procedures that affect Leydig cells and the SCO. Experimental evidence suggests a relationship between the SCO and the adrenal gland. Indeed, there is an increase in the secretory material of SCO cells with treatment that induces an increase of testosterone or adrenal gland activity in the organism. Vice versa, treatment that leads to a decrease in hormones or that blocks their effects, also brings about a decrease in the amount of secretory material in the SCO.All the data obtained show that both steroid hormones and thermic factors are involved in the control of SCO secretory activity.

In order to study the possible functional relationship between the adrenal gland and the subcommissural organ (SCO) in the lizard Lacerta s. sicula Raf., ACTH was administered to some specimens of this species in January when both the adrenal gland and the subcommissural organ have a very low activity. In comparison to untreated controls, the adrenals of animals treated with ACTH showed clear signs of stimulation, presenting enlarged blood vessels, very few lipid droplets, numerous polymorphic mitochondria and abundant tubular smooth endoplasmic reticulum. In addition, a distinct increase in secretory material was observed in the subcommissural cells of specimens treated with ACTH. These cells showed large cisternae of the rough endoplasmic reticulum filled with granular material in the basal region, numerous secretory granules of two types in the paical region and a reduced number of microvilli on the free cell surface. These findings, together with the results of preceding studies, lead the authors to the consideration that steroid hormones might play a role in the regulation of the secretory activity of the SCO.

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In order to verify the relationships between the SCO and the adrenal, specimens of Lacerta s. sicula were treated with oestrogens during summer, when the adrenal is very active and the SCO cells are filled with secretory material. After oestrogen treatment the interrenal cells appear reduced in size and large blood vessels appear between the interrenal cords. The SCO cells during the first period of treatment show a clear decrease in the amount of secretory material; subsequent treatment restores the levels of secretory material in the SCO cells cytoplasm, which shows an appearance identical to that exhibited by the control specimens of the same period. The results of these experiments point out that adrenal steroidogenic tissue is affected by the action of oestrogen, whose administration causes inactivation of the interrenal tissue with consequences on the SCO activity confirming the existence of a relationship between adrenal gland, interstitial tissue of the testis and SCO, already pointed out by preceding studies carried out in our laboratory.