[Immunocytochemical characterization of neurosecretory systems producing mesotocin and vasotocin in the brain of several Lacertidae].

Using immunofluorescent techniques vasotocin (VT) and mesotocin (MT) neurosecretory systems were identified in the brain of Lacertidae: one european species and of two south-algerian species. In the 3 species MT and VT was shown to be synthetized in specific neurons located in the anterior preoptic area (POA), the supraoptic (SON) and in the paraventricular (PVN) nuclei. The axons originating in SON and PVN were ending either in the external zone of the rostral median eminence (ME) near to the adenohypophysial portal vessels, or in the neural lobe. In Lacerta muralis the neurosecretory axons of the POA terminated in the vicinity of the vascular organ of the lamina terminalis (OVLT), while in the two desertic species several additional fibers extended more rostrally toward the olfactory peduncle (PO). A short exposure to cold (+ 4 degrees C) of some specimens of Lacerta muralis induced a differential response in the dorsal and ventral parts of the NPV, respectively. Whereas the dorsal part remained unchanged, the ventral part, instead appeared then of essentially composed of small neurons void of secretory granules. Cold exposure also led to a marked accumulation of both MT and VT in the internal zone of the ME, and of VT only, in the external ME zone. On the other hand, a conspicuous amount of MT appeared in adenohypophysial cells.