The distribution of vasotocin and mesotocinimmunoreactivity in the hypothalamic magnocellularneurosecretory nuclei of the Saharan herbivorous lizard,Uromastix acanthinurus Bell, 1825 (Sauria-Agamidae)

Abstract

An immunohistochemical study of themagnocellular neurosecretory nuclei was performed inthe hypothalamus of the desert lizard Uromastixacanthinurususing polyclonal antibodies againstarginine vasotocin (AVT), mesotocin (MST) andneurophysins I and II (NpI, NpII). AVT- and MST-immunoreactivities were localized in individual neuronsof the supraoptic, periventricular, and paraventricularnuclei and in scattered neurosecretory cells. Thesupraoptic nuclei (SONs) can be subdivided into rostral,medial and caudal portions. The rostral portion of theSONs was called the SON-ventral aggregation (V SON)because the neurosecretory neurons are present in theventral part of the hypothalamus along the optic chiasma(OC). Their perikarya and fibres were only AVT-ir. Themedial part of the SONs was constituted of two clustersof neurosecretory neurons located in the two lateral endsof the OC to form the SON-lateral aggregations (LSON). In the caudal end of the last one, some MST-irperikarya appeared. The caudal part of the SONs wasconstituted of a dorso-lateral aggregation (D SON) of ir-neurons spreading over the lateral forebrain bundle(LFB). AVT- and MST- perikarya were observed in thiscaudal portion of the SONs, AVT-ir neurons being morenumerous. AVTergic and MSTergic magnocellularneurons were present in the periventricular nuclei(PeVNs). Parvocellular and magnocellular AVT- andMST-ir were observed in the paraventricular nuclei(PVNs). The fibres emerging from the magnocellularneurons which belong to these nuclei and the scatteredcells ran along the hypothalamic floor and entered themedian eminence (ME) to end in the neural lobe ofhypophysis. As a rule, immunoreactivity was alsoobserved in all the regions of the forebrain withvasotocinergic and mesotocinergic perikarya and fibres.The immunoreactive distribution was similar to thatdescribed in other reptiles.