Distribution of somatostatin immunoreactivityin the brain of the snake Bothrops jararaca

The distribution of perikarya and fibers containing somatostatin was studied in the brain of the snake Bothrops jararaca by means ofimmunohistochemistry using an antiserum against synthetic somatostatin. Immunoreactive perikarya and fibers were localized in telencephalic,diencephalic and mesencephalic areas. In the telencephalon, numerous immunoreactive perikarya were found in the medial,dorsomedial, dorsal and lateral cortex, mainly in the deep plexiform layer, less so in the cellular layer, but not in the superficial plexiformlayer. Immunoreactive perikarya were also observed in the dorsal ventricular ridge, the nucleus of the diagonal band of Broca, amygdaloidcomplex, septum and lamina terminalis. In the diencephalon, labelled cells were observed in the paraventricular, periventricularhypothalamic and in the recessus infundibular nuclei. In the mesencephalon, immunoreactive perikarya were seen in the mesencephalicreticular formation, reticular nucleus of the isthmus and torus semicircularis. Labelled fibers ran along the diencephalic floor and theinner zone of the median eminence, and ended in the neural lobe of the hypophysis. Other fibers were observed in the outer zone ofthe median eminence close to the portal vessels and in the septum, lamina terminalis, retrochiasmatic nucleus, deep layers of the tectum,periventricular gray and granular layer of the cerebellum. Our data suggest that somatostatin may function as a mediator of adenohypophysialsecretion as well as neurotransmitter and/or neuromodulator which can regulate the neurohypophysial peptides in the snakeB. jararaca(

Corticotropin-releasing hormone-like immunoreactivity inthe brain of the snake Bothrops jararaca

The distribution of corticotropin-releasing hormone in the brain of the snake Bothrops jararaca was studied immunohistochemically. Immunoreactive neurons were detected in telencephalic, diencephalic and mesencephalic areas such as dorsal cortex, subfornical organ, paraventricular nucleus, recessus infundibular nucleus, nucleus of the oculomotor nerve and nucleus of the trigeminal nerve. Immunoreactive fibres ran along the hypothalamo-hypophysial tract to end in the outer layer of the median eminence and the neural lobe of the hypophysis. In general, immunoreactive fibres occurred in the same places of immunoreactive neurons. In addition, immunoreactive fibres were observed in the septum, amygdala, lamina terminalis, supraoptic nucleus, nucleus of the paraventricular organ, ventromedial hypothalamic nucleus and interpeduncular nucleus. These results indicate that, as for other vertebrates, corticotropin-releasing hormone in B. jararaca brain, besides being a releasing hormone, may also act as a central neurotransmitter and/or neuromodulator.

The distribution of vasotocin and mesotocin immunoreactivity in the brain of the snake, Bothrops jararaca

Polyclonal antibodies against vasotocin (AVT) and mesotocin (MST) were used to explore the distribution of these peptides in thebrain of the snake Bothrops jararaca . Magnocellular AVT- and MST-immunoreactive (ir) perikarya were observed in the supraopticnucleus (SON), being AVT-ir neurons more numerous. A portion of the SON, in the lateroventral margin of the diencephalonventrally to optic tract, showed only AVT-ir perikarya and fibers. However, the caudal most portion displayed only mesotocinergicperikarya. Parvocellular and magnocellular AVT- and MST-ir perikarya were present in the paraventricular nucleus (PVN) beingAVT-ir fibers more abundant than MST-ir. Vasotocinergic perikarya were also found in a dorsolateral aggregation (DLA) far fromthe PVN. Mesotocinergic perikarya were also present in the recessus infundibular nucleus and ependyma near to paraventricularorgan. Nerve fibers emerging from supraoptic and paraventricular nuclei run along the diencephalic floor, internal zone of themedian eminence (ME) to end in the neural lobe. Also a dense network of AVT- and MST-ir fibers was present in the external zoneof the ME, close to the vessels of the hypophysial portal system. As a rule, all regions having vasotocinergic and mesotocinergicperikarya also showed immunoreactive fibers. Vasotocinergic and mesotocinergic fibers but not perikarya were found in the laminaterminalis (LT). Moreover AVT-ir fibers were present in the nucleus accumbens and MST-ir fibers in the septum. In mesencephalonand rhombencephalon MST-ir fibers were more numerous than AVT-ir fibers. Vasotocinergic and mesotocinergic fibers inextrahypothalamic areas suggest that these peptides could function as neurotransmitters and/or neuromodulators in the snake B.jararaca.