Brain distribution and evidence for both central and neurohormonal actions of cocaine- and amphetamine-regulated transcript peptide in Xenopus laevis.

We tested the hypothesis that, in the amphibian Xenopus laevis, cocaine- and amphetamine-regulated transcript peptide (CARTp) not only has widespread actions in the brain but also acts as a local factor in endocrine pituitary cells and/or is neurohemally secreted into the circulation to control peripheral targets. CARTp-immunoreactive cells occur in the olfactory bulb, nucleus accumbens, amygdala, septum, striatum, nucleus of Bellonci, ventrolateral nucleus, central thalamic nucleus, preoptic nuclei, and suprachiasmatic nucleus, and particularly in the medial pallium, ventromedial nucleus, hypothalamus, Edinger-Westphal nucleus, optic tectum, raphe nuclei, central gray, nucleus of the solitary tract, and spinal cord. From the hypothalamic magnocellular nucleus, CARTp-containing axons run to the neurohemal median eminence, and to the neural pituitary lobe to form neurohemal terminals, as shown by immunoelectron microscopy.

Brain-derived neurotrophic factor in the hypothalamo-hypophyseal system of Xenopus laevis.

Brain-derived neurotrophic factor (BDNF) is immunocytochemically demonstrated in the magnocellular nucleus and neural lobe of the pituitary gland of the amphibian Xenopus laevis. Immunoelectron microscopy shows BDNF in secretory granules of type A neurohemal axon terminals in the neural lobe of pituitary gland. It is proposed that BDNF released from the neural lobe acts as a neurohormone stimulating the secretory activity of the melanotrope cells in the intermediate pituitary lobe.

Opioid peptides, CRF, and urocortin in cerebrospinal fluid-contacting neurons in Xenopus laevis.

The presence of the opioids, beta-endorphin, met-enkephalin, and endomorphin, and of corticotropin-releasing factor (CRF) and the CRF family member, urocortin (Ucn), is described in cerebrospinal fluid-contacting neurons in the brain of the amphibian, Xenopus laevis.

Evidence that urocortin I acts as a neurohormone to stimulate alpha MSH release in the toad Xenopus laevis.

We have raised the hypothesis that in the South African clawed toad Xenopus laevis, urocortin 1 (UCN1), a member of the corticotropin-releasing factor (CRF) peptide family, functions not only within the brain as a neurotransmitter/neuromodulator but also as a neurohormone, promoting the release of alpha-melanophore-stimulating hormone (alphaMSH) from the neuroendocrine melanotrope cells in the intermediate lobe of the pituitary gland. This hypothesis has been investigated by (1) assessing the distribution of UCN1 and CRF by light immunocytochemistry, (2) determining the subcellular presence of UCN1 in the neural lobe of the pituitary gland by immuno-electron microscopy applying high-pressure freezing and cryosubstitution, and (3) testing the effect of UCN1 on MSH release from toad melanotrope cells using in vitro superfusion. In the X.

Immunohistochemical localization of cocaine- and amphetamine-regulated transcript peptide in the central nervous system of the frog Rana esculenta.

The distribution of cocaine- and amphetamine-regulated transcript peptide (CARTp)- like immunoreactivity was studied only in the rat central nervous system (CNS). In mammals, CART peptides occur among others in brain areas that control feeding behavior. We mapped CARTp-immunoreactive structures in the CNS of the frog Rana esculenta and assumed that differences may exist in the CARTp-containing neuronal populations between the frog, which does not feed in winter, and the rat.

Role of cortical filamentous actin in the melanotrope cell of Xenopus laevis.

In secretory cells filamentous actin (f-actin) is mostly present subjacent to the plasma membrane, referred to as cortical actin. While the function of cortical actin in the secretory processes has been extensively studied, little attention has been given to the role of actin in signal transduction and intracellular second messenger dynamics. Analysis with the fluorescent f-actin probe Alexa-phalloidin shows that Xenopus laevis pituitary melanotrope cells possess a thick cortical actin ring.