Jacqueline Besson

Vasoactive intestinal peptide (VIP): Brain distribution, subcellular localization and effect of deafferentation of the hypothalamus in male rats

Abstract We have studied the regional and subcellular distribution of vasoactive intestinal peptide (VIP) in the brain of adult male rat, using a specific radioimmunoassay. Selective deafferentation of the mediobasal hypothalamus (MBH) was also performed in order to investigate the origin of hypothalamic VIP. The highest concentrations of VIP were found in the neocortex, namely the occipital region. The brain stem, the posterior hypothalamus, and the pineal gland contained low amounts of the peptide. VIP was not detectable in the cerebellum and the neurohypophysis. After fractionation, most of the VIP was recovered from the crude mitochondrial fraction of the hypothalamus as well as the parietal cortex. However, a non-negligible portion of the activity was also found in the supernatant suggesting that the peptide is mainly located in nerve endings but also present in neuronal cell bodies and/or axons. Two weeks after complete deafferentation of the MBH, VIP concentrations of the caudal MBH (including the infundibular sulcus, the stalk, part of the ventromedial nucleus and premamillary structures) were decreased by 40%. In contrast, no change in VIP levels were observed in the rostral MBH, organum vasculosum of the lamina terminalis (OVLT), and cortex. This suggests that hypothalamic nerve endings containing the peptide derive from neuronal cell bodies located both outside and within the MBH.

Characterization and autoradiographic distribution of vasoactive intestinal peptide binding sites in the rat central nervous system.

Biochemical characteristics and topographical distribution of mono-[125I )vasoactive intestinal peptide (VIP) binding sites in rat brain were studied on tissue sections and by quantitative autoradiography. Biochemical investigations show two classes of binding sites with a dissociation constant of 1.03 +/- 0.11 nM and 68 +/- 14 nM and a maximal binding capacity of 43.3 +/- 5.1 fmol/mg protein and 713 +/- 117 fmol/mg protein respectively. The order of potency of various peptides to inhibit 125I-VIP binding to brain sections is: VIP greater than PHI greater than secretin greater than VIP greater than hGRF. Autoradiography reveals the highest densities of binding sites in the pineal gland, the dentate gyrus of the hippocampus, the central amygdaloid nucleus and in various thalamic nuclei such as the mediodorsal, lateral posterior, submedius, dorsolateral and medial geniculate nuclei. Similar high densities are observed in the olfactory bulbs as well as in the suprachiasmatic and dorsomedial nuclei of the hypothalamus and in the superior colliculus. These data together with the distribution of the endogenous peptide suggest a physiological role for VIP both in the regulation of CNS activities and pituitary functions.

Vasoactive intestinal peptide inhibits release of somatostatin from

The effect of vasoactive intestinal peptide (VIP) was studied on the release of somatostatin (SRIF) from slices of several regions of the rat brain in vitro. VIP induced a dose-dependent inhibition of SRIF release from mediobasal hypothalamic slices but did not interfere with SRIF release from preoptic area, amygdala or cortex. VIP Inhibition had an apparent affinity: Kd = 6.8 ± 3.9 × 10−11 M. Secretin has a similar effect but at 600-fold higher concentrations (Kd secretin = 4.2 ± 0.6 × 10−8 M). Glucagon was ineffective in concentrations ranging from 10−10 M to 10−7 M. The data are consistent with a role of VIP in the hypothalamic control of growth hormone secretion.

A new neuroregulator: The vasoactive intestinal peptide or VIP

VIP is a neuroregulator occurring in the central and peripheral nervous system which exhibits the function of neurotransmitter in the brain, neuroendocrine substance at the pituitary level, and neuroparacrine substance in peripheral organs. The structure and the specificity of the molecule as studied by antibody and receptor, and its location in brain and peripheral organs are summarized as well as its numerous biological effects. The method used to demonstrate the involvement of VIP in a physiological regulation is described and illustrated by two examples: the effect of VIP on gut epithelium and the neuroendocrine action of VIP in inducing prolactin release from pituitary cells. The consequence of this recent progress in the knowledge of VIP release and action in human physiology and disease is indicated.

In vitro autoradiographic localization of vasoactive intestinal peptide (VIP) binding sites in the rat central nervous system

This paper describes the autoradiographic distribution of VIP binding sites in the rat central nervous system using monoiodinated 125I-labeled VIP. High densities of VIP binding sites are observed in the granular layer of the dorsal dentate gyrus of the hippocampus, the basolateral amygdaloid nucleus, the dorsolateral and median geniculate nuclei of the thalamus as well as in the ventral part of the hypothalamic dorsomedial nucleus.

Ontogeny of vasoactive intestinal peptide and somatostatin in different structures of the rat brain: effects of hypo- and hypercorticism

The ontogeny of the vasoactive intestinal peptide (VIP) and somatostatin (SRIF) was studied in various structures of the rat central nervous system (CNS), using specific radioimmunoassays. The effect of adrenal corticoids on the concentration of both peptides was investigated during the development of the rat from 3 days before birth to 2 months after birth. The evolution of both peptides was different since SRIF was found before birth in each structure tested while VIP appeared only after birth in the same structures. However, after birth the ontogeny of VIP and SRIF was quite similar and the maximum concentration of both peptides occurred between day 14 and day 21. Hypercorticism (implant of corticosterone) and hypocorticism (Metyrapone injections) modified the postnatal evolution of both peptides, suggesting that corticoids play an important role in the brain developmental patterns of VIP and SRIF.

Distribution of vasoactive intestinal polypeptide in intact, stria terminalis transected and cerebral cortex isolated rats.

Recent radioimmuno-2,5,6,s,15,16 and immunocytochemicalS, 13,17 studies have clarified the cerebral localization of vasoactive intestinal polypeptide (VIP). VIP proved to be present in almost every major anatomical unit of the brain. Its distribution is uneven with the highest concentration in the cerebral cortex where it is found in perikarya (mainly in layers II-III) fibres and nerve terminalsS,18,17. The amygdala, suprachiasmatic nucleus and midbrain central gray matter were also shown to contain VIP immunopositive cells s,17. VIP was determined in several limbic, extrapyramidal and brain stem areas. To decide whether cortical VIP is extrinsic, VIP was measured one week after the undercutting of the cortex. The stria terminalis is known to contain VIP-fibres8,13A4,17. The transection of this pathway was aimed at elucidating the origin of abundant VIP-fibres found in the amygdala and some hypothalamic regions. CFY-strain male rats of 200 410 g b. wt. were kept under standard conditions (24 41 °C, 7 0 ~ humidity, 12-12 h light-dark periods, normal food, tap water ad libitum). Intact and operated animals were killed by decapitation at 08.00-09.00 h. Brains were frozen on dry-ice and cut in the coronal plane in a -10 °C cryostat. Section thickness was 300/~m. Using the micropunch technique 10 samples were taken from 8 brain areas (listed in Tables). Each sample was homogenized either in 120/~10.1 N HC1 or in 120/~1 0.1 N perchloric acid. From 5 #1 of the homogenates, protein was determined 9. VIP-concentration was measured by a specific radioimmunoassay 1. The VIP antiserum was raised in rabbits against natural porcine VIP coupled to bovine serum albumin. It exhibited no cross-reactivity with substance P, neurotensin, enkephalins, endorphins, LH-RH, somatostatin and glucagon.

Autoradiographic localization of vasoactive intestinal peptide (VIP) binding sites in the human term placenta. Relationship with activation of adenylate cyclase

The presence of vasoactive intestinal peptide (VIP) binding sites and the adenylate cyclase activity in response to VIP were examined in the human term placenta. Slices were used in order to preserve the physicochemical environment and the structural integrity of this heterogeneous organ. 125I-VIP binding to placental slices was saturable. The steady state was reached after 90 min at 37 degrees C and was maintained up to 3 h. Unlabeled VIP was able to compete in a dose-dependent manner with an IC50 value of 5.2 +/- 1.3 x 10(-10) M. Autoradiography and histological analysis showed that VIP binding sites were essentially located on fetal vascularization, especially arteries of stem villi. VIP produced a stimulatory effect on cAMP synthesis at a concentration as low as 10(-10) M. The dose-response curve was monophasic with an ED50 value of 2.9 +/- 1.6 x 10(-9) M. The specificity of the VIP effect was tested with peptides structurally related to VIP such as glucagon, secretin, gastric inhibitory polypeptide and human growth-hormone releasing factor. Only secretin at high concentrations (greater than 10(-6) M) increased cAMP production. Leu-enkephalin or insulin were ineffective. The presence of both VIP binding sites on fetal vascularization and VIP-induced adenylate cyclase activation would seem to suggest a regulatory role of the peptide on fetoplacental blood flow.

Vasoactive intestinal polypeptide: Presence in neuroblastoma × glioma hybrid cells

Abstract Extracts of neuroblastoma × glioma hybrid cells 108CC15 and their parental lines were investigated for the presence of vasoactive intestinal polypeptide (VIP). With the aid of a radioimmunoassay and a receptor binding assay, VIP activity was found in the hybrid cells, to a lesser extent in neuroblastoma cells, but not in glioma cells, but not in glioma cells. These results suggest a neuronal function of VIP. Since the hybrid cells also contain acetylcholine and opioids, they may be useful in studies of co-release of neurohormones.

Vasoactive intestinal peptide (VIP) receptors positively coupled with adenylate cyclase activity in the human placenta: Vascular localization

Summary The presence of Vasoactive Intestinal Peptide (VIP) has been reported in human placenta, a non-innervated organ. However, the exact origin of this neuropeptide, the precise localization of its binding sites, and the mechanism(s) of action remain tobe clarified. The 125 I-VIP binding to placental slices was saturable, and unlabeled VIP was able to compete in a dose-dependent manner with an IC 50 value of 5.2±1.3×10 −10 M. Light microscopic autoradiography on placental slices showed the association of high densities of labeling with blood vessel pathways, especially arteries of stem villi. When sections were treated by high resolution autoradiography, all cellular components contained silver grains, although a much higher density of labeling was associated with blood vessels, especially with endothelial cells. Consequently, adenylate cyclase activity was studied on placental slices and on isolated membranes of stem villi vessels. On placental slices, VIP produced a stimulatory effect of cAMP synthesis at a concentration as low as 10 −10 ×M. The dose response curve was monophasic with an ED 50 value of 2.9±1.6×10 −9 M. The specificity of the VIP effect was tested with peptides structurally related to VIP such as glucagon, secretin, gastric inhibitory polypeptide, and human growth hormone releasing factor. Only secretin in high concentrations (>10 −6 M) increased cAMP production. Leu-enkephalin or insulin were ineffective. Furthermore, the VIP stimulated, specifically and in a dose dependent manner, the adenylate cyclase activity of vascular membranes. These results confirm the presence of VIP receptors positively coupled with adenylate cyclase on the fetal vascularization and suggest a functional role for the peptide in placental hemodynamics.