G. Tramu

Ability of the CRF immunoreactive neurons of the paraventricular nucleus to produce a vasopressin-like material. Immunohistochemical demonstration in adrenalectomized guinea pigs and rats.

In the paraventricular nucleus of normal or adrenalectomized colchicine-treated guinea pigs and rats, corticotropin-releasing factor (CRF), vasopressin (VP) and oxytocin (OX) immunoreactivities were compared. In the control animals, respective stainings for these three peptides are distinct. Adrenalectomy resulted in the appearance of a VP-like staining in most of the CRF-immunoreactive neurons whereas OX staining remained distinct. It is suggested that the CRF/VP coexistence reflects the synergistic role of the two peptides.

Extensive Co-localization of neurotensin with dopamine in rat meso-cortico-frontal dopaminergic neurons

In mammalian brain, dopaminergic (DA) cell bodies located in the ventral mesencephalon give rise to meso-cortical, meso-limbic and meso-striatal systems. Among these, the meso-cortical DA pathway is particularly involved in the processing of emotional and cognitive responses. We demonstrate that the rat meso-cortical neurons specifically contain, in addition to DA, another transmitter, Neurotensin. If this co-localization exists in man, it may provide an anatomical substratum for the biological theory of schizophrenia as well as an indication that potential anti-psychotic drugs which act differentially on the DA ascending transmissions can be developed.

Pharmacological study on the mixed CCK8/DA meso-nucleus accumbens pathway: Evidence for the existence of storage sites containing the two transmitters

The mixed CCK8/DA meso-nucleus accumbens pathway was used as a model to study the effects of some pharmacological treatments on the two coexisting transmitters. Reserpine (7 mg/kg i.p.), which depletes monoamine vesicles, induced as early as 1 h following its injection a selective decrease (36%) of CCK8 levels in the posterior part of the nucleus accumbens, an area innervated by the mixed CCK8/DA projection. In contrast, this treatment was without effect on CCK8 levels in the anterior nucleus accumbens and the ventral striatum, two areas which contain distinct CCK8 and DA innervations. Apomorphine (5 mg/kg i.p.), which is known to inhibit the firing rate of DA cells, did not block the reserpine- induced decrease in CCK8 levels suggesting that reserpine is acting on CCK8 storage. This mechanism of action was further substantiated by results obtained with alpha-methyl-p-tyrosine (alpha-MpT, 200 mg/kg i.p.) since no change in CCK8 levels was observed 4 h after this treatment. However, a selective decrease (35%) in CCK8 levels was found in the posterior part of the nucleus accumbens 20 h after two successive alpha-MpT injections. This suggested that long-term interruption of DA transmission resulted in an activation of CCK8/DA cells leading to a release of CCK8. The partial effect of reserpine on total CCK8 stores in CCK8/DA fibers suggests that the peptide is distributed in two types of storage compartments, one of them being sensitive to reserpine and possibly corresponding to mixed CCK8/DA vesicles.

Comparative immunocytochemical localization of enkephalin and somatostatin in the median eminence, hypothalamus and adjacent areas of the guinea-pig brain

Because of the presence of an enkephalin-related substance in the somatostatin terminals of the median eminence, an investigation was carried out on the staining for enkephalin of the somatostatin-containing perikarya localized in the hypothalamic periventricular nucleus. Only an occasional and weak enkephalin immunoreactivity was detected in these perikarya, making the common synthesis of the two peptides unlikely. Moreover, our results demonstrate an enkephalin staining in other fibers of the median eminence clearly distinct from the somatostatin ones. Enkephalin was demonstrated in perikarya distributed in the septum, preoptic area, dorsal and ventromedial hypothalamus, all regions known to possibly project into the median eminence. In none of these sites was enkephalin found in association with somatostatin. The present morphological results support the hypothesis that enkephalins may exert their GH-releasing effect at the hypothalamic level and suggest that enkephalins might directly modulate the somatostatin release into the blood of the portal plexus.

Coexistence of putative neuroactive substances in lateral olivocochlear neurons of rat and guinea pig

We have used the retrograde axonal transport of Fast Blue, injected intra-cochlearly, to identify in the rat lateral superior olive (LSO) neurons which belong to the lateral olivocochlear system (LOCS). Using immunohistofluorescence technique, we have localized within Fast Blue-labeled neurons immunostainings for enkephalins (Met-enkephalin, Met-enkephalin-Arg6-Gly7-Leu8), dynorphins (alpha-neo-endorphin, dynorphin 1-17) or choline acetyltransferase (ChAT). Many Fast Blue-labeled neurons did not show any immunostaining, but all the immunostained neurons found in the LSO were Fast Blue-labeled. In immunohistofluorescence colocalization experiments of two antigens, we could colocalize within the same neurons of the rat LSO immunostainings for ChAT and enkephalins and for ChAT and dynorphins. In each case, neurons only immunostained for ChAT, enkephalins or dynorphins could also be observed. A colocalization of the immunostainings for Met-enkephalin and dynorphins within neurons of the guinea pig and rat LSO was also found. However, in this case, neurons which did not show colocalization were only Met-enkephalin-immunoreactive, thus suggesting that all the dynorphins immunoreactive LSO neurons also contain enkephalins. These findings support the idea that the neurons of the LSO which contain ChAT-, enkephalin- or dynorphin-immunostainings project to the cochlea and belong to the LOCS. It can also be concluded that acetylcholine, enkephalins and dynorphins coexist within a same population of neurons of the LOCS, although other patterns of co-containment of neuroactive substances within LOCS neurons may also exist.

Coexistence of hGHRF and NPY Immunoreactivities in Neurons of the Arcuate Nucleus of the Rat

The distributions of perikarya exhibiting human somatocrinin (hGHRF) and neuropeptide Y (NPY) like immunoreactivities (IR) were compared in the arcuate nucleus of colchicine-treated rats. The majority of hGHRF perikarya was found to exhibit simultaneously NPY IR, while virtually no NPY IR was detected in the external layer of the median eminence. It is suggested that the majority of the hGHRF neurons of the rat arcuate nucleus constitutes a tubero-extra-infundibularly projecting system.

Coexistence of substances related to enkephalin and somatostatin in granules of the guinea-pig median eminence: demonstration by use of colloidal gold immunocytochemical methods

Using two different immunocytochemical approaches at the electron microscopic level, it was shown that substances related to enkephalin and somatostatin coexist in the same granules in the median eminence of the guinea-pig. This finding means that the two neuropeptides are simultaneously released. The possible inhibiting action of enkephalins on somatostatin release is discussed related to other data.

Characterization by different techniques of adrenocorticotropin and gonadotropin producing cells in lerot pituitary (Eliomys quercinus).

SummaryAdrenocorticotropin and gonadotropin producing cells were localized in the adenohypophysis of normal Lerots by using anti-β 1–24 ACTH, anti-LH, anti-LH β, anti PMSG antisera.In order to study their fine structure two techniques were employed: a superimposition technique which consists of detailed comparisons between the same cells in light, fluorescence and electron microscopic preparations and an immunocytochemical technique on ultra-thin sections using the peroxidase anti-peroxidase complex technique.The superimposition technique allows an excellent description of cell ultrastructure of individually identified cells of each type. With this method we were able to desdribe the corticotropin secreting cells as lucent cells with electron dense granules ranging in size from 2500 to 3500 Å.The gondotropin secreting cells are darker and their granules are about 2000 Å in diameter.

Immunohistochemical evidence for an ACTH-like substance in hypothalamic LH-RH neurons.

Abstract A protein immunochemically related to ACTH was detected in guinea pig hypothalamus using antibodies against synthetic 17–39 ACTH. The strict comparison of both anti-17–39 ACTH and anti-LH—RH stainings enabled to conclude that this substance is localized in LH—RH neurons. The presence of a 17–39 ACTH-like substance in hypothalamic neurons agrees with other investigations which indicate that the hypophysis is probably not the sole source of the brain ACTH-like material.

Occurrence and coexistence in Nereis diversicolor O.F. Müller (Annelida Polychaeta) of substances immunologically related to vertebrate neuropeptides.

SummaryNumerous immunochemical and immunohistochemical studies have shown a wide distribution of several families of neuropeptides in invertebrates as well as vertebrates. There are relatively few data available for Annelida: Polychaeta. Therefore, we undertook an immunohistochemical investigation in the marine worm Nereis.Among the vertebrate type antibodies tested, those against met-enkephalin, LH-RH, vasopressin, oxytocin and ACTH had negative or only very slight effects. Slight to moderate reactions were obtained for VIP, SRIF, CRF, GRF, and leu-enkephalin. Moderate to very strong responses were found with anti-CCK/gastrin, -substance P, and -β-MSH sera. Immunopositive reactions were usually observed in the entire CNS (except, until now, in neurosecretory cells, type II, in nuclei 20, and in nerve fibres located in the infracerebral neurohemal area). The immunoreactivity was, however, more or less abundant according to different CNS regions. For example, it appeared that the immunostaining for CRF is more important in the VNC while the leu-enkephalin family is more abundant in the brain (particularly in fuchsinophilic neurosecretory cells, type I, in nuclei 20). Moreover, several vertebrate type peptides (such as CRF/GRF and CCK/gastrin) may coexist in a single neurone. Several antisera may elicit a positive reaction in some specific area (for example, substance P in the nuchal organ; SRIF in oocytes; CCK/gastrin in the gastrointestinal tract).Nothing is known about the role of the different substances immunologically detected in Nereis. It is suggested that CCK/gastrin-, β-MSHand substance P-like materials transmit external stimuli to neurosecretory centres located in the caudal part of the brain.