A simple method for coupling in situ hybridization and immunocytochemistry: application to the study of peptidergic neurons.

We have devised a simple procedure for immunostaining of sections that have previously undergone autoradiographic visualization of mRNAs by in situ hybridization. Classical hybridocytochemistry techniques were performed first on cryostat sections of formaldehyde-fixed tissue. Standard methods were used for slide coating by emulsion dipping and for revelation, fixation, and coverslipping steps. The key to this method is the emulsion removal, or permeabilization, by a short trypsin incubation (0.2% for 20-30 sec) which facilitates the good access of antibodies used in a subsequent immunocytochemical technique to section epitopes. Usual immunofluorescence and immunoperoxidase procedures were successfully performed after this treatment. The immunoreactivity of several neuropeptides was well preserved after this procedure. In addition to its usefulness in our studies, this general method should be applicable to many other situations in which autoradiographic and immunocytochemical detections must be coupled.

Cloning of cDNAs encoding a rat neuropeptide immunologically related to salmon melanin-concentrating hormone.

In order to identify the neuropeptide related to melanin-concentrating hormone (MCH) synthetized by neurons of the posterior hypothalamus in the mammals, we have screened rat hypothalamus and rat brain cDNA expression libraries using MCH antiserum. We isolated 5 distinct immunopositive recombinants with cross-hybridizing cDNA inserts. One of them hybridized to RNAs exclusively located in neurons stained by the same antiserum, as seen by successively performing in situ hybridization and then an immunocytochemical technique on the same section. Sequencing of this MCH-like cDNA is in progress.

[Specific hybridization of a synthetic oligonucleotide in rat hypothalamic neurons immunoreactive to immune serum against salmon melanin-concentrating hormone]. / Hybridation spécifique d'un oligonucléotide de synthèse dans les neurones hypothalamiques du rat immunoréactifs à un immunsérum dirigé contre l'hormone de mélanoconcentration du saumon.

An oligonucleotide probe corresponding to the 9 C-terminal residues encoded by a complementary DNA of a rat peptide related to salmon melanin concentrating hormone (MCH) was synthetized. It specifically hybridized to the neurons stained by antisera to MCH in the rat posterior hypothalamus, as seen by coupling in situ hybridization and immunocytochemical methods. This result validates our sequence determination. This oligonucleotide will be useful to establish the complete sequence of the rat MCH precursor molecule. It will also constitute a valuable tool to study physiological or experimentally-induced changes in the expression of the rat MCH gene.

[Cloning of the cDNA, while encoding a hypothalamic neuropeptide in the rat, related to the melanin-concentrating hormone in the salmon]. / Clonage d'un ADNc codant un neuropeptide hypothalamique de rat apparenté à l'hormone de mélano-concentration du Saumon.

In order to identify the neuropeptide related to salmon melanin-concentrating hormone (MCH) synthetized by neurons of the posterior hypothalamus in the mammals, we have screened rat hypothalamus and rat brain cDNA expression libraries using MCH antiserum. Five recombinants were isolated, which cDNAs were amplified using the polymerase chain reaction. One of them hybridized to RNAs exclusively located in hypothalamic neurons stained by the same antiserum, as seen by performing in situ hybridization and immunocytochemical techniques on the same section. The sequence analysis showed that this cDNA corresponds to the end of the open reading frame encoding a MCH-like peptide and to the 3' untranslated region. The rat MCH is very similar to salmon MCH (greater than 85% homologies in the 14C-terminal residues).