Development of cholinergic and GABAergic neurons in the rat medial septum: Different onset of choline acetyltransferase and glutamate decarboxylase mRNA expression

Abstract

In the present study, we have investigated the developmental expression of the transmitter-synthesizing enzymes choline acetyltransferase (ChAT) and glutamate decarboxylase (GAD) in rat medial septal neurons by using in situ hybridization histochemistry. In addition, we have employed immunostaining for ChAT and the calcium-binding protein parvalbumin, known to be contained in septohippocampal GABAergic neurons. A large number of GAD67 mRNA-expressing neurons were already observed in the septal complex on embryonic day (E) 17, the earliest time point studied. During later developmental stages, there was mainly an increase in the intensity of labeling. Neurons expressing ChAT mRNA were first recognized at E 20, and their number slowly increased during postnatal development of the septal region. The adult pattern of ChAT mRNA-expressing neurons was observed around postnatal day (P) 16. By using a monoclonal ChAT antibody, the first immunoreactive cells were not seen before P 8. Similarly, the first weakly parvalbumin-immunoreactive neurons were seen in the septal complex by the end of the 1st postnatal week. These results indicate that in situ hybridization histochemistry may be an adequate method to monitor the different development of transmitter biosynthesis in cholinergic and GABAergic septal neurons. Moreover, the late onset of ChAT mRNA expression would be compatible with a role of target-derived factors for the differentiation of the cholinergic phenotype.

Newly identified patterns of Pax2 expression in the developing mouse forebrain

“…To gain further insight into the neurochemical properties of the differentiated Pax2 cells detected in the septum, we examined co-expression of Pax2 and markers of GABA-ergic and cholinergic neurons, the principal neuronal types of this structure [ 28 - 30 ].…”

Nerve Growth Factor Rapidly Increases Muscarinic Tone in Mouse Medial Septum/Diagonal Band of Broca

“…One set of experiments used p75 NTRϪ/Ϫ mice (Lee et al, 1992). During postnatal development in rat, the septohippocampal system acquires the adult pattern at approximately postnatal day 14 (Milner et al, 1983;Linke and Frotscher, 1993;Linke et al, 1995;Bender et al, 1996). Although similar information is limited for mouse Hagg, 1999, 2000;Clancy et al, 2001), it has been reported that the developmental schedule of the mouse CNS precedes that of the rat by ϳ2 d. According to this timetable, the slices used for experiments in this study were derived from mice when the septohippocampal system is in a relatively mature state.…”

A Novel Type of GABAergic Interneuron Connecting the Input and the Output Regions of the Hippocampus

“…In situ hybridization was performed by using free-floating sections. They were incubated for 10 -18 hr at 47°C in hybridization buffer containing 50% formamide, 4ϫ SSC, 250 g /ml denatured salmon sperm DNA, 100 g /ml yeast tRNA, 5% dextran sulfate, 1ϫ Denhardt's solution (Sigma), and the probe (sense or antisense, diluted 1:1000; Bender et al, 1996). After posthybridization washes (2ϫ SSC for 2 ϫ 15 min at 24°C, 2ϫ SSC /50% formamide for 15 min at 57°C, 0.1 SSC /50% formamide for 15 min at 57°C, and 0.1ϫ SSC for 15 min at 57°C), labeled neurons were detected by a digoxigenin -RNA labeling and detection kit (Boehringer Mannheim, Mannheim, Germany).…”