ABSTRACT
The intact hippocampal formation (IHF) of neonatal or young rats can be kept alive for an extended period in a fully submerged chamber with excellent morphological preservation. Field or patch-clamp recordings, intracellular Ca2+ measurements, and 3-D reconstruction of biocytin-filled neurons can be performed routinely. The generation and propagation of network-driven activities can be studied within the IHF or between connected intact structures such as the septum and the hippocampus or two hippocampi, and the use of a dual chamber enables the application of drugs separately to each structure. This preparation will be useful to study intact neuronal networks in the developing hippocampus in vitro.
Subject(s)
Hippocampus/physiology , Neurons/physiology , 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology , Aging/physiology , Animals , Animals, Newborn , Dissection/methods , Electric Stimulation/methods , Hippocampus/cytology , Hippocampus/drug effects , In Vitro Techniques , Male , Membrane Potentials/drug effects , Neurons/drug effects , Neurons/ultrastructure , Pyramidal Cells/drug effects , Pyramidal Cells/physiology , Pyramidal Cells/ultrastructure , Rats , Rats, Wistar , Tetrodotoxin/pharmacologyABSTRACT
Basic fibroblast growth factor (FGF-2) is expressed in the hippocampus and has been demonstrated to promote neurotrophic effects on hippocampal neurons in vitro. We show that these neurons, even at the embryonic stage, express the mRNAs encoding the FGF receptors, bek and flg. We have characterized the effects of FGF-2 on the expression of nerve growth factor (NGF) using the reverse transcription-coupled polymerase chain reaction, in situ hybridization and immunocytochemistry. In hippocampal neurons grown in the absence of serum, FGF-2 exposure induces an important elevation of NGF mRNA expression followed by a marked increase in NGF immunoreactivity. Combining in situ hybridization with an NGF probe and microtubule-associated protein-2 (MAP2) immunocytochemistry we show that the induction of NGF mRNA by FGF-2 is localized in MAP2-immunoreactive neurons. These results suggest roles for FGF-2 in the development of hippocampal neurons and in the maintenance of connections in the central nervous system, particularly the septo-hippocampal pathway, via the regulation of an important neurotrophin.
