Neuron Vol. 20, 983-993 (1998)
How many subtypes of inhibitory cells in the hippocampus?
1) Laboratoire de Neurobiologie Cellulaire, Institut Pasteur,
25 rue de Dr Roux, 75724 Paris, France 2) Institute
of Experimental Medicine, Hungarian Academy
of Sciences, POB67, H-1450 Budapest, Hungary.
SUMMARY.
Hippocampal inhibitory cells are diverse. It is supposed
that they fall into functionally distinct subsets defined by a similar
morphology and physiology. Switching between functions might be accomplished
by activating receptors for modulating transmitters expressed selectively
by different subsets of interneurons. We tested this hypothesis by
comparing morphology, physiology and neurotransmitter receptor expression
for CA1 hippocampal interneurons. We distinguished 16 distinct morphological
phenotypes and 3 different modes of discharge. Subsets of inhibitory
cells were excited or inhibited by agonists at receptors for NA, muscarine,
5HT and mGluRs. Most cells responded to 2 or 3 agonists and 25 different
response combinations were detected. Subsets defined by morphology,
physiology and by receptor expression did not coincide, suggesting that
hippocampal interneurons cannot easily be segregated into a few well defined
groups.