IN-VIVO ELECTROPHYSIOLOGICAL DISTINCTION OF HISTOCHEMICALLY-IDENTIFIED CHOLINERGIC NEURONS USING EXTRACELLULAR RECORDING AND LABELING IN RAT LATERODORSAL TEGMENTAL NUCLEUS
Y. Koyama et al., IN-VIVO ELECTROPHYSIOLOGICAL DISTINCTION OF HISTOCHEMICALLY-IDENTIFIED CHOLINERGIC NEURONS USING EXTRACELLULAR RECORDING AND LABELING IN RAT LATERODORSAL TEGMENTAL NUCLEUS, Neuroscience, 83(4), 1998, pp. 1105-1112
From indirect evidence we have proposed that cholinergic versus non-ch
olinergic neurons in the laterodorsal tegmental nucleus can be disting
uished with the duration of their extracellularly recorded action pote
ntials, ''broad'' spikes for the former, ''brief'' for the latter. To
rest this assumption more directly, we labelled single neurons recorde
d extracellularly in and around the laterodorsal tegmental nucleus wit
h biocytin or neurobiotin, and processed the sections with reduced nic
otinamide adenine dinucleotide phosphate-diaphorase, a proven marker f
or cholinergic neurons in the laterodorsal tegmental nucleus. Biocytin
or neurobiotin which was deposited at the site of recording was incor
porated into single neurons. Among 171 trials (91 for broad-spike and
80 for brief-spike neurons), marking was successful in 68 cases (29 fo
r broad-spike and 39 for brief-spike neurons). Almost all (21/22) of t
he broad-spike neurons located within the laterodorsal tegmental nucle
us were positive for reduced nicotinamide adenine dinucleotide phospha
te-diaphorase staining, i.e. they were cholinergic, while all of the b
rief-spike neurons in and outside of the laterodorsal tegmental nucleu
s lacked the diaphorase activity, and were thus non-cholinergic. The p
resent study shows that, after extracellular labelling of single neuro
ns by biocytin or neurobiotin, cholinergic neurons in the laterodorsal
tegmental nucleus are confidently distinguished from non-cholinergic
ones in the corresponding area with their spike shapes. It is also sho
wn that the cholinergic neurons distinguished by this criterion are ch
aracterized by their tonic firing at slightly lower rate and larger ce
ll size than the brief-spike non-cholinergic ones. (C) 1998 IBRO. Publ
ished by Elsevier Science Ltd.