Electrophysiology of ascending, possibly cholinergic neurons in the rat laterodorsal tegmental nucleus: comparison with monoamine neurons.

In urethane-anesthetized rats single neuronal activity was recorded in the laterodorsal tegmental nucleus (LDT), which has a dense complement of cholinergic neurons, and in the dorsal raphe and locus coeruleus for comparison. Most LDT neurons responded antidromically to stimulation of either one or more of several rostral loci, and gave rise to broad spikes. They showed various properties very similar to those of monoaminergic neurons. Others generated brief spikes. The former may be cholinergic. The most frequent response of broad-spike LDT neurons to noxious stimulation was phasic excitation, which tended to become weak or disappear upon repetition.