Muscarinic cholinoceptive reticular mechanisms and parabrachial neuron discharge: a novel experimental approach.

This study examined the hypothesis that cholinergic receptor mechanisms within the gigantocellular tegmental field (FTG) of the medial pontine reticular formation can cause state-dependent changes in the firing rates of parabrachial nuclear complex (PBNC) neurons. Using intact, unanesthetized cats, long-term recordings were obtained from single PBNC neurons following FTG administration of cholinergic agonists and antagonists. We show that the state-dependent decrease in PBNC cell discharge reported in this study can be attributed to muscarinic mechanisms within the FTG. Our pharmacological blocking results further suggest that diminished PBNC discharge was mediated by non-M1 muscarinic receptors in the FTG. This study demonstrates the usefulness of combining long-term neuronal recordings in the PBNC with multiple pharmacological manipulations within the FTG.