Spontaneous firing and behavior-related changes in discharge profiles of basal forebrain (BF) neurons are well documented, albeit the mechanisms underlying the variety of activity modes and inter-modal transitions remain elusive. Using cell-attached recordings, this study identifies a range of spiking patterns in diagonal band Broca (DBB) non-cholinergic cells of rats, and tentatively categorizes them into low-rate random, tonic and cluster firing activities. It demonstrates further that the multiplicity of discharge profiles is sustained intrinsically and persists after blockade of glutamate-, glycine/GABA- and cholinergic synaptic inputs. Stimulation of muscarinic receptors, blockade of voltage-gated Ca2+- and small conductance (SK) Ca2+-activated K+ currents (IK+Ca) as well as chelating of intracellular [Ca2+] accelerate low-rate random and tonic firing and favor transition of neurons into cluster firing mode. A similar trend towards higher discharge rates with switch of neurons into cluster firing have been revealed by activation of neuropeptide Y (NPY) receptors with the NPY or NPY1 receptor agonist [Leu31, Pro34]-NPY. Whole-cell current-clamp analysis demonstrates that the variety of spiking modes and inter-modal transitions could be induced within the same neuronal population by injection of bias depolarizing or hyperpolarizing currents. Taken together, these data demonstrate the intrinsic and highly variable character of regenerative firing in BF non-cholinergic cells, subject to powerful modulation by classical neurotransmitters, NPY and small membrane currents.
- Basal forebrain
- spontaneous activity
- Copyright © 2011, Journal of Neurophysiology