Barrels of Rats
In rats, each barrel contains approximately 4000 neurons, of which ~10% are inhibitory cells and the remainder are excitatory spiny stellate and small pyramidal cells. Both excitatory and inhibitory neurons are connected recurrently (with cells of the same type, e.g. excitatory to excitatory) and reciprocally (with cells of the other type, e.g., inhibitory to excitatory). There are 250-400 neurons in the corresponding thalamic “barreloid”. These provide afferent input in the form of excitatory thalamocortical synapses onto both types of barrel cells. Thalamic inputs are stronger onto inhibitory cells than onto excitatory ones.
