There may be more to neuronal communication than synapses alone. A study in Nature shows that certain neurons can exert their inhibitory effects without using the specialized intercellular junctions.
Neurogliaform cells - large neurons spreading widely among other types of neuron within the cerebral cortex - release the inhibitory chemical messenger GABA as a large, dense cloud which 'washes over' neighbouring cells. Gábor Tamás and colleagues show that this has a widespread inhibitory effect on nearby neurons, effectively suppressing communication in the local environment without using synapses. This makes neurogliaform cells fundamentally different from other inhibitory neurons, which communicate via synapses and form highly specific circuits.
Extrasynaptic signalling, where neurotransmitters pass on their chemical information by non-synaptic means, has been mooted as a means of neuronal signalling before, but its significance was thought limited. This study shows, in the cerebral cortex at least, that extrasynaptic signalling can yield significant effects. The team further show that neurosteroids can suppress the activity of neurogliaform cells, a finding that may help explain the role of these hormones in post-partum depression and premenstrual syndrome.
Gábor Tamás (University of Szeged, Hungary)
(C) Nature press release.
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