High resolution

Module 10: Figure hippocampal input-specific Ca2+ signals

Input-specific Ca2+ signals localized to a single spine.

The diagram on the left illustrates how neuron B can receive different inputs coming from neurons A and C to form input-specific synaptic endings on different spines. When neuron A generates an action potential, it produces localized Ca2+ signals in spines 1, 2 and 3 without any effect on neighbouring spines. The inset illustrates such a localized Ca2+ signal in a single spine (red arrow) in the dendritic region of a CA1 hippocampal neuron (large box in panel a). The panels in b represent 64 ms recordings of Ca2+; note the rapid increase that occurs in a single spine upon a brief stimulation applied at the time of the white asterisk. The average measurements in the spine (small solid box in a) and in a background area (dashed box in a) are shown in c. Summaries of 34 responses are shown in d, which illustrates that not all the stimuli evoked a response, thus illustrating the quantal nature of transmitter release. Reproduced by permission from Macmillan Publishers Ltd: Nature, Mainen, Z.F., Malinow, R. and Svoboda, K. (1999) Synaptic calcium transients in single spines indicate that NMDA receptors are not saturated. 399:151–155. Copyright (1999); http://www.nature.com; see Mainen et al. 1999.