Abstract: This invention provides methods of identifying a connection between a first neuron and a second neuron or plurality of neurons in a neural tissue slice with a fluorescent indicator. This invention also provides a method of detecting the effect of a neuromodulator on a connection between a first neuron and a second neuron or a plurality of neurons forming a circuit; methods of identifying an inhibitory connection between a first neuron and a second neuron or plurality of neurons; and a method of identifying a connection between a first neuron and a second neuron or plurality of neurons in vivo or in vitro.

Abstract: This invention provides a method of identifying a connection between a first neuron and a second neuron or plurality of neurons comprising of: a) loading neurons in a neural tissue slice with a fluorescent indicator; b) optically detecting an image of the fluorescent indicator-loaded neurons; c) stimulating a first neuron in the neural tissue slice to elicit multiple action potentials from said neuron; and d) optically detecting a change in intensity of the fluorescent indicator in the image at a second neuron or plurality of neurons of the neural tissue slice in response to the multiple action potentials elicited from the first neuron in step (c), wherein detection of a transient decrease in the intensity of the fluorescent indicator in the image at the second neuron or plurality of neurons indicates the activation in the second neuron or plurality of neurons, thereby identifying the connection between the second neuron or plurality of neurons and the first neuron.