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Fig. 3
Connections between FF inhibitory neurons on the two sides.
(A) Patching of pairs of FF neurons on opposite sides of the brain. In this case, firing the right cell (Right FF) led to an IPSP in the FF on the left side (Left FF) (middle panel), but the left cell did not produce a response in the right one (right panel). B1 and B2 show horizontal and cross sections respectively, of the neurons recorded in A after filling them with dye. Green processes from the right neuron give rise to swellings apposed to the left neuron (arrowheads on insets in B1,B2, which show the soma at higher magnification), consistent with the physiological connection. (C) Paired patch recordings of two reciprocally connected FF neurons. Firing the right neuron led to a depolarizing response in the left cell and vice versa (dark traces). Both responses were blocked by strychnine (1 µM, gray traces), consistent with the PSP being a glycinergic inhibition with a reversal potential just above resting potential in our recording conditions. (D1–2) The locations of the neurons recorded in C in confocal images of the dye filled neurons after recordings. (E1) Patching of 17 bilateral pairs of FF neurons from either 4 day (relaxed) or 6 day (nacre) old fish revealed that most were connected to each other in one or both directions. Numbers in the histograms indicate the number of pairs with connections in neither direction (none), one direction (1-way), or reciprocal connections (2-way). (E2) Box plot of the strengths of the connections from left to right and right to left (only measured in cases where there was a connection in a given direction). The connection strengths were not significantly different in the two directions.