Fig. 4.

Preliminary data showing that β1-AR stimulation increases the firing of a small subset of FS neurons and reduces the firing of RS neurons in dlPFC

(A) The ODR working memory task, (B) The iontophoretic electrode: a carbon fiber and surrounding glass micropipettes for drug delivery, with a tip diameter of around 40 μm. (C) The dlPFC recording site (PS = principal sulcus; AS = arcuate sulcus). The insert shows waveforms of regular spiking (RS) and fast spiking (FS) neurons. (D) An example of a regular spiking Delay cell, with sustained delay-related firing for its preferred direction only. (E-G) show that xamoterol decreased the firing of regular spiking neurons (n = 11), reducing firing rate (E, F, delay firing: R-two-way ANOVA, F_{directionxdrug}(1, 10) = 13.448, p = 0.0043; Sidak's multiple comparisons: preferred direction, p < 0.0389 and non-preferred direction, p = 0.7599) and spatial tuning (G, paired t-test, n = 11, P = 0.000591). The dark grey area, Cue epoch; light grey area, Delay epoch. (H-J) show that xamoterol also reduced the firing rate of most fast spiking neurons, reducing both firing rate (H, I delay firing: R-two-way ANOVA, F_{directionxdrug}(1, 4) = 27.696, p = 0.0062; Sidak's multiple comparisons: preferred direction, p < 0.0342 and non-preferred direction, p = 0.33) and spatial tuning (J, paired t-test, P = 0.0363). (K-M) A single cell example of a fast spiking neuron that showed increased firing with xamoterol, showing that both its delay-related firing (K, L, control vs. xamoterol@40 nA condition: two-way ANOVA, F_{directionxdrug}(1,13) = 1.58, p = 0.2555; F_drug(1,13) = 8.499, p = 0.0268; F_direction (1,13) = 17.39, p = 0.0059; Sidak's multiple comparisons: preferred direction, p = 0.0163 and non-preferred direction, p = 0.73), and spatial tuning (M) were increased by xamoterol. The neuron did not return to control levels of firing after xamoterol was washed out, suggesting potential second messenger actions.