E of increase in firing rates. (b) During SWRs, basket and bistratified cells strongly increase their firing rate, phase locked to the local oscillation, but axo-axonic cells reduce firing either with or without anaesthesia. Theta field potential, wide band; SWRs, LFP band-pass filtered (90?140; RRx-001 biological activity nonanaesthetised, 90 ?200 or 130?230 Hz) for ripple activity. Scale bars: 0.1 s; action potentials and field potential theta, 0.2 mV; ripples, 0.1 mV. (Data from [15,33,34,40], CA3 bistratified cell without anaesthesia (TJ Viney 2013, unpublished data).)intracellular membrane potential oscillation and the LFP theta is poorly understood. Hippocampal GABAergic interneurons, which provide most of the inhibitory input to pyramidal cells, fire on TGR-1202 molecular weight average at higher rates than pyramidal cells and are also phase locked to the theta rhythm both in freely moving animals [64] and in urethane-anaesthetized preparations (figures 2 and 3). All interneuron types recorded under anaesthesia showed significant theta-modulated firing [31], which we will use below as a surrogate to predict GABA released to the domain of pyramidal cells innervated by a given interneuron type. Most of the time, the rhythmically firing interneuron has a stable phase relationship to the theta field potential, but in awake animals during movement some interneurons also show phase precession for short periods [14,45,61]. In CA1 during anaesthesia, PV-expressing basket cells fire with highest probability on the descending (figures 1 and 2), whereas CCK-expressing basket cells fire on the ascending (figures 1 and 3) phase of theta oscillations in the pyramidal cell layer. The weighted sum of their action potential output is highest at the peak of extracellular theta in the pyramidal layer and lowest at the trough of the LFP [38], thus correlating with the lowest and highest firing probability of pyramidal cells, respectively. However, the firing of bistratified and(a)O-LM cell CA1 anaesth.CA1 theta(b)CA1 ripplesrstb.royalsocietypublishing.org(T64a)CCK+ basket cellsCAPhil. Trans. R. Soc. B 369:anaesth. CA3 CA1 anaesth. CA3 CA1 non-anaesth. anaesth.(T152b)(J69b)CCK+ pp-assoc. cells(T123b)(J55d)ivy cells(T98e)(D26p)Figure 3. Firing patterns related to network activity of CCK-expressing GABAergic neuronal types that collectively innervate the entire somato-dendritic domain of pyramidal cells and of dendrite-innervating O-LM and ivy cells in areas CA1 and CA3 of rat hippocampus. (a) Theta was recorded in the pyramidal layer of CA1. Ivy cells have been reported with and without anaesthesia; note the increase in theta frequency without anaesthesia, and the constant theta firing phase. All cell types, except basket cells in CA1 discharge with maximal probability near the trough of CA1 pyramidal layer theta, when pyramidal cells are most active in both areas under anaesthesia. (b) During SWR oscillations detected in CA1, on average, most cell types shown here in both areas do not change their firing rate; the exception is the perforant path-associated ( pp-assoc.) cells in CA3, which increase their discharge. LFP, as for figure 2. Scale bars: 0.1 s; action potentials and field potential theta, 0.2 mV; ripples, 0.1 mV. (Data from [15,32,34,38,65].)O-LM cells is maximal at the trough of theta (figures 1?), as it is for other interneurons that innervate dendrites, such as double projection (to both septum and retrohippocampal areas), hippocampo etrohippocampal and ivy cells. Accordingly, as GABA relea.E of increase in firing rates. (b) During SWRs, basket and bistratified cells strongly increase their firing rate, phase locked to the local oscillation, but axo-axonic cells reduce firing either with or without anaesthesia. Theta field potential, wide band; SWRs, LFP band-pass filtered (90?140; nonanaesthetised, 90 ?200 or 130?230 Hz) for ripple activity. Scale bars: 0.1 s; action potentials and field potential theta, 0.2 mV; ripples, 0.1 mV. (Data from [15,33,34,40], CA3 bistratified cell without anaesthesia (TJ Viney 2013, unpublished data).)intracellular membrane potential oscillation and the LFP theta is poorly understood. Hippocampal GABAergic interneurons, which provide most of the inhibitory input to pyramidal cells, fire on average at higher rates than pyramidal cells and are also phase locked to the theta rhythm both in freely moving animals [64] and in urethane-anaesthetized preparations (figures 2 and 3). All interneuron types recorded under anaesthesia showed significant theta-modulated firing [31], which we will use below as a surrogate to predict GABA released to the domain of pyramidal cells innervated by a given interneuron type. Most of the time, the rhythmically firing interneuron has a stable phase relationship to the theta field potential, but in awake animals during movement some interneurons also show phase precession for short periods [14,45,61]. In CA1 during anaesthesia, PV-expressing basket cells fire with highest probability on the descending (figures 1 and 2), whereas CCK-expressing basket cells fire on the ascending (figures 1 and 3) phase of theta oscillations in the pyramidal cell layer. The weighted sum of their action potential output is highest at the peak of extracellular theta in the pyramidal layer and lowest at the trough of the LFP [38], thus correlating with the lowest and highest firing probability of pyramidal cells, respectively. However, the firing of bistratified and(a)O-LM cell CA1 anaesth.CA1 theta(b)CA1 ripplesrstb.royalsocietypublishing.org(T64a)CCK+ basket cellsCAPhil. Trans. R. Soc. B 369:anaesth. CA3 CA1 anaesth. CA3 CA1 non-anaesth. anaesth.(T152b)(J69b)CCK+ pp-assoc. cells(T123b)(J55d)ivy cells(T98e)(D26p)Figure 3. Firing patterns related to network activity of CCK-expressing GABAergic neuronal types that collectively innervate the entire somato-dendritic domain of pyramidal cells and of dendrite-innervating O-LM and ivy cells in areas CA1 and CA3 of rat hippocampus. (a) Theta was recorded in the pyramidal layer of CA1. Ivy cells have been reported with and without anaesthesia; note the increase in theta frequency without anaesthesia, and the constant theta firing phase. All cell types, except basket cells in CA1 discharge with maximal probability near the trough of CA1 pyramidal layer theta, when pyramidal cells are most active in both areas under anaesthesia. (b) During SWR oscillations detected in CA1, on average, most cell types shown here in both areas do not change their firing rate; the exception is the perforant path-associated ( pp-assoc.) cells in CA3, which increase their discharge. LFP, as for figure 2. Scale bars: 0.1 s; action potentials and field potential theta, 0.2 mV; ripples, 0.1 mV. (Data from [15,32,34,38,65].)O-LM cells is maximal at the trough of theta (figures 1?), as it is for other interneurons that innervate dendrites, such as double projection (to both septum and retrohippocampal areas), hippocampo etrohippocampal and ivy cells. Accordingly, as GABA relea.