Electrophysiological Properties of Pyramidal Neurons in the Rat Prefrontal Cortex: An In Vivo Intracellular Recording Study

Abstract

In order to determine the electrophysiological properties of prefrontal cortex pyramidal neurons in vivo, intracellular recordings coupled with neurobiotin injection were performed in anesthetized rats. Three main classes of pyramidal cells were distinguished according to both their firing patterns in response to depolarizing current pulses and the characteristics of their action potentials: regular spiking (RS, n = 71); intrinsic (inactivating) bursting (IB, n = 8); and non-inactivating bursting (NIB, n = 26) cells. RS cells were further subdivided into slow-adapting and fast-adapting types, according to their firing frequency adaptation. IB and fast-adapting RS cells could exhibit different firing patterns depending on the intensity of the depolarizing current. In response to successive depolarizing pulses of a given intensity, NIB and some RS cells showed variations in their firing patterns, probably due to the impact of local synaptic activity. All the labeled neurons were pyramidal cells with an apical dendrite that formed a terminal tuft in layer I. As compared to RS cells, NIB cells had a smaller somatic size and their apical dendritic tuft was less extensive, while IB cells presented a larger somatic size, thicker dendrites and a wider extent of their basal and apical dendritic arborization. In conclusion, we found in the rat prefrontal cortex, in vivo, different electrophysiological classes of pyramidal cells whose output firing patterns depend on interactions between their intrinsic properties and the ongoing synaptic activity.

Cortical energy demands of signaling and nonsignaling components in brain are conserved across mammalian species and activity levels

“…Cortical signaling requirements dominated energy demand in the awake state, whereas nonsignaling requirements were ∼20% of awake value. These predictions are supported by 13 C magnetic resonance spectroscopy results. We conclude that mitochondrial energy support for signaling and nonsignaling components in cerebral cortex are conserved across activity levels in mammalian species.…”

“…Cerebral energy demand is also positively correlated with the rate of pyramidal neuron firing in rat cortex (4,5). 13 C MRS findings in the human cortex have been generally consistent with the rat results (6). However, there remain questions as to how well the energy costs of specific subcellular processes needed to support synaptic transmission and conduction are conserved over different activity levels and/or across species.…”

“…S1) and the average neuronal (η N ) and astrocytic (η A ) densities in the cerebral cortex (Table 1). Because recent R in,x and η x measurements in the rat show that values for neurons and astrocytes are quite similar (13)(14)(15)(16), the calculations were slightly simplified by assuming that R in,N ∼ R in,A and η N ∼ η A (Table 1 and SI Text, section 2). To determine P ns , we needed the metabolic demand for nonsignaling, which was possible for the rat, because state of deep pentobarbital anesthesia in Table S1 …”

“…13 C magnetic resonance spectroscopy (MRS) in the rat has shown that, in the resting awake state, ∼80% of cortical energy consumption is used to support signaling as reflected by the rate of glutamate neurotransmitter release and astroglial uptake (2,3). Cerebral energy demand is also positively correlated with the rate of pyramidal neuron firing in rat cortex (4,5).…”

The Rostral Medial Prefrontal Cortex Regulates the Expression of Conditioned Eyelid Responses in Behaving Rabbits

“…With regard to their firing properties, most neurons recorded and analyzed appeared to be similar to the regular-spiking, slowadapting pyramidal cells described by Dégenètais et al (2002); that is, they were capable of generating a tonic firing during the CS-US interval when CRs were generated (see below). Figure 3A-C shows representative examples of rmPFC neurons recorded during the classical eyeblink conditioning study.…”