Electrophysiological Properties of Pyramidal Neurons of Rat Prefrontal Cortex

[Chip (OP)]

source: https://academic.oup.com/cercor/article/12/1/1/359215

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 = ; 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.

Electrophysiological Properties of Pyramidal Neurons in the Rat Prefrontal Cortex: An In Vivo Intracellular Recording Study [January 2002]

Introduction

The prefrontal cortex (PFC) is involved in higher cognitive functions such as working memory, temporal ordering events, organization and planning of responses (Goldman-Rakic, 1995a,1995b; Seamans et al., 1995; Floresco et al., 1997; Fuster, 1997). Among various mammalian species, the PFC is defined as the cortical region that receives its main thalamic inputs from the mediodorsal nucleus of the thalamus (Rose and Woolsey, 1948; Groenewegen, 1988). The PFC is connected with associative cortical areas and with subcortical structures of the extrapyramidal and limbic systems (Uylings and Van Eden, 1990) and is innervated by the ascending monoaminergic (noradrenergic, dopaminergic, serotonergic) and cholinergic systems.

Pyramidal cells, which represent the major neuronal population of the cerebral cortex, are the output neurons that integrate and transfer information from extra-cortical inputs and local circuits to distant cortical areas and sub-cortical structures. Several electrophysiological classes of pyramidal neurons have been characterized, mainly on the basis of their response to application of prolonged intracellular current pulses as well as the shape of their action potentials (Connors and Gutnick, 1990). These electrophysiological properties have been mostly analysed from in vitro studies performed on the rat and guinea pig cerebral cortex. Two main classes of pyramidal neurons have been described: the regular spiking (RS) and the intrinsic bursting (IB) cells (Connors et al., 1982; Stafstrom et al., 1984; McCormick et al., 1985; Chagnac-Amitai et al., 1990; Mason and Larkman, 1990; Van Brederode and Snyder, 1992; Kang and Kayano, 1994). The in vivo electrophysiological characteristics of pyramidal cells have only been described in a few reports. In addition to RS and IB cells, two additional classes of pyramidal cells were revealed in these in vivo studies: the fast-adapting RS cells and the non-inactivating bursting cells (NIB), which were found in the cat associative and motor cortex, respectively (Baranyi et al., 1993a; Nuñez et al., 1993).

The electrophysiological characteristics of PFC pyramidal cells have been analysed in a few in vitro studies that have also revealed the presence of RS and IB pyramidal cells (de la Peña and Geijo-Barrientos, 1996; Yang et al., 1996). However, the in vivo electrophysiological properties of PFC pyramidal cells still remain to be determined. Therefore, the present study was undertaken to investigate the basic electrophysiological features of pyramidal cells of the rat PFC, using both in vivo intracellular recording and staining. No attempt was made to investigate local inhibitory interneurons.

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