Synaptic Influence of Hippocampus on Pyramidal Cells of the Rat Prefrontal Cortex: An In Vivo Intracellular Recording Study

Abstract

The hippocampus and prefrontal cortex are two structures implicated in learning and memory and are related through a direct excitatory pathway. The characteristics of the synaptic influence of the hippocampus on pyramidal cells of the prefrontal cortex were determined using intracellular recordings in anesthetized rats. Single-pulse stimulation of the hippocampus induced an early EPSP of fixed latency in most of the recorded pyramidal cells (n = 106/116) thereby demonstrating a monosynaptic connection between hippocampal neurons and pyramidal cells of the prefrontal cortex. Furthermore, the EPSP was followed by a prolonged IPSP and suggests a simultaneous engagement of pyramidal and non-pyramidal neurons that may ultimately constrain the spread of excitation in response to hippocampal input. Paired-pulse stimulation induced short-term modifications in the synaptic responses and this short-term plasticity may contribute to the temporal filtering of information. Finally, tetanic stimulation of the hippocampus produced long-term potentiation of the monosynaptic EPSP with a concomitant potentiation of the IPSP, indicating that the hippocampo-prefrontal network can participate in the formation and consolidation of memories. In conclusion, the characteristics of the synaptic transmission in the hippocampo-prefrontal cortex pathway further supports the existence of a cooperative relationship between two structures known to be involved in higher cognitive processes.

Age-related changes in nitric oxide activity, cyclic GMP, and TBARS levels in platelets and erythrocytes reflect the oxidative status in central nervous system

“…Experimental data suggest that the hippocampal-prefrontal network can participate in the formation and consolidation of memories (Laroche et al 1990;Dégenètais et al 2003). Therefore, the similar changes observed in NOS activity and TBARS/cyclic GMP levels and the characteristics of the excitatory synaptic transmission in the hippocampal-prefrontal cortex pathway further supports the existence of a cooperative relationship between two structures known to be involved in higher cognitive processes.…”

Effects of early life permethrin exposure on spatial working memory and on monoamine levels in different brain areas of pre-senescent rats

“…Hippocampal activity is important for a configuration of an allocentric map (Olvera-Cortés et al, 2002Poucet, 1993) that can then be translated into effective working memory performance in the PFC (Dégenètais et al, 2003] by virtue of the direct Hip-PFC connections (Cenquizca and Swanson, 2007). Whereas, for egocentric processing, connectivity between the Str and the mPFC appears to play a primary role (McDonald and White, 1994;Postle and D'Esposito, 2003).…”

Clozapine and Haloperidol Differently Suppress the MK-801-Increased Glutamatergic and Serotonergic Transmission in the Medial Prefrontal Cortex of the Rat

“…What is the actual localization of these NMDA receptors and the source of the cortical hyperglutamatergic transmission induced by their blockade? Two of the well-known ascending glutamatergic inputs to the mPFC arise from the hippocampus (Carr and Sesack, 1996;Dégenètais et al, 2003) and the mediodorsal nucleus of the thalamus (Kuroda et al, 1998), and in both areas glutamatergic neurons are under the control of GABAergic cells (Gigg et al, 1994; Number of animals is given in parentheses. The control group received two injections (saline and vehicle) and, for the sake of clarity, is depicted as a dotted line.…”