The Importance of Ventral Hippocampal Dopamine and Norepinephrine in Recognition Memory

Abstract

Dopaminergic neurons originating from the ventral tegmental area (VTA) and the locus coeruleus are innervating the ventral hippocampus and are thought to play an essential role for efficient cognitive function. Moreover, these VTA projections are hypothesized to be part of a functional loop, in which dopamine regulates memory storage. It is hypothesized that when a novel stimulus is encountered and recognized as novel, increased dopamine activity in the hippocampus induces long-term potentiation and long-term storage of memories. We here demonstrate the importance of increased release of dopamine and norepinephrinein the rat ventral hippocampus on recognition memory, using microdialysis combined to a modified novel object recognition test. We found that presenting rats to a novel object significantly increased dopamine and norepinephrine output in the ventral hippocampus. Two hours after introducing the first object, a second object (either novel or familiar) was placed in the same position as the first object. Presenting the animals to a second novel object significantly increased dopamine and norepinephrine release in the ventral hippocampus, compared to a familiar object. In conclusion, this study suggests that dopamine and norepinephrine output in the ventral hippocampus has a crucial role in recognition memory and signals novelty.

A Novel and Selective Dopamine Transporter Inhibitor, (S)-MK-26, Promotes Hippocampal Synaptic Plasticity and Restores Effort-Related Motivational Dysfunctions

“…Evoked fEPSPs were recorded at the CA1 stratum-radiatum layer after electrically stimulating the collateral projections of Schaffer coming from the CA3 region as previously reported [ 56 , 185 ]. For the recordings, the hippocampi were divided into four major sections along the septo-temporal axis, taking its anatomical transversal middle as the absolute center, and slices within the approximately 30–40% section from the nominal center towards the ventral region (longitudinally) were selected for recordings; a region that has been previously showing to display robust LTP responses [ 186 , 187 ] and that receives inputs from dopaminergic neurons projecting from the locus coeruleous and ventral tegmental areas [ 188 ]. Recording pipettes were pulled with a P-87 horizontal puller (Sutter Instrument, Novato, CA) and filled with aCSF (series resistances were of 3 ± 1 MΩ).…”

Particulate matter constituents trigger the formation of extracellular amyloid β and Tau-containing plaques and neurite shorteningin vitro

“…We employed a human neuroblastoma cell line called SH-SY5Y, which is extensively u�lized in studies due to their ability to differen�ate into neuron-like cells. When differen�ated, these cells exhibit characteris�cs resembling dopaminergic neurons found in the ventral hippocampus, which are involved in cogni�ve func�ons (Titulaer et al, 2021). A�er differen�a�on of SH-SY5Y, resul�ng in neuron-like cells with extensively branched neurites (Figure 1 A green) (Agholme et al, 2010;Kovalevich et al, 2021;Kovalevich & Langford, 2013), we exposed them to TiO2 nanotubes (Figure 1 A red).…”

An Artificial Autonomic Nervous System That Implements Heart and Pupil as Controlled by Artificial Sympathetic and Parasympathetic Nerves

“…NA output in the ventral hippocampus has a crucial function in recognition memory. [50,51] The "Little Albert" experiment [52] was simulated by applying white rat (−3.5 V) and hammer (−4 V) stimulation to the PCST (Figure 4d). The threshold of EPSC was broken in a short space of time.…”