Basal Synaptic Transmission and Long-Term Plasticity at CA3-CA1 Synapses Are Unaffected in Young Adult PINK1-Deficient Rats

Abstract

Loss of function mutations in PARK6, the gene that encodes the protein PTEN-induced kinase 1 (PINK1), cause autosomal recessive familial Parkinson’s disease (PD). While PD is clinically diagnosed by its motor symptoms, recent studies point to the impact of non-motor symptoms, including cognitive dysfunction in the early pre-motor stages of the disease (Aarsland et al., 2004; Chaudhuri and Schapira, 2009). As the hippocampus is a key structure for learning and memory, this study aimed to determine whether synaptic transmission is affected at CA3-CA1 excitatory synapses in PINK1 knockout rats at an age when we recently reported a gain of function at excitatory synapses onto spiny projection neurons in the dorsal striatum (Creed et al., 2020) and when motor symptoms are beginning to appear (Dave et al., 2014). Using extracellular dendritic field excitatory postsynaptic potential recordings at CA3-CA1 synapses in dorsal hippocampus 4-to 5- month old PINK1 KO rats and wild-type littermate controls, we observed no detectable differences in the strength of basal synaptic transmission, paired-pulse facilitation, or long-term potentiation. Our results suggest that loss of PINK1 protein does not cause a general dysfunction of excitatory transmission throughout the brain at this young adult age when excitatory transmission is abnormal in the striatum.

PINK1 knockout rats show premotor cognitive deficits measured through a complex maze

“…A study using resting-state functional MRI identified reduced connectivity between the neostriatum, midbrain dopaminergic regions, hypothalamus, and thalamus and increased connectivity between the ventral midbrain dopaminergic regions and hippocampus in 6–8-month-old PINK1 −/− rats compared to WT ( Ferris et al, 2018 ; Cai et al, 2019 ). Still, a study measuring hippocampal synaptic plasticity between 4 and 5 months old found no impairment in PINK1 −/− rats compared to controls ( Memon et al, 2021 ). Our study in this PD rat model showed elevated levels of both norepinephrine (NE) and DA in the PFC at a younger age, suggesting the possibility of abnormal DA or NE signaling therein ( Soto et al, 2024 ).…”