Low frequency pulse stimulation of Schaffer collaterals in Trpm4-/- knockout rats differently affects baseline BOLD signals in target regions of the right hippocampus but not BOLD responses at the site of stimulation.
Electrical stimulation of right Schaffer collateral in Trpm4-/- knockout and wild type rats were used to study the role of Trpm4 channels for signal processing in the hippocampal formation. Stimulation induced neuronal activity was simultaneously monitored in the CA1 region by in vivo extracellular field recordings and in the entire brain by BOLD fMRI measurements. In wild type and Trpm4-/- knockout rats, consecutive 5 Hz pulse trains elicited similar neuronal responses in the CA1 region and similar BOLD responses in the stimulated right hippocampus. Stimulus-related positive BOLD responses were also found in the left dorsal hippocampus. In contrast to the right dorsal hippocampus, baseline BOLD signals in the left hippocampus significantly decreased during consecutive stimulation trains. Similarly, slowly developing significant declines in baseline BOLD signals, in absence of any positive BOLD responses, were also observed in the right entorhinal, right piriform cortex, right basolateral amygdala and right dorsal striatum whereas baseline BOLD signals remained almost stable in the corresponding left regions. Furthermore, significant declines in baseline BOLD signals were found in the prefrontal cortex and prelimbic/infralimbic cortex. Because significant baseline BOLD declines were only observed in target regions of the right dorsal hippocampus, it might reflect functional connectivity between these regions. In all observed regions the decline in baseline BOLD signals was significantly delayed and less pronounced in Trpm4-/- knockout rats when compared to wild type rats. Thus, either Trpm4 channels are involved in mediating these baseline BOLD shifts or functional connectivity of the hippocampus is impaired in Trpm4-/- knockout rats.
['Bovet-Carmona|Marta|M|', 'Krautwald|Karla|K|', 'Menigoz|Aurélie|A|', 'Vennekens|Rudi|R|', 'Balschun|Detlef|D|', 'Angenstein|Frank|F|']
D000818:Animals D056547:CA1 Region, Hippocampal D004558:Electric Stimulation D000069280:Electrocorticography D005260:Female D007839:Functional Laterality D006624:Hippocampus D008279:Magnetic Resonance Imaging D008297:Male D051381:Rats D055647:Rats, Transgenic D050053:TRPM Cation Channels
BOLD TRPM4 CA1 fMRI In vivo electrophysiology