There are powerful pathways descending from the auditory cortex (AC) to the inferior colliculus (IC), yet their function is not fully understood. The aim of this study is to examine the effects of a reversible cortical inactivation, achieved by cooling of the AC, on the responses of neurons in the rat IC. Extracellular single-unit or multi-unit activity was recorded in the IC of anaesthetized rats with a 16-channel multielectrode probe introduced along the IC dorso-ventral axis through the dorsal cortex (DCIC) to the central nucleus of the IC (CIC). Cooling of the AC produced an increase in spontaneous activity and magnitude of the sound-evoked response in 47% of the IC neurons. Maximal changes in the neuronal activity were observed in the DCIC and the central part of the CIC. The final segments of the sustained responses to 60 ms stimuli and the off responses were more affected than the onset segments. Inactivation of the AC resulted in a suppression of the post-excitatory inhibition and neuronal adaptation, which was reflected in a pronounced enhancement of synchronized responses to a series of fast repeated clicks. The response parameters recovered, at least partly, to the pre-cooling levels 1 h after the cooling cessation. The frequency tuning properties of the IC neurons did not show any significant changes during the cooling period. The results demonstrate that AC cooling inactivates excitatory corticofugal pathways and results in a less activated intrinsic inhibitory network in the IC.
- MeSH
- akustická stimulace MeSH
- časové faktory MeSH
- colliculus inferior metabolismus patologie patofyziologie MeSH
- fyziologická adaptace MeSH
- GABAergní neurony metabolismus MeSH
- nervový útlum MeSH
- potkani Long-Evans MeSH
- sluchová dráha patofyziologie MeSH
- sluchové evokované potenciály MeSH
- sluchové korové centrum metabolismus patologie patofyziologie MeSH
- terapeutická hypotermie * MeSH
- termoregulace * MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
For all sensory organs, the establishment of spatial and temporal cortical resolution is assumed to be initiated by the first sensory experience and a BDNF-dependent increase in intracortical inhibition. To address the potential of cortical BDNF for sound processing, we used mice with a conditional deletion of BDNF in which Cre expression was under the control of the Pax2 or TrkC promoter. BDNF deletion profiles between these mice differ in the organ of Corti (BDNF (Pax2) -KO) versus the auditory cortex and hippocampus (BDNF (TrkC) -KO). We demonstrate that BDNF (Pax2) -KO but not BDNF (TrkC) -KO mice exhibit reduced sound-evoked suprathreshold ABR waves at the level of the auditory nerve (wave I) and inferior colliculus (IC) (wave IV), indicating that BDNF in lower brain regions but not in the auditory cortex improves sound sensitivity during hearing onset. Extracellular recording of IC neurons of BDNF (Pax2) mutant mice revealed that the reduced sensitivity of auditory fibers in these mice went hand in hand with elevated thresholds, reduced dynamic range, prolonged latency, and increased inhibitory strength in IC neurons. Reduced parvalbumin-positive contacts were found in the ascending auditory circuit, including the auditory cortex and hippocampus of BDNF (Pax2) -KO, but not of BDNF (TrkC) -KO mice. Also, BDNF (Pax2) -WT but not BDNF (Pax2) -KO mice did lose basal inhibitory strength in IC neurons after acoustic trauma. These findings suggest that BDNF in the lower parts of the auditory system drives auditory fidelity along the entire ascending pathway up to the cortex by increasing inhibitory strength in behaviorally relevant frequency regions. Fidelity and inhibitory strength can be lost following auditory nerve injury leading to diminished sensory outcome and increased central noise.
- MeSH
- colliculus inferior patologie patofyziologie MeSH
- delece genu MeSH
- hluk * MeSH
- integrasy metabolismus MeSH
- kochlea metabolismus MeSH
- mozkový neurotrofický faktor metabolismus MeSH
- myši knockoutované MeSH
- promotorové oblasti (genetika) genetika MeSH
- receptor trkC metabolismus MeSH
- rizikové faktory MeSH
- sluch MeSH
- sluchové kmenové evokované potenciály MeSH
- sluchové korové centrum metabolismus patologie patofyziologie MeSH
- sluchový práh MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- akustická stimulace * metody MeSH
- colliculus inferior * anatomie a histologie fyziologie patofyziologie MeSH
- elektrická stimulace metody přístrojové vybavení MeSH
- epilepsie reflexní * etiologie klasifikace patofyziologie MeSH
- experimenty na zvířatech MeSH
- krysa rodu rattus MeSH
- mozková kůra anatomie a histologie patofyziologie MeSH
- náchylnost k nemoci MeSH
- poranění mozku etiologie patofyziologie MeSH
- příznaky a symptomy MeSH
- statistika jako téma MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
