Article
Does cable-bound stimulation and recording of neuronal activity affect rats’ wellbeing?
Beeinflusst die kabelgebundene Stimulation und Aufzeichnung der neuronalen Aktivität das Wohlbefinden der Ratte?
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Published: | June 4, 2021 |
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Objective: Chronic stimulation and recording of neuronal activity in different rodent models for movement disorders and neuropsychiatric disturbances is carried out via a cable with a swivel that allows relative free movement of the rat without twisting of the cable. Nevertheless, it is still semi-restraining and may therefore impose stress and confound to the animal.
We here subcutaneously implanted transmitters for contactless recording of heart rate and activity of rats during cable-bound stimulation and recording of neuronal activity, which was compared to the perioperative period of intracranial electrode implantation.
Methods: Male Sprague Dawley rats (n=8, 180 g) were implanted with electrodes in the subthalamic nucleus (STN) under general anesthesia with local anesthesia and perioperative pain management with non-steroidal anti-inflammatory drugs. Two weeks after electrode implantation the threshold for stimulation-induced side effects was determined in each rat. Thereafter, a five-day sham-stimulation period started with only the cable connected to the rat’s electrode head stage but no current applied. Finally, the cables were disconnected and rats were allowed to move freely in their cages for another two days. In addition to continuous monitoring of heart rate and activity via a subcutaneously implanted transmitter, the rats’ well-being and general health condition were monitored by daily body weight measures and clinical scoring.
Results: Clinical scoring and weight measures during the course of the study did not show any substantial alterations. Right after electrode implantation, heart rate was elevated, however, without reaching the level of significance. Only the first two days of cable-bound sham-stimulation resulted in decreased locomotor activity (p<0.05) as compared to pre- and post-stimulation values, whereas heart rate measures were not affected.
Conclusion: Electrode implantation and semi-restraint caused by tethered electrodes had only a transient and mild effect on rat’s activity. Since so far even advanced and fully implantable devices do not allow flexible switching between recording and electric stimulation with different settings, as e.g., needed for adaptive “closed loop” stimulation, our stimulation/recording setup may be valid and ethically justifiable in neuroscience rat models.