Strain, M. M. | Search bioRxiv

bioRxiv2026

Treadmill Stepping in Newborn Rats

The purpose of this study was to investigate the influence of treadmill belt speed on mechanically-induced (tail-pinch) and pharmacologically-induced (quipazine, a 5HT2A agonist) stepping behavior in one-day old rats. On postnatal day 1 (P1), male rat pups were tested on one of four moving treadmill belt speeds. Stepping was induced using a tail-pinch and quipazine administration to examine real-time adaptations on belt speeds. For tail-pinch-induced stepping in the forelimbs and hindlimbs, there was a significant effect of time but not belt speed. Step cycle duration was significantly shorter for both forelimbs and hindlimbs on the fast belt speed compared to all other belt speeds. For the forelimbs, this effect was driven by changes in stance phase duration. Compared to control the speed, step area was significantly larger on medium and fast speeds for forelimbs and slow and fast speeds for hindlimbs. For quipazine-induced stepping, forelimbs and hindlimbs showed significantly more steps across slow, medium, and fast belt speeds compared to the control speed. The forelimbs showed significantly shorter step cycle durations on the fast belt speed compared to the control belt speed. Again, this difference was driven by changes in the stance phase. There were no significant differences in step cycle duration, stance and swing phase durations, or step area between speeds for the hindlimbs. Overall, we showed that both mechanical and pharmacological stimulation is reliable at inducing stepping on a moving treadmill belt in neonatal rats, and P1 rats show real-time adaptations in response to a moving treadmill belt.

neuroscience↗

bioRxiv2023

Dorsal Motor Vagal Neurons Can Elicit Bradycardia and Reduce Anxiety-Like Behavior

Cardiovagal neurons (CVNs) innervate cardiac ganglia through the vagus nerve to control cardiac function. Although the cardioinhibitory role of CVNs in nucleus ambiguus (CVNNA) is well established, the nature and functionality of CVNs in dorsal motor nucleus of the vagus (CVNDMV) is less clear. We therefore aimed to characterize CVNDMV anatomically, physiologically, and functionally. Optogenetically activating cholinergic DMV neurons resulted in robust bradycardia through peripheral muscarinic (parasympathetic) and nicotinic (ganglionic) acetylcholine receptors, but not beta-1-adrenergic (sympathetic) receptors. Retrograde tracing from the cardiac fat pad labeled CVNNA and CVNDMV through the vagus nerve. Using whole cell patch clamp, CVNDMV demonstrated greater hyperexcitability and spontaneous action potential firing ex vivo despite similar resting membrane potentials, compared to CVNNA. Chemogenetically activating DMV also caused significant bradycardia with a correlated reduction in anxiety-like behavior. Thus, DMV contains uniquely hyperexcitable CVNs capable of cardioinhibition and robust anxiolysis.

neuroscience↗