Heart Rate Variability (HRV) in Frequency‐domain estimate the distribution into low‐frequency (LF: 0.04–0.15 Hz) and high‐frequency (HF 0.15–0.4 Hz) bands. On the other hand, when analyzing norepinephrine and acetylcholine cell signalling time kinetics, the summation of such times once converted to frequencies in Hertz, match the previously mentioned LF and HF values.Materials and MethodsGoogle Scholar databases and National Library of Medicine, were searched for articles published from 2000 to 2019 related to the time kinetics involved in cell signaling, with the following combination of terms: 1) “Title (TI) = (FRET) AND TI = (BRET) OR ‘Activation time B1 adrenergic’ OR ‘Activation time M2 muscarinic’ OR ‘Gs Protein Activation’ OR ‘Gi Protein Activation’ ‘Time Kinetics’ OR ‘Adenylate Cyclase’ ‘Activation HCN4’ OR ‘Nodal Pace Marker’ OR ‘In Vitro Model Cells')]”. The inclusion criteria for each study included the ligand‐receptor interaction and time related signalling cascade involved in the depolarization or hyperpolarization of cells. Both database searches yielded 7 studies matching the inclusion criteria. Once all the times of cell signalling cascade were found or estimated for all receptors, such times were summed, they were converted to Hertz using the inverse relationship between time and frequency.RESULTSDatabase searches yielded 7 studies matching the inclusion criteria. For B1‐Adrenergic Receptor cell signalling cascade the estimated times were: Ligand‐Receptor‐Activation (0.045 s), Receptor Gs protein interaction (0.044 s), Gs protein activation (0.369 s), Adenylate Cyclase activation (28.8s), cAMP mediated activation of HCN4 (0.461 s), for a total of 29.76 seconds, yielding 0.0336 Hz.For M2‐Cholinergic Receptor the estimated times were: Ligand‐Receptor activation (0.750 s), Receptor Gi protein interaction (12 ns**), Gi protein activation (1 s), and Gi mediated Adenylate Cyclase inactivation (3 s), for a total of 4.75 seconds, yielding 0.211 Hz.DISCUSSIONB1‐Adrenergic Receptor cell signaling summed 29.76 seconds, yielding 0.0336 Hertz, a very close value to the 0.04 Hz of LF band. On the other hand, M2 Cholinergic receptor cell signalling time was 4.75 s, yielding 0.211 Hz, a value within the HF band range of 0.15 to 0.4 Hz. Such results coincide with the possibility of direct correlation of biochemical cell signalling and HF and LF bands spectrums. However due to the scarcity of biochemical studies, it is important to mention that during the estimation process there was two issues worth mentioning. First, B1 Adrenergic Receptor Gs Adenylate cyclase activation was roughly estimated. Second, for M2 Cholinergic Gi mediated AC inhibition, a A2‐Adrenergic receptor model was used. Despite the previously mentioned limitations, the current study results suggest the possibility that LF and HF band spectrum could be refined into smaller range of Hertz segments, which might correspond to the summation of time kinetics involved in cell signalling cascade related to the different adrenergic or cholinergic receptor subtypes.Support or Funding InformationPROSEIMThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Introduction “In vivo” electromyography usually reports a frequency domain muscle activity in a broad Hertz spectrum that ranges from 1 Hz to 500 Hz. However, when the contiguous nicotinic biochemical events in rhabdomyocytes type Ia, IIa and IIb are timed “in vitro”, and then converted to Hertz. A reduced electromyographic frequency domain is obtained. Materials and Methods Google Scholar databases and National Library of Medicine, were searched for articles published from 1990 to 2019 containing times of kynetic cell signalig in raddomiocytes type Ia IIa and IIB join terms like 1) “Title (TI)= ‘Time Acetylcholine exocytosis’ AND ‘Time Activation nicotinic receptor’ AND ‘Time Depolarization of sarcolemma’ AND ‘Excitation–contraction coupling’ AND ‘Time depolarization T‐tubule” AND ‘Cross‐bridge cycle’. The inclusion criteria were that each study involving a types of striated muscle fiber “In vitro” as an objective measure interaction Acetylcholine‐Nicotinic Recepptor and cascade cell signaling to evaluating speed of despolarizatig and every physiological contraction subphases of contraction. Once every time of physiological event of contraction was found, the time was added and then the mathematical inverse of the period in seconds was converted to frequency in Hertz. Results “In vitro” the total time events of contraction summed to striated muscle fiber Type IA were 3,33 ms; Fibers Type IIA were 6,81 ms; and Fibers Type IIB were 7,41 ms. Times that converted to Hertz show fiber type Ia, IIa IIb with 3,03 Hz, 1,46 Hz, 1,34 Hz Conclusions The electromiographic Hertz domain is made of a series of “noise” such as the different extracellular events that occur between inferior motor neurons and sarcolemmas. The present work aims to rationalize the obtained “in vitro” frequency spectrum values of 3,03 Hz, 1,46 Hz, 1,34 Hz for type Ia, IIa and IIb respectively. Support or Funding Information UNIVERSIDAD DE LA SABANA