Barotransmitters: The Neglected Class of Transmitters

4 March 2009

Sadollah Mohammadi

Pressure is defined as a perpendicular load or force on a surface, and the bar is a widely used metric unit of measure for pressure. It is a fundamental parameter in thermodynamics. To maintain a homeostatic internal environment, pressure control must be a highly regulated process in complex systems such as the human body. Fluid pressures in different parts of the body, especially in cardiovascular, cerebral and ocular systems, are carefully regulated, indicating the crucial roles of pressure receptors in maintaining whole-body homeostasis (1).

The pressure regulation process involves the release of specific transmitter molecules following the activation of specific signaling pathways. The production of natriuretic peptides, nitric oxide, glutamate, substance P, and acetylcholine have been reported to change in response to pressure fluctuation (2, 3, 4, 5). These transmitters comprise heterogeneous molecules in terms of their structure. However, all of them are controlled by the level of pressure and mediate transference of the signals of pressure changes to target cells or organs.

The classification of transmitters is based on a number of criteria (6). One of the simplest is the type of stimulus that triggers the release of the transmitter. To emphasize the close relationship between transmitters released in response to pressure and pressure receptors, we propose the term "barotransmitter" for this class of molecules to denotes the similarity in transmitters that are endogenously released in response to a change in pressure. The term "barotransmitter" as a descriptive category for transmitters for pressure receptors could be used describe and integrate the ways that pressure affects biological functions.

References

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3. N. Singewald, A. Philippu, Involvement of biogenic amines and amino acids in the central regulation of cardiovascular homeostasis. Trends Pharmacol. Sci. 17, 356-363 (1996).
4. J. R. Gontijo, L. A. Smith, U. C. Kopp, CGRP activates renal pelvic substance P receptors by retarding substance P metabolism. Hypertension 33493- 498 (1999).
5. H. Schworer, K. Racke, H. Kilbinger, Characterization of the muscarine receptors involved in the modulation of serotonin release from the vascularly perfused small intestine of guinea pig. Naunyn Schmiedebergs Arch. Pharmacol. 339, 263-267 (1989).
6. D. Hoyer, P. P. Humphrey, Nomenclature and classification of transmitter receptors: An integrated approach. J. Recept. Signal Transduct. Res. 17, 551-568 (1997).

This response contributed by Sadollah Mohammadi and Masoud Darabi