Cardiovascular effects of the microinjection of L-proline into the third ventricle or the paraventricular nucleus of the hypothalamus in unanesthetized rats.

Abstract

We investigated the cardiovascular effects of the microinjection of L-proline (L-Pro) into the third ventricle (3V) and its peripheral mechanisms. Different doses of L-Pro into the 3V caused dose-related pressor and bradycardiac responses. The pressor response to L-Pro injected into the 3V was potentiated by intravenous pretreatment with the ganglion blocker pentolinium (5 mg/kg), thus excluding any significant involvement of the sympathetic nervous system. Because the response to the microinjection of L-Pro into the 3V was blocked by intravenous pretreatment with the V1-vasopressin receptor antagonist dTyr(CH(2) )(5) (Me)AVP (50μg/kg), it is suggested that these cardiovascular responses are mediated by a vasopressin release. The pressor response to the microinjection of L-Pro into the 3V was found to be mediated by circulating vasopressin, so, given that the paraventricular nucleus of the hypothalamus (PVN) is readily accessible from the 3V, we investigated whether the PVN could be a site of action for the L-Pro microinjected in the 3V. The microinjection of L-Pro (0.033 μmoles/0.1 μl) into the PVN caused cardiovascular responses similar to those of injection of the 3V and were also shown to be mediated by vasopressin release. In conclusion, these results show that the microinjection of L-Pro into the 3V causes pressor and bradycardiac responses that could involve stimulation of the magnocellular cells of the PVN and release of vasopressin into the systemic circulation. Also, because the microinjection of L-Pro into the PVN caused a pressor response, this is the first evidence of cardiovascular effects caused by its injection in a supramedullary structure.

• Authors: Silvana Lopes-Azevedo, América Augusto Scopinho, Cristiane Busnardo, Fernando Morgan Aguiar Corrêa
• Journal: Journal of neuroscience research (J Neurosci Res) Vol. 90 Issue 11 Pg. 2183-92 (Nov 2012) ISSN: 1097-4547 [Electronic] United States
• PMID: 22740501 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Wiley Periodicals, Inc.

Chemical References

• Proline

Topics

• Animals
• Blood Pressure (drug effects)
• Cardiovascular System (drug effects)
• Dose-Response Relationship, Drug
• Heart Rate (drug effects)
• Male
• Microinjections
• Paraventricular Hypothalamic Nucleus (drug effects)
• Proline (administration & dosage)
• Rats
• Rats, Wistar
• Third Ventricle (drug effects)