Abstract
Objective: Our objective was to investigate the cardiovascular effects of the chemical stimulation of the PVN with L‐glutamate (L‐glu) as well as the central and peripheral mechanisms involved. Methods: Male Wistar rats were used. Guide cannulas were implanted in the PVN. A catheter was introduced into the right femoral artery for blood pressure and heart rate recording. Results: Microinjection of L‐glu in 100 nL into the PVN caused dose‐related pressor and tachycardiac responses in unanesthetized rats, with an ED50 of approximately 10nmol. The cardiovascular response to L‐glu into the PVN was blocked by intravenous pretreatment with the ganglion blocker pentolinium, suggesting that this response is mediated by an increase in sympathetic activity. The response to L‐glu was not affected by local microinjection of the selective non‐NMDA receptor antagonist NBQX (2 nmol). The pressor response was not affected, but the tachycardia was converted into bradycardia by local pretreatment with the selective NMDA receptor antagonist LY235959 (2 nmol), indicating the involvement of NMDA receptors in these responses. Conclusion: The results suggest that injection of L‐glu into the PVN activates the sympathetic output and that the tachycardiac response to the injection of L‐glu into the PVN is mediated by NMDA receptors. Financial Support: FAPESP (06/52446‐9).
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