Involvement of non-NMDA glutamate receptors of the hypothalamic paraventricular nucleus in the cardiovascular response to the microinjection of noradrenaline into the dorsal periaqueductal gray area of rats

• NA microinjection into the dPAG evoked pressor and bradycardiac responses.
• PVN is a relay of the dPAG noradrenergic pressor pathway.
• Non-NMDA glutamate receptors antagonist in the PVN blocked pressor response to NA.
• Glutamatergic neurotransmission within PVN mediates cardiovascular response to NA.

The dorsal periaqueductal gray area (dPAG) is involved in cardiovascular modulation. In a previous study, we showed that noradrenaline (NA) microinjected into the dPAG caused a vasopressin-mediated pressor response, involving a relay in the hypothalamic paraventricular nucleus (PVN). In the present study, we evaluated the involvement of ionotropic glutamate receptors within the PVN in the cardiovascular response to NA microinjection into the dPAG of unanesthetized rats. Microinjection of the selective NMDA glutamate receptor antagonist LY235959 (2 nmol/100 nL) unilaterally into the PVN did not affect the cardiovascular response evoked by microinjection of NA (15 nmol/50 nL) into the dPAG. On the other hand, unilateral PVN pretreatment with the non-NMDA glutamate receptor antagonist NBQX (2 nmol/100 nL) significantly reduced the pressor and cardiac response caused by microinjection of NA into the dPAG. In addition, bilateral PVN pretreatment with NBQX (2 nmol/100 nL) blocked the cardiovascular response to NA injected into the dPAG. In conclusion, the present results suggest that bilateral PVN activation of non-NMDA glutamate receptors mediates the vasopressin-related cardiovascular response to the microinjection of NA into the dPAG.