NMDA receptors in the insular cortex modulate cardiovascular and autonomic but not neuroendocrine responses to restraint stress in rats

Abstract

Background and Purpose: The insular cortex (IC) is a brain structure involved in the modulation of autonomic, cardiovascular and neuroendocrine adjustments during stress situations. However, the local neurochemical mechanisms involved in the control of these responses by the IC are poorly understood. Glutamate is a prominent excitatory neurotransmitter in the brain. Thus, the current study aimed to investigate the involvement of glutamatergic neurotransmission within the IC in cardiovascular, autonomic and neuroendocrine responses to acute restraint stress. Experimental Approach: The selective NMDA glutamate receptor antagonist LY235959 (1 nmol/100 nL) and the selective non-NMDA glutamate receptor antagonist NBQX (1 nmol/100 nL) were microinjected into the IC 10 min before the onset of restraint stress. Key Results: The antagonism of NMDA receptors within the IC potentiated the restraint-evoked increases in both arterial pressure and heart rate, while non-NMDA blockade had no effect on these parameters. Spontaneous baroreflex analysis demonstrated that microinjection of LY235959 into the IC decreased baroreflex activity during restraint stress. The decrease in tail skin temperature during restraint stress was shifted to an increase in animals treated with the NMDA receptor antagonist. Moreover, the blockade of IC glutamate receptors did not affect the increase in circulating corticosterone levels during restraint stress. Conclusion and Implications: Overall, our findings provide evidence that IC glutamatergic signalling, acting via NMDA receptors, plays a prominent role in the control of autonomic and cardiovascular responses to restraint stress but does not affect neuroendocrine adjustments.

Stress-altering anterior insular cortex activity affects risk decision-making behavior in mice of different sexes

“…prominent role in the restraint stress of rats (Goulart et al, 2022). Moreover, insula activation has been implicated in negative emotions in many imaging studies of humans (Namkung et al, 2017).…”