Cuneiform nucleus and Dorsomedial Hypothalamic nucleus and Perifornical area in the control of laryngeal activity and subglottic pressure in spontaneously breathing anaesthetized rats.

Abstract

Background: The DMH-PeF and the CnF have been involved in sympathetic activity due their connectivity with several nuclei involved in cardiorespiratory control. In previous studies we have demonstrated a functional interaction between hypothalamic and mesencephalic structures with several rostral and ventral pontine structures that are involved in the changes of laryngeal caliber. The aim is to characterize the role of the DMH-PeF and CnF in modulating laryngeal activity and their effects on vocalization.

Experimental studies were carried out with male Sprague-Dawley rats (n=42) (250-300g). Animals were anesthetized with sodium pentobarbitone (60 mg/kg i.p., initial dose, supplemented 2 mg/kg, i.v.). Electrical stimulations (n=14) using concentric bipolar electrodes (1ms pulses, 20-40μA, 100Hz for 5s) microinjections of PBS-Evans Blue (250nl, pH 7.4±0.1, 5-s duration) (n=14) or glutamate (0,25M, 250nl) (n=14) were performed. Respiratory flow, pleural pressure, subglottic pressure, blood pressure and heart rate were also recorded.

DMH-PeF and CnF PBS-Evans Blue microinjections did not produce any significant changes in any of the cardiorespiratory variables recorded. However, electrical stimulations in both regions evoked a decrease of laryngeal resistance (subglottal pressure) (p<0,001). Glutamate microinjections within the DMH-PeF and CnF evoked a decrease of laryngeal resistance (p<0,01 and p<0,001 respectively) accompanied with an inspiratory facilitatory response consisted of an increase in respiratory rate (p<0,001 in both cases), together with a pressor (p<0,001 and p<0,01 respectively) and tachycardic response (p<0,001in both cases).

Conclusions The results of our study contribute with new data on the role of the hypothalamic-mesencephalic neuronal circuits in the control mechanisms of subglottic pressure and laryngeal activity.