Effects of disinhibition of neurons in the dorsomedial hypothalamus on central respiratory drive

Lachlan M. McDowall, Jouji Horiuchi, Roger A. L. Dampney
2007 American Journal of Physiology. Regulatory Integrative and Comparative Physiology  
McDowall LM, Horiuchi J, Dampney RA. Effects of disinhibition of neurons in the dorsomedial hypothalamus on central respiratory drive. Neurons within the dorsomedial hypothalamus (DMH) play a critical role in subserving the cardiovascular and neuroendocrine response to psychological stress. An increase in respiratory activity is also a characteristic feature of the physiological response to psychological stress, but there have been few studies of the role of DMH neurons in regulating
more » ... gulating respiratory activity. In this study we determined the effects of activation of DMH neurons on respiratory activity (assessed by measuring phrenic nerve activity, PNA) and the relationship between evoked changes in respiratory activity and changes in sympathetic vasomotor activity in spontaneously breathing urethane-anesthetized rats. Microinjections of bicuculline (4 -40 pmol in 20 nl) into the DMH evoked dose-dependent increases in PNA burst frequency and amplitude. These were accompanied by dose-dependent decreases in mean tracheal CO2 levels, indicative of hyperventilation. In control experiments, microinjections of bicuculline into sites adjacent to the DMH evoked much smaller or no changes in PNA. In experiments where renal sympathetic nerve activity (RSNA) was also measured, cycle-triggered averaging revealed that RSNA under resting conditions was partly correlated with the PNA, but in response to DMH disinhibition there was no consistent change in the amplitude of the respiratory-related variations in RSNA. The results indicate that DMH neurons can exert a powerful stimulatory effect on respiratory activity, causing hyperventilation. This is not associated with an increase in the degree of coupling between PNA and RSNA, indicating that the DMH-evoked increase in RSNA is not a consequence of increased central respiratory drive. arterial pressure; renal sympathetic nerve activity; heart rate; psychological stress
doi:10.1152/ajpregu.00503.2007 pmid:17715179 fatcat:74aymgrgpjdrvewizcaegx7rj4