Key result
Injection of lidocaine in the ventromedial periaqueductal gray significantly attenuated the pressor response produced by intracerebroventricular administration of angiotensin II in conscious rats.
Why the study?
Does lidocaine injection in specific periaqueductal gray sites attenuate the pressor response to central angiotensin II in rats?
Does lidocaine injection in specific periaqueductal gray sites attenuate the pressor response to central angiotensin II in rats?
The study identifies two functionally and anatomically distinct sites in the rostral periaqueductal gray that mediate different cardiovascular responses to electrical and chemical stimulation of the AV3V region.
Should not change clinical practice; hypothesis-generating for ventromedial periaqueductal gray mediation of central angiotensin II pressor responses.
The present studies were undertaken to determine the role of rostral periaqueductal gray (PAG) in mediating the pressor effect produced by intracerebroventricular (icv) injection of angiotensin II (ANG II, 200 ng). Two functionally and anatomically distinct sites were identified in rostral PAG: a dorsomedial site involved in the hemodynamic responses produced by electrical stimulation of the anteroventral third ventricle (AV3V) region and a ventromedial site required for the pressor response elicited by icv administration of ANG II. In Saffan-anesthetized rats, injection of lidocaine (LIDO, 4%) in dorsomedial PAG, but not in ventromedial PAG, significantly attenuated the decrease in hindquarter resistance (HQR) produced by electrical stimulation of the AV3V region, and the poststimulatory increase in mean arterial pressure (MAP) and HQR. The injection of LIDO in ventromedial PAG had no effect on the hemodynamic responses produced by electrical stimulation of the AV3V region in anesthetized rats but significantly attenuated the pressor response produced by icv administration of ANG II in conscious rats. The hypothesis that these two sites receive separate projections was addressed by microinjecting two retrogradely transported fluorescent dyes, Fluoro-Gold and Fast Blue. The anatomic findings suggest that separation of the pathways activated by electrical and chemical stimulation of the AV3V region occurs at the level of rostral PAG.
No takes yet. Share an insight, caveat, or question.
Portis et al. (1993) studied this question. Injection of lidocaine in ventromedial or dorsomedial PAG was evaluated on Hemodynamic responses and pressor response to icv ANG II. Injection of lidocaine in the ventromedial periaqueductal gray significantly attenuated the pressor response produced by intracerebroventricular administration of angiotensin II in conscious rats.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: