Effects of RVLM Stimulation on Blood Pressure and Vasopressin-Like Levels in Brain Sites and Plasma are an Anesthetic Dependent. Rashid IH

Abstract

The study is sought to determine specific alteration in AVP-LI level of plasma and sites of the hypothalamic-neurohypophysial-system; supraoptic nucleus (SON), paraventricular nucleus (PVN), neurointermediate lobe (NIL), and median eminence (ME), related to effects of stress of different anesthetics and electrical stimulation of RVLM/C1area. Urethane or halothane anesthetized Wistar rats were subjected to intra-RVLM electrical stimulation of 10 sec train, 1msec pulse duration at 40 Hz, and 2V every 30s.  After 30min stimulation, AVP-LI extracted from plasma, NIL, ME, SON, and PVN and measured by RIA, were compared with that of sham-stimulated urethane- or halothane-anesthetized rats and unstimulated unanesthetized control rats. Data were expressed as mean ± S.E.M. and analyzed using as appropriate Student's paired or unpaired t-test, and one way ANOVA. The results demonstrates presence of differential effects of the used anesthetics on resting BP, and increased BP to RVLM-stimulation, as well as a differential reduction in AVP-LI level which is significant (p<0.05) with urethane in SON NIL, ME, and blood plasma, but not in PVN, which is in contrast to urethane was significant with halothane, suggest a central role for halothane on release of PVN-AVP vs. role for urethane on the release of AVP at the level of hypothalamic-neurohypophysial-system. However, stimulation of RVLM abolished the regional specificity of  anesthetics on SON vs PVN-AVP levels, indicated neither anesthetic prevented the central mechanisms involved in the response of AVP neurons to RVLM stimulation. In conclusion, halothane is preferred for examining the effects of RVLM-stimulation on AVP changes, whereas in term of their effects on the pressor response to stimulation of the RVLM area, urethane appears preferable.