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.
Effects of RVLM Stimulation on Blood Pressure and Vasopressin-Like Levels in Brain Sites and Plasma are an Anesthetic Dependent. Rashid IH
RVLM/C1
AVP
urethane
halothane
plasma
NIL
ME
SON
PVN