Impaired regulation function in cardiovascular neurons of nucleus tractus solitarii in streptozotocin-induced diabetic rats

This study characterizes neural firing activity of the nucleus tractus solitarii (NTS) and baroreflex sensitivity (BRS) in streptozotocin (STZ)-induced diabetic rats relative to control rats by implantation of multi-wire electrode into rat NTS for direct monitoring of barosensitive NTS neurons before and after baroreflex system challenge by phenylephrine (PE) injection. NTS firing data is correlated with arterial pressure for both control and diabetic rats. In control rats, NTS firing rate and systolic arterial pressure correlate significantly with both pre-PE (baseline) and post-PE (p < 0.01). In STZ-induced diabetic rats, positive correlation is observed only after PE injection (p < 0.05). Although NTS firing rate was not significantly different between control and diabetic rats (p = 0.085) in the baseline condition, it was significantly reduced in STZ-induced diabetic rats (p = 0.042) with adjustment for BRS. After PE injection, NTS firing rate is significantly lower in diabetic rats relative to control rats (p < 0.01). With adjustment for BRS, multivariate analysis shows that diabetes is independently associated with NTS firing rate after PE injection (p = 0.034). Prior physiological and immunofluorescent studies found differing NTS data for control and diabetic rat only after PE challenge, but our data show diabetes-induced barosensitive NTS impairment in the baseline condition for STZ-induced diabetic rats. This latter finding suggests greater sensitivity of multi-wire electrode study of NTS relative to earlier methods.