Effect of acute adrenalectomy on sympathetic responses to peripheral lipopolysaccharide or central PGE(2)

The impact of plasma corticosterone levels on the sympathetic nervous syste m (SNS) response to intravenous lipopolysaccharide (LPS) or intracerebroven tricular injections of PG was studied in anesthetized (urethanchloralose) m ale Sprague-Dawley rats. For this, electrophysiological recordings of splen ic and renal nerves were completed in control or adrenalectomized (ADX) rat s. LPS (10 mu g iv) similarly increased splenic and renal nerve activity in control rats with a shorter onset latency for the splenic nerve. Acute ADX enhanced the response of both nerves to LPS (P < 0.005) and reduced the on set latency of the renal nerve (P < 0.05). PGE(2) (2 mu g icv) rapidly incr eased the activity of both nerves but preferentially (magnitude and onset l atency) stimulated the renal nerve (P < 0.05). The magnitude of the splenic nerve response to PGE(2) was unaffected hy ADX. Unexpectedly, PGE(2) was l ess effective at stimulating renal nerve activity in ADX animals relative t o intact controls (P < 0.05). Pretreatment of ADX rats with a CRF antagonis t {[D-Phe(12), Nle(21,38), C alpha-MeLeu(37)]CRF-(12-41)} reversed this eff ect such that the renal nerve responded to central PGE(2) to a greater exte nt than the splenic nerve (P < 0.05), as was the case in non-ADX rats. Thes e data indicate that enhanced sensitivity of central sympathetic pathways d oes not account for the enhanced SNS responses to LPS in ADX rats. Also, a CRF-related process appears to diminish renal sympathetic outflow in ADX ra ts.