Israel Medical Association Journal

Reversible cerebral vasoconstriction syndrome (RCVS) comprises a group of conditions characterized by reversible vasoconstrictions of cerebral arteries. Clinical manifestations include sudden-onset severe headaches with or without additional neurologic signs and symptoms [1].

The incidence of RCVS is 2.7 cases per million adults. It predominantly affects women, and about 9% of all RCVS cases occur during the postpartum period [2,3]. Other possible precipitating factors, such as subarachnoid hemorrhage, ischemic stroke, intracranial hemorrhage, and exposure to vasoactive drugs, have also been reported in association with RCVS [2]. The exact pathophysiology of RCVS is not well understood, although hormonal influences have been suggested as possible contributing factors.

Alkalosis-induced cerebral vasoconstriction is described but not well understood. Hyperventilation is commonly used in neurologic patients to decrease intracranial pressure and cerebral blood flow. Hyperventilation causes cerebral vasoconstriction directly by hypocapnia and may indirectly affect through alkalosis.

We present a case of RCVS in a postpartum patient admitted to the intensive care unit (ICU) with severe metabolic alkalosis necessitating hemodialysis.

Background: Splanchnic nerve stimulation evokes adrenomedullary catecholamine secretion via acetylcholine release and occupation of nicotinic cholinergic receptors on chromaffin cells.

Objectives: To assess whether among cultured adrenomedullary cells there exists a population that tonically secretes acetylcholine. If so, then blockade of enzymatic breakdown of acetylcholine by addition of a cholinesterase inhibitor to the medium would increase occupation of nicotinic receptors by endogenous acetylcholine and thereby induce catecholamine release.

Methods: Primary cultures of bovine adrenomedullary cells in 24-well plates (1 million cells per well) were incubated after 48–72 hours with fresh incubation medium (control), medium with added secretagogues (nicotine, angiotensin II, or K+) or the acetylcholinesterase inhibitor, edrophonium (10-7 to 10-³ M), for 1–20 minutes. Fractional release rates of epinephrine, norepinephrine and dopamine were compared to a control. We also examined whether co-incubation with edrophonium enhanced the effects of the secretagogues. All experiments were performed in quadruplicate and repeated three times.

Results: Nicotine, angiotensin II, and K+ each elicited time-related release of epinephrine, norepinephrine and dopamine by up to fourfold compared to the control. At all tested concentrations, edrophonium had no such effect. Co-incubation with edrophonium also failed to augment the secretory responses to nicotine, angiotensin II, or K+.

Conclusion: Bovine adrenomedullary cells in primary culture do not include a population of tonically active cholinergic cells.