Effects of calcium-activated potassium channel modulators on afterhyperpolarizing potentials in identified motor and mechanosensory neurons of the medicinal leech.

Calcium-activated potassium (KCa) channels contribute to multiple neuronal properties including spike frequency and afterhyperpolarizing potentials (AHPs). KCa channels are classified as KCa1.1, KCa2, or KCa3.1 based on single-channel conductance and pharmacology. Ca2+-dependent AHPs in vertebrates are categorized as fast, medium, or slow. Fast and medium AHPs are generated by KCa1.1 and KCa2 channels, respectively. The KCa subtype responsible for slow AHPs is unclear. Prolonged, Ca2+-dependent AHPs have been described in several leech neurons. Unfortunately, apamin and other KCa blockers often prove ineffective in the leech. An alternative approach is to utilize KCa modulators, which alter channel sensitivity to Ca2+. Vertebrate KCa2 channels are targeted selectively by the positive modulator CyPPA and the negative modulator NS8593. Here we show that AHPs in identified motor and mechanosensory leech neurons are enhanced by CyPPA and suppressed by NS8593. Our results indicate that KCa2 channels underlie prolonged AHPs in these neurons and suggest that KCa2 modulators may serve as effective tools to explore the role of KCa channels in leech physiology.

Live, attenuated varicella zoster vaccination of an immunocompromised patient.

A vaccine for the prevention of herpes zoster outbreaks in adults over the age of 60 years has recently been approved. A 76-year-old white female with a history of recurrent left axillary breast cancer undergoing chemotherapy was given a Zostavax injection by her primary care physician. Eight days later, the patient developed a rash. Given the recent administration of live, attenuated varicella zoster virus (VZV), a diagnosis of disseminated cutaneous herpes zoster was made. The patient was treated successfully with a course of famciclovir for 10 days and cephalexin for 7 days for a secondary bacterial infection. A review of the medical literature disclosed no reports of Zostavax given to adult cancer patients immunocompromised by systemic chemotherapy. Therefore, we believe this report is the first to describe the consequences of Zostavax administration to such a host. Clinicians should take care to review contraindications and precautions prior to administering the Zostavax vaccine.