Tamapin, a venom peptide from the Indian red scorpion (Mesobuthus tamulus) that targets small conductance Ca2+-activated K+ channels and afterhyperpolarization currents in central neurons.

The biophysical properties of small conductance Ca(2+)-activated K(+) (SK) channels are well suited to underlie afterhyperpolarizations (AHPs) shaping the firing patterns of a conspicuous number of central and peripheral neurons. We have identified a new scorpion toxin (tamapin) that binds to SK channels with high affinity and inhibits SK channel-mediated currents in pyramidal neurons of the hippocampus as well as in cell lines expressing distinct SK channel subunits. This toxin distinguished between the SK channels underlying the apamin-sensitive I(AHP) and the Ca(2+)-activated K(+) channels mediating the slow I(AHP) (sI(AHP)) in hippocampal neurons. Compared with related scorpion toxins, tamapin displayed a unique, remarkable selectivity for SK2 versus SK1 ( approximately 1750-fold) and SK3 ( approximately 70-fold) channels and is the most potent SK2 channel blocker characterized so far (IC(50) for SK2 channels = 24 pm). Tamapin will facilitate the characterization of the subunit composition of native SK channels and help determine their involvement in electrical and biochemical signaling.

Fibrinolytic phenomenon in leprosy.

Fibrinolytic activity in eighty-one patients with different types of leprosy and thirty-two normal healthy controls was studied by Euglobulin Lysis Time Method, Fibrinolytic activity was markedly decreased in patients with lepromatous leprosy and those with ENL reaction. Decline in fibrinolytic activity during ENL was independent of frequency of attacks. Fibrinolytic activity was partly restored after subsidence of ENL reaction, though it failed to attain normal levels. Cutaneous vasculitis seems to be most probable cause of fall in fibrinolytic activity in lepromatous leprosy and ENL reaction.