Calcium responses induced by Tat30-86 (500nM) in cerebral cortical neurons. A, Tat30-86 produced a fast and transitory increase in [Ca2+]i in this neuron; a similar response was produced in 43% of the cells tested. B, calcium oscillations produced by Tat30-86 in this neuron; this type of response was present in 21% of the cells tested. C, Tat30-86 produced a spike followed by a plateau in 9% of cells tested. D, Heat inactivated Tat30-86 (hi-Tat) did not increase [Ca2+]i in any of the 85 neurons tested. E, pretreatment with AP-5 (50 μM) and CNQX (10 μM) abolished the plateau, while preserving the fast, transient [Ca2+]i increase.