Methamphetamine (Meth) is a potent and commonly abused psychostimulant. Meth alters neuron and astrocyte activity; yet the underlying mechanism(s) is not fully understood. Here we assessed the impact of acute Meth on human fetal astrocytes (HFAs) using whole-cell patch-clamping. We found that HFAs displayed a large voltage-gated K+ efflux (I-Kv) through K-v/K-v-like channels during membrane depolarization, and a smaller K+ influx (I-kir) via inward-rectifying K-ir/K-ir-like channels during membrane hyperpolarization. Meth at a recreational' (20M) or toxic/fatal (100M) concentration depolarized resting membrane potential (RMP) and suppressed IKv/Kv-like. These changes were associated with a decreased time constant (?), and mimicked by blocking the two-pore domain K+ (K-2P)/K-2P-like and K-v/K-v-like channels, respectively. Meth also diminished IKir/Kir-like, but only at toxic/fatal levels. Given that Meth is a potent agonist for the trace amine-associated receptor type-1 (TAAR1), and TAAR1-coupled cAMP/cAMP-activated protein kinase (PKA) cascade, we further evaluated whether the Meth impact on K+ efflux was mediated by this pathway. We found that antagonizing TAAR1 with N-(3-Ethoxyphenyl)-4-(1-pyrrolidinyl)-3-(trifluoromethyl)benzamide (EPPTB) reversed Meth-induced suppression of IKv/Kv-like; and inhibiting PKA activity by H89 abolished Meth effects on suppressing IKv/Kv-like. Antagonizing TAAR1 might also attenuate Meth-induced RMP depolarization. Voltage-gated Ca2+ currents were not detected in HFAs. These novel findings demonstrate that Meth suppresses IKv/Kv-like by facilitating the TAAR1/G(s)/cAMP/PKA cascade and altering the kinetics of K-v/K-v-like channel gating, but reduces K-2P/K-2P-like channel activity through other pathway(s), in HFAs. Given that Meth-induced decrease in astrocytic K+ efflux through K-2P/K-2P-like and K-v/K-v-like channels reduces extracellular K+ levels, such reduction could consequently contribute to a decreased excitability of surrounding neurons.

Human Immunodeficiency Virus type 1 (HIV-1) infection induces neurological and neuropsychological deficits, which are associated with dysregulation of the medial prefrontal cortex (mPFC) and other vulnerable brain regions. We evaluated the impact of HIV infection in the mPFC and the therapeutic potential of targeting over-active voltage-gated L-type Ca2 + channels (L-channel) and NMDA receptors (NMDAR), as modeled in HIV-1 transgenic (Tg) rats. Whole-cell patch-clamp recording was used to assess the membrane properties and voltage-sensitive Ca2 + potentials (Ca2 + influx) in mPFC pyramidal neurons. Neurons from HIV-1 Tg rats displayed reduced rheobase, spike amplitude and inwardly-rectifying K+ influx, increased numbers of action potentials, and a trend of aberrant firing compared to those from non-Tg control rats. Neuronal hyper-excitation was associated with abnormally-enhanced Ca2 + influx (independent of NMDAR), which was eliminated by acute L-channel blockade. Combined chronic blockade of over-active L-channels and NMDARs with open-channel blockers abolished HIV effects on spiking, aberrant firing and Ca2 + potential half-amplitude duration, though not the reduced inward rectification. In contrast, individual chronic blockade of over-active L-channels or NMDARs did not alleviate HIV-induced mPFC hyper-excitability. These studies demonstrate that HIV alters mPFC neuronal activity by dysregulating membrane excitability and Ca2 + influx through the L-channels. This renders these neurons more susceptible and vulnerable to excitatory stimuli, and could contribute to HIV-associated neuropathogenesis. Combined targeting of over-active L-channels/NMDARs alleviates HIV-induced dysfunction of mPFC pyramidal neurons, emphasizing a potential novel therapeutic strategy that may effectively decrease HIV-induced Ca2 + dysregulation in the mPFC.