The slow afterhyperpolarization (sAHP) that follows an action potential in many central and peripheral neurons is due to the activation of voltage-independent, Ca2+-activated K+ channels. Hippocampal CA1 neurons have served as models for studying the sAHP and the underlying current, the IsAHP. The results of studies performed over the past two decades show that the sAHP has a profound influence on neuronal intrinsic excitability, being responsible for spike-frequency adaptation that regulates burst frequency. The sAHP is one of the principal targets for the ascending modulatory neurotransmitter systems that are involved in regulating the sleep-wake cycle, arousal, attention, and in modulating sensory processing, behaviors, emotions and memory consolidation. Importantly, the (I)sAHP decreases following learning, increasing intrinsic excitability. In addition, the (I)sAHP increases with age, reducing intrinsic excitability, and this age-related increase plays an integral role in the learning impairments that accompany normal aging. A similar increase in the (I)sAHP occurs in Alzheimer's disease models. The (I)sAHP channels are defined by: Ca2+-dependence, voltage-independence, K+-selectivity, and invariant slow activation kinetics. Indistinguishable (I)sAHPs have been recorded from hippocampal CA1and CA3, layers II-III of the cortex, (lateral) amygdala, and (midline) thalamus. SK channels and M-channels have been suggested to form the (I)sAHP channels, but there is abundant contradictory evidence. Therefore, despite decades of work, the molecular identity of the (I)sAHP channels remains to be determined. We have used bioinformatic genome analysis coupled with the functional characteristics of cloned channels, results from knockout mice, and detailed cell-type expression data for all K+ channel genes to identify 2 high priority candidates for the (I)sAHP channels. We propose to use a combination of molecular biological and electrophysiological techniques to test these candidates and identify clones encoding the pore-forming subunits of the (I)sAHP channels. Determining the identities of the (I)sAHP channels will provide a powerful target for therapeutic approaches to multiple central pathologies such as Alzheimer's disease, schizophrenia, epilepsy, attention deficit syndrome, and sleep disorders, as well as for cognitive impairment during normal aging.
The slow afterhyperpolization (AHP) channels regulate intrinsic excitability in many central neurons, and their activity is important for normal sleep-wake cycle, arousal, attention, and in modulating sensory processing, behaviors, emotions and memory consolidation. We will clone the slow AHP channels and define their requisite components. Determining the identities of the slow AHP channels will provide a powerful target for therapeutic approaches to multiple central pathologies such as Alzheimer's disease, schizophrenia, epilepsy, attention deficit syndrome, and sleep disorders, as well as for cognitive impairment during normal aging.
