TRANSGENIC MICE OVER-EXPRESSING HUMAN -AMYLOID HAVE FUNCTIONAL NICOTINIC ALPHA 7 RECEPTORS J. P. SPENCER, a * A. WEIL, a K. HILL, a I. HUSSAIN, a J. C. RICHARDSON, a F. S. CUSDIN, b Y. H. CHEN c AND A. D. RANDALL a a Neurology and GI CEDD, GlaxoSmithKline, Harlow, Essex CM19 5AW, UK b Genetics Research, GlaxoSmithKline, Harlow, Essex CM19 5AW, UK c Discovery Research, GlaxoSmithKline, Stevenage, Hertfordshire SG1 2NY, UK Abstract—A potentially major factor in the development of Alzheimer’s disease is the enhanced production of soluble -amyloid peptide fragments amyloid  peptide 1– 40 and amy- loid  peptide 1– 42 . These amyloid peptides are generated by cleavage of the amyloid-precursor protein and aggregate spontaneously to form amyloid plaques, which are a classical pathological hallmark in Alzheimer’s disease. Although the precise mechanisms are unknown, it is widely believed that amyloid peptides initiate the degenerative process, resulting in subsequent cognitive decline. One interaction of amyloid  peptide that may contribute to an impairment of cognition is its high affinity binding to the alpha 7 nicotinic receptor; a receptor shown to be important for cognition in a number of studies. There is some controversy, however, whether amy- loid  peptide inhibits or activates this receptor. We have cloned and stably expressed the human alpha 7 receptor and investigated its interaction with amyloid  peptide using patch clamp electrophysiology. Human alpha 7 was activated in a concentration-dependent fashion by nicotine, acetylcho- line and choline and potently inhibited by methyllycaconitine citrate. The responses were inwardly rectifying and exhibited rapid activation, desensitization and deactivation. Amyloid  peptide 1– 42 antagonized human 7 responses in a partially re- versible fashion; no agonist effects of amyloid  peptide 1– 42 were detected. A similar inhibition of mouse alpha 7 was also observed. In addition, we have assessed the function of na- tive alpha 7 receptors in hippocampal slices prepared from transgenic mice that over-express human amyloid. Despite this clear inhibition of recombinant receptors, hippocampal GABAergic interneurones in slices from -amyloid over-ex- pressing mice still possess alpha 7 receptor-mediated currents. © 2005 Published by Elsevier Ltd on behalf of IBRO. Key words: Alzheimer’s disease, transgenic, hippocampus, memory, ion channel, electrophysiology. Alzheimer’s disease (AD) is the most common form of dementia in the elderly. Clinically the disease is character- ized by a progressive impairment in cognitive function along with numerous other symptoms. The major patho- logical hallmark in AD is the appearance of extracellular neuritic plaques primarily composed of aggregated forms of the amyloid  (A) peptide. Although the etiology of AD is unknown, it is generally believed that the generation of A via the proteolytic cleavage of the membrane bound amyloid precursor protein (APP) is one of the main initiat- ing factors of the disease (Atwood et al., 2003). Indeed, A is widely considered to be responsible for the early loss of cholinergic cells and the subsequent degeneration of cho- linergic projections to the forebrain; the loss of which is hypothesized to play a major role in AD-related cognitive decline (Bartus et al., 1982). In addition to the loss of cholinergic projections, there is some evidence suggesting that cholinergic receptor sys- tems are also altered in AD (Flynn et al., 1995; Nordberg, 2001). Both muscarinic and nicotinic receptors are thought to play a role in cognition, disruption of which may contrib- ute to the decline in memory observed in AD. For example, nicotine has been shown to have pro-cognitive functions since it can improve memory and attention both in humans and experimental animals (Levin and Simon, 1998; Rusted et al., 2000). One nicotinic receptor subtype which is believed to mediate the pro-cognitive effects of nicotine is the alpha 7 (7) receptor (Levin, 2002). The 7 receptor is homo- pentameric (Couturier et al., 1990), with a calcium perme- ability roughly equal in magnitude to that of the NMDA receptor (Seguela et al., 1993; Fucile et al., 2003). 7 Is highly expressed in the hippocampus and cortex (Dominguez et al., 1994; Bina et al., 1995; Fabian-Fine et al., 2001); regions of the brain intimately associated with learning and memory function. 7 Receptors have been shown to be located both presynaptically, where they modulate neurotransmitter release (McGehee et al., 1995; Gray et al., 1996), and, perhaps more controversially, postsynaptically, where they have been reported to medi- ate fast synaptic transmission (Gray et al., 1996; Zhang et al., 1996; Frazier et al., 1998; Bradaia and Trouslard, 2002; Hatton and Yang, 2002; Matsubayashi et al., 2004). The 7 receptor has received considerable attention with regard to cognitive enhancement and AD, since specific 7 agonists improve learning and memory in a variety of animal models (Levin et al., 1999; Kem, 2000; Hatton and Yang, 2002; Van Kampen et al., 2004). Interestingly A peptides have been shown to exhibit picomolar affinity for 7 receptors (Wang et al., 2000b), and to co-localize with 7 receptors in samples of post- mortem AD tissue (Wang et al., 2000a). This indicated that A-mediated disruption of normal 7 receptor function could contribute to the impaired cognition observed in AD. *Corresponding author. Tel: +44-01279-622423; fax: +44-01279-622555. E-mail address: jon_p_spencer@gsk.com (J. P. Spencer). Abbreviations: ACh, acetylcholine; aCSF, artificial cerebrospinal fluid; AD, Alzheimer’s disease; APP, amyloid precursor protein; A, amyloid  peptide; MLA, methyllycaconitine citrate; PS-1, presenilin-1; V–I, voltage– current; 7, alpha 7 nicotinic receptor. Neuroscience 137 (2006) 795– 805 0306-4522/06$30.00+0.00 © 2005 Published by Elsevier Ltd on behalf of IBRO. doi:10.1016/j.neuroscience.2005.10.007 795