Many of the current treatments have only a partial or temporary effects on some of the symptoms.

Tropisetron is an antagonist at the 5HT3 receptor that was developed as a treatment for emesis. In animal models, tropisetron, but not ondansetron, was shown to antagonize spatial navigation impairment in a complex spatial memory task (Pharm. Biochem. Behavior.

56 : 571,1997). The authors suggested, "the possible existence of other 5-HT3 receptor subtypes might help to explain the different behavioral effects of ondansetron, tropisetron and itasetron. "Recently, it has been reported that fibromyalgia patients treated with tropisetron showed a statistically significant reduction in their symptoms (Scand. J. Rheumatol. Suppl.

113: 46-55,2000). The positive effects of this drug in fibromyalgia patients were attributed to tropisetron's binding to the 5HT3 receptor.

Description of the invention We have now discovered that tropisetron acts as a potent partial agonist of the a7 nicotinic acetylcholine receptor. This discovery links the symptoms of FMS to activity of a7 receptors rather than those of 5HT3 receptors.

The a7 nicotinic acetylcholine receptors are abundant in cholinergic brain areas important to cognition and memory. This receptor has also been associated with the modulation of neurotransmission and the modulation of long-term potentiation (LTP). This receptor may also function as a filter to gate external sensory inputs, thus making it an attractive target for treatment of cognitive deficits such as those observed in FMS patients.

Many of the symptoms such as pain, memory loss, compromised attention, and irritable bladder exhibited by patients with FMS can be linked to activation or desensitization of the a7 receptor. We believe the etiology of FMS is linked to the a7 receptor and that patients with FMS would respond to treatment with a7 agonists, such as the compounds disclosed herein.

A variety of a7 agonists are known that are useful in all aspects of the present invention.

Accordingly, the present invention relates to the use of agonists of a7 nicotinic acetylcholine receptors to treat FMS. Therefore, in one aspect the present invention is directed to the treatment of FMS with a7 agonists. In a second aspect the invention is directed to the use of an a7 agonist to treat the symptoms of FMS. In another aspect the invention is directed to pharmaceutical compositions containing a7 agonists useful for the treatment or amelioration of FMS.

The invention relates to the use of an a7 agonist for the treatment or prophylaxis of fibromyalgia syndrome and fibromyalgia-related symptoms. The invention can be put into practice by clinical trials in which the alleviation of the symptoms in patients with FMS is measured in drug-treated and placebo controls.

In one aspect of the invention, the a7 agonist is a compound that has a Ki value of less than 1000 nM in the 1251_a-Bungarotoxin binding to rat hippocampal membrane assay.

In another aspect of the invention, the a7 agonist is a compound that has an ECso value of less than 30 uM in the functional rat oocyte assay.

In another aspect of the invention, the a7 agonist is a compound that has a K ; value of less than 1000 nM in the l25I-a-Bungarotoxin binding to rat hippocampal membrane assay and an ECso value in the functional rat oocyte assay of less than 30 uM.

Another aspect of the invention relates to a method for the manufacture of a medicament for the treatment or prophylaxis of fibromyalgia syndrome and fibromyalgia- related symptoms comprising an a7 agonist, wherein the a7 agonist is defined as described by any of the above embodiments.

We have discovered that the 5HT3 receptor antagonist tropisetron is a potent and selective partial agonist at the a7 receptor. In contrast, the structurally similar 5HT3 antagonist, ondansetron, was shown to lack activity at the a7 receptor.

Therefore, the memory effects of tropisetron are likely to arise from its action at the a7 receptor. Accordingly, we believe that the positive therapeutic activity of tropisetron in FMS patients is due to the action of this drug at the a7 receptor and not due to actions at the 5HT3 receptor as previously reported.

Brief description of the drawings: Fig. 1 shows the currents elicited in frog oocytes expressing mouse nAChR a7-receptors by acetylcholine or tropisetron.

Detailed Description of the Invention : In a first embodiment of the invention a suitable a7 agonist is spiro [1- azabicyclo [2.2. 2] octane-3,5'-oxazolidine-2'-one (Compound 1, Table 1). This compound is a selective a7 agonist with a wide safety margin. This compound is disclosed in U. S. Patent 5,902, 814 the disclosure of which is incorporated herein in its entirety by reference. This compound is active in animal models of memory and cognition.

In a second aspect of the invention a suitable a7 agonist is a compound as disclosed in PCT publication WO 01/60821 the disclosure of which is incorporated herein in its entirety by reference, having the structure : wherein: A is selected from D is oxygen or sulfur ; E is a single bond, oxygen, sulfur, or NR'° ; R is hydrogen or methyl; Arl is a 5-or 6-membered aromatic or heteroaromatic ring containing 0,1, 2 or 3 nitrogen, oxygen or sulfur atoms, wherein there is no more than 1 oxygen or sulfur atom; Ar2 is a 5-or 6-membered aromatic or heteroaromatic ring containing 0,1, 2 or 3 nitrogen, oxygen or sulfur atoms, wherein there is no more than 2 oxygen or sulfur atom; or an 8-, 9-or 10-membered fused aromatic or heteroaromatic ring system containing 0, 1, 2 or 3 nitrogen, oxygen or sulfur atoms, wherein there is no more than 2 oxygen or sulfur atoms; wherein if Ar2 is unsubstituted phenyl, then Arl is not pyrazolyl;

wherein the aromatic rings Arl and Ar2 are substituted with 0, 1, 2 or 3 substituents selected from halogen, C1-4alkyl, C2-4alkenyl, C2-4alkynyl, CN, N02, NR1R2, CH2NR1R2, OR3, CH20R3, COzR4 and CF3 ; but if Arl is phenyl and Ar2 is quinolynyl, then Ar2 is substituted with 0,1, 2 or 3 substituents selected from C1-4alkyl, C2-4alkenyl, C2-4alkynyl, CN, NOs, NR'R, CH2NR' OR3, CH20R3 and Co2R4 ; R', R2, and R3 are independently C1-4alkyl, aryl, heteroaryl, C (O) R5, C (O) NHR6, C (O) R7, SO2R8 ; or Rl and R2 may together be (CH2) jG (CH2) k where G is oxygen, sulfur, NR9, or a single bond; j is 2, 3 or 4 ; k is 0, 1 or 2 ; R4, R5, R6, R7, R8, R9, and Rl° are independently Cl 4alkyl, aryl, or heteroaryl; or an enantiomer thereof and pharmaceutically acceptable salts thereof; with the provisos that: (1) if D represents oxygen, E represents a single bond, and A represents: and either Arl or Ar2 represents a pyrazole ring, then all optional substituents on the pyrazole ring shall be hydrogen; and (2) if Arl represents a pyridine ring, Ar2 represents an aryl ring, and A represents: then all optional substituents on the pyridine ring shall be hydrogen.

Particular compounds that are embodiments of this aspect of the inventions are compounds below: N-(1-azabicyclo [2.2. 2] oct-3-yl) (3-phenylbenzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (2-thienyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3-thienyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (4-phenylthiophene-2-carboxamide), compound 3, Table 1; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5-phenylthiophene-3-carboxamide);

N-(1-azabicyclo [2.2. 2] oct-3-yl) (5-phenylthiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5-phenylfuran-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-pyridyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-pyridyl) furan-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-furyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-furyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-thienyl) furan-2-carboxamide); N (l-azabicyclo [2.2. 2] oct-3-yl) (5- (3-thienyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-fluorophenyl) furan-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3-pyridyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3-methoxyphenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (2-methoxyphenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3- (N-acetylamino) phenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3-fluorophenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3-methylphenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (3, 5-dichlorophenyl) benzamide); N (l-azabicyclo [2.2. 2] oct-3-yl) (3- (2-naphthyl) benzamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (3- (4-fluorophenyl) benzamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-benzo [b] furanyl) furan-2-carboxamide); N- (l-azabicyclo [2.2. 2] oct-3-yl) (5- (4-pyridyl) furan-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-methoxyphenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-methoxyphenyl) furan-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (4-fluorophenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-naphthyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-methylphenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (4-pyridyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-pyridyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (2-pyridyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (4- (2-pyridyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (4- (4-pyridyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (4- (3-pyridyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3- (N-acetylamino) phenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-nitrophenyl) furan-2-carboxamide);

N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-trifluororiiethylphenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-chlorophenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5-(3-(N-acetylamino) phenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-fluorophenyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-methoxyphenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-ethoxyphenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3, 5-dimethylisoxazol-4-yl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3, 5-dimethylisoxazol-4-yl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-aminophenyl) thiophene-2-carboxamide); N- (l-azabicyclo [2.2. 2] oct-3-yl) (5- (3-pyridyl) thiophene-3-carboxamide); N (l-azabicyclo [2.2. 2] oct-3-yl) (5- (4-chlorophenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-pyridyl) thiazole-3-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yi) (5- (4-pyridyl) thiazole-3-carboxamide) ; N (l-azabicyclo [2.2. 2] oct-3-yl) (5-(3-(N, N-dimethylamino) phenyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (8-quinolinyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2. 2.2] oct-3-yl) (5- (3-cyanophenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3- (N-methylamino) phenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-hydroxyphenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-pyridylamino) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-chlorophenyl) thiophene-2-carboxamide) ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) (5- (3- (4-morpholinyl) phenyl) thiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3- (aminomethyl) phenyl) thiophene-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5-phenoxythiophene-2-carboxamide) ; N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-aminophenyl) furan-2-carboxamide) N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3- (N, N-dimethylamino) phenyl) furan-2-carboxamide); N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3-formylphenyl) thiophene-2-carboxamide), or N-(1-azabicyclo [2.2. 2] oct-3-yl) (5- (3- (hydroxymethyl) phenyl) thiophene-2-carboxamide) or an enantiomer thereof, or a pharmaceutically-acceptable salt thereof.

In a third aspect of the invention a suitable a7 agonist is a compound as disclosed in PCT publication WO 01/29034 the disclosure of which is incorporated herein by reference in its entirety, having the structure:

wherein: A represents a moiety selected from: R represents hydrogen or methyl; R1 and R2 are independently hydrogen, or C1-C4 alkyl ; R3 and R4 are independently hydrogen, C 1-C4 alkyl or SAr, provided that at least one of R3 and R4 is SAr ; Ar represents a 5-or 6-membered aromatic or heteroaromatic ring containing zero to three nitrogen atoms, zero or one oxygen atom, and zero or one sulfur atom or an 8-, 9-or 10- membered fused aromatic or heteroaromatic ring system containing zero to four nitrogen atoms, zero to one oxygen atom, and zero to one sulfur atom which may optionally be substituted with one or more substituents selected from: hydrogen, halogen, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, aryl, heteroaryl, -CO2R5, -CN, -NO2, -NR6R7, -CF3, - OR' ; R5, R6, R7, and R8 are. independently hydrogen, Cl-C4 alkyl, aryl, heteroaryl, -C (O) R9,-C (O) NHRl°,-C (O) Rll,-SO2Rl2 ; or, R6 and R7 may together be (CH2) jQ (CH2) k where Q is O, S, NR or, a bond ; j is 2 to 7; k is 0 to 2 ; R9, R10, R", R12, and R13, are independently C1-C4 alkyl, aryl, or heteroaryl; or an enantiomer thereof, and the pharmaceutically acceptable salts thereof.

Particular compounds that are embodiments of this aspect of the inventions are: N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (phenylthio) propenamide] hydrochloride; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (4-methylphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (4-methylphenylthio) propenamide];

N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (3-methylphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (3-methylphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-methylphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-methylphenylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (4-methoxyphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (4-methoxyphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (3-methoxyphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (3-methoxyphenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-methoxyphenylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-methoxyphenylthio) propenamide]; -N- (l-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3-(2-pyridylthio) propenamide] ;- N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-pyridylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (4-pyridylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (4-pyridylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-pyrimidinylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3-(2-pyrimidinylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-methyl-3-furanylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-methyl-3-furanylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-imidazolylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (phenylthio)-3- (methyl) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-benzothiazolylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-benzothiazolylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (l-methyl-2-imidazolylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (l-methyl-2-imidazolylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (5-methyl-1, 3,4-thiadiazol-2-ylthio) propenamide]; N-(1-aza-bicyclo [2. 2. 2] oct-3-yl) [E-3- (5-methyl-1, 3,4-thiadiazol-2-ylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3-(4-chlorophenylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-thiazolylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-thienylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-thienylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-benzoxazolylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-benzoxazolylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (4-trifluoromethyl-2-pyrimidinylthio) propenamide];

N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (4-fluorophenylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (4-fluorophenylthio) propenamide] ; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (2-thiazolo [4,5-b] pyridylthio) propenamide] ; (R)-N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (2-thiazolo [4,5-b] pyridylthio) propenamide]; N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [Z-3- (3-fluorophenylthio) propenamide], or N-(1-aza-bicyclo [2.2. 2] oct-3-yl) [E-3- (3-fluorophenylthio) propenamide] ; or an enantiomer thereof, or a pharmaceutically-acceptable salt thereof In a fourth aspect of the invention a suitable a7 agonist is a compound as disclosed in U. S. Patent 6,110, 914 the disclosure of which is incorporated herein by reference in its entirety, having the structure: wherein n is 0 or 1 ; m is 0 or 1; p is 0 or 1 ; X is oxygen or sulfur; Y is CH, N or NO ; W is oxygen, H2 or F2 ; A is N or C (R2) ; G is N or C (R3) ; D is N or C (R4) ; with the proviso that no more than one of A, G, and D is nitrogen but at least one of Y, A, G, and D is nitrogen or NO; Rl is hydrogen or Cl 4alkyl ; R2, R3, and R4 are independently hydrogen, halogen, C1-4alkyl, C2-4alkenyl, C2-4alkynyl, aryl, heteroaryl, OH, OC1-4alkyl, CO2R1, -CN, -NO2, -NR5R6, -CF3, -OSO2CF3, or R2 and R3, or R3 and R4, respectively, may together form another six membered aromatic or heteroaromatic ring sharing A and G, or G and D, respectively, containing 0,1 or 2 nitrogen atoms, and substituted with one to two substituents independently selected from hydrogen, halogen, Cl 4alkyl, C2 4alkenyl, C2 4alkynyl, aryl, heteroaryl, OH, OCI-4alkyl, C02R',-CN,-N02,-NRSR6,-CF3,-OS02CF3 ;

Rs and R6 are independently hydrogen, C1-4alkyl, C (O) R7, C (O) NOR', C (O) OR9, SO2RI° or may together be (CH2) jQ (CH2) k where Q is 0, S, Null, or a bond; j is 2 to 7 ; kisOto2 ; R7, R8, R9, Rl°, and R11 are independently C 1-4alkyl, aryl, or heteroaryl, or an enantiomer thereof, and the pharmaceutically acceptable salts thereof.

Particular compounds that are embodiments of this aspect of the inventions are: spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine], Compound 2, Table 1; 5'-bromospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-phenylspiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 5'-nitrospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)- furo [2,3-b] pyridine] ; 1'-chlorospiro [1-azabicyclo [2.2. 2] octane-3, 2'-(3'H)-furo [2, 3-b] isoquinoline] ; 5'-(phenylcarboxamido) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- (phenylaminocarbonylamino) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3- b] pyridine]; 5'-(phenylsulfonylamido) spiro [1-azabicyclo [2.2. 2]octane-3,2'-(3'H)-furo [2,3-b] pyridine]; 5'-aminospiro [1-azabicyclo [2.2. 2] octane-3, 2'-(3'H)-furo [2,3-b] pyridine] ; 5'-N-methylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-N, N-dimethylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- N, N-diethylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-N-ethylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 5'-N-benzylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 5'-N-formamidospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-N-acetamidospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; spiro [1-azabicyclo [2.2. 2] octane-3, 2'-(3'H)-furo [2,3-b] isoquinoline]; spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] quinoline] ; 5'-ethenylspiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- (E)- (phenylethenyl) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2, 3-b]pyridine]; 5'- (4-morpholino) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-(1-azetidinyl) spiro [1-azabicyclo [2. 2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- (E)- (2- (4-pyridyl) ethenyl) spiro[1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-(E)-(2-(2-pyridyl)ethenyl) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- (2-trimethylsilylethynyl) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine];

5'-ethynylspiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 5'- (2-furyl) spiro [ 1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'- (3-pyridyl) spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; 5'-methylspiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine]; spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine-5'carbonitrile] ; spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine-5'carboxamide]; 5'-N'-(3-chlorphenyl)aminocarbonylminospiro[1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)- furo [2,3-b] pyridine]; 5'-N'- (2-nitrophenyl) aminocarbonylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)- . furo [2,3-b] pyridine]; 4'-chlorospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 4'-methoxyspiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2, 3-b] pyridine] ; 4'-phenylthiospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 4'-(N-2-aminoethyl) aminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 4'-phenylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 4'-methylaminospiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2,3-b] pyridine] ; 4'-(4-N-methylpiperazin-1-yl) spiro [ 1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [2, 3- b] pyridine] ; 4'-chloro-spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [3,2-c] pyridine] ; spiro [1-azabicyclo [2.2. 2] octane-3, 2'- (3'H)-furo [3,2-c] pyridine] ; spiro [1-azabicyclo [2.2. 2] octane-3, 2' (3'H)-furo [2,3-b] pyridine-7'-oxide] ; spiro [1-azabicyclo [2.2. 2] octane-3, 2' (3'H)-furo [2,3-b] pyridine-6'-carbonitrile] ; 6'-chlorospiro [1-azabicyclo [2.2. 2] octane-3, 2' (3'H)-furo [2,3-b] pyridine], or 6'-fluorospiro [1-azabicyclo [2.2. 2] octane-3, 2'(3'H)-furo [2,3-b] pyridines ; or an enantiomer, or a pharmaceutically-acceptable salt thereof.

Experimental: We discovered that the 5HT3 receptor antagonist tropisetron is a potent and selective partial agonist at the a7 receptor (Figure 1). In contrast, the structurally similar 5HT3 antagonist, ondansetron, lacked activity at the a7 receptor (Table 1).

In earlier work (Pharm. Biochem. Behavior. 56 : 571,1997) tropisetron, but not ondansetron, antagonized spatial navigation impairment in a complex spatial memory task in animal models suggesting that behavioral differences were not due to actions at he 5HT3 receptor.

Test A-Assay for affinity at a7 nAChR subtype 125I-a-Bungarotoxin (BTS) binding to rat hippocampal membranes.

Rat hippocampi were homogenized in 20 volumes of cold homogenisation buffer (HB): (in mM): tris (hydroxymethyl) aminomethane 50; MgCl2 1; NaCl 120; KCI 5: pH 7.4).

The homogenate was centrifuged for 5 min at 1000 g, the supernatant was saved and the pellet re-extracted. The pooled supernatants were centrifuged for 20 min at 12000 g, washed, and re-suspended in HB. Membranes (30-80 u. g) were incubated with 5 nM [125I] a-BTX, 1 mg/mL BSA (bovine serum albumin), test drug, and either 2 mM CaC12 or 0.5 mM EGTA [ethylene glycol-bis (p-aminoethylether)] for 2 h at 21 °C, and then filtered and washed four times over Whatman glass fiber filters (thickness C) using a Brandel cell harvester. Pre- treating the filters for 3 h with 1% (BSA/0. 01% PEI (polyethyleneimine) in water was critical for low filter blanks (0.07% of total counts per minute). Non-specific binding was described by 100 uM (-) -nicotine, and specific binding was typically 75%.

Test B-Assay for affinity to the 5-HT nAChR subtype [3H zacopride binding. Binding of 0. 5 nM [3H] zacopride was assessed essentially as described in Test A using rat small-bowel muscularis membranes suspended in 50 mM Tris ; 150 mM NaCl at pH 7.4. Incubation was continued for one hour.

Binding data analysis for Tests A and B ICso values and pseudo Hill coefficients (nH) were calculated using the non-linear curve fitting program ALLFIT (DeLean A, Munson P J and Rodbard D (1977) Am. J.

Physiol. , 235: E97-E102). Saturation curves were fitted to a one site model, using the non- linear regression program ENZFITTER (Leatherbarrow, R. J. (1987) ), yielding KD values of 1.67 and 0.7 nM for the [t25I]-a-BTX and JH] zacopride ligands respectively. Ki values were estimated using the general Cheng-Prusoff equation (A): Ki= [IC50]/((2+([ligand]/KD)n)1/n-1) (A) where a value of n=l was used whenever nH<1. 5 and a value of n=2 was used when UH>1. 5.

Samples were assayed in triplicate and were typically 5%. Ki values were determined using six or more drug concentrations. The compounds of the invention are compounds with binding affinities (K ;) of less than 1 uM in Test A, indicating that they are expected to have useful therapeutic activity by interacting at the a7 receptor (Table 1).

Table 1. Binding Affinities Compound Stereo-Binding Affinity chemistry (Ki/nM) a7 5HT3 1 (R) 91 24000 2 (R) 14 NA 3 (R) 1. 6 20000

Test C-Rat Oocyte Functional Assay Xenopus oocytes Xenopus laevis frogs (Xenopus I, Kalamazoo, MI) were anesthetized using 0.15% tricaine. Oocytes were removed to OR2 solution: (in mM) 82 NaCl, 2.5 KCI, 5 HEPES, 1.5 NaH2P04, 1 MgC12, 0.1 EDTA, pH 7.4. The oocytes were defolliculated by incubation in 25 mL OR2 containing 0.2% collagenase 1A (SIGMA) two times for 60 min on a platform vibrating at 1 Hz and stored in Leibovitz's L-15 medium. Oocytes were injected the following day. Leibovitz's L-15 medium contained 50 llg/mL gentomycin, 10 units/mL penicillin, and 10 llg/mL streptomycin.

Preparation and injection of cRNA Rat nAChR a7 was cloned in-house (Luhowskyj).

Non-polyadenylated cRNA was prepared from cDNA using message machine SP6 (Ambion) according to the manufacturer's instructions.

Recording The external recording solution consisted of (in mM) 90 NaCl, 1 KCI, 1 MgClz, 1 BaCl2, 5 HEPES, pH 7.4. Two-electrode voltage-clamp recording was carried out using an Oocyte Clamp amplifier (model OC 725C, Warner Inst. , Hamden, CT). Oocytes were impaled with two electrodes of 1-2 MQ tip resistance when filled with 3M KCl.

Recordings were begun when membrane potential became stable at potentials negative to- 20 mV. Membrane potential was clamped at-80 mV unless otherwise noted. ACh, (-) was purchased from SIGMA.

Calculation of current amplitude and curve fitting Current amplitude was measured from baseline to peak. ECso's, maximal effect, and Hill slopes were estimated by fitting the data to the logistic equation using GraphPad Prism (GraphPad Software, Inc. San Diego, CA) Figure 1 shows the effect of acetylcholine and tropisetron on oocytes expressing mouse nAChR a7. In the upper panel, representative traces of current elicited in oocytes expressing mouse nAChR a7 are illustrated. Traces shown are from the same oocyte; superfusion of acetylcholine and tropisetron begins at arrow (5 min between agonist applications). In the lower panel, concentration-response curve to acetylcholine and tropisetron are shown. Data are fit by the logistic equation.