A NEUROPEPTIDE THAT DRAMATICALLY ENHANCES LEARNING AND MEMORY POTENTIAL FOR COGNITIVE DRUG DEVELOPMENT John M. Stewart Department of Biochemistry University of Colorado Medical School

Substance P (SP) is a neuropeptide. It is synthesized by neurons and used as a neurotransmitter, neuromodulator, and neurohormone. SP has the structure: Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-amide SP performs many functions in both the central and peripheral nervous systems (CNS and PNS). PNS Functions: Sensory neurotransmitter for pain and other signals Neurohormone for smooth muscle contraction in gut and vasculature CNS Functions: Regulation of learning and memory Regulation of behavior Central regulation of blood pressure Stimulation of amine neurotransmitter release (Dopamine)

SUBSTANCE P RECEPTORS All neurotransmitters act via membrane-imbedded protein receptors. SP receptors are coupled to GTP-binding proteins (G-proteins) for action. There are 2 receptors for SP in the CNS: NK-1 and SP-N receptors. NK-1 receptors bind SP(5-11) (SP-C) and shorter C-terminal fragments SP-N receptors bind SP(1-7) (SP-N) The SP active fragments are produced by specific enzymes that cleave SP. Neprilysin (NEP, ) yields SP(5-11) (SP-C). Prolyl endopeptidase yields SP-(1-7) (SP-N).

PROGRESS OF SP RECEPTOR RESEARCH NK-1 receptors are well known (cloned, sequenced, expressed in cells) SP-N receptors have not been characterized We are now actively working to clone, sequence and express SP-N receptors Expressed SP-N receptors are the required tool to find new drugs to enhance learning and memory (Cognitive Enhancement). SP-N produces no effects in the periphery.

SP HAS POWERFUL EFFECTS ON LEARNING AND MEMORY SP-C Destroys learning and memory SP-N Strongly enhances learning and memory These effects are mediated by the Nucleus Accumbens (these results are from experiments in rats and mice)

A PROGRAM OF RESEARCH ON SP-N 1. Clone, sequence and express SP-N receptors (work in progress) 2. Locate brain locations and circuitry of SP-N receptors 3. Synthesize SP-N agonists that will enter the brain (cross the BBB) 4. Develop new drugs for Cognitive Enhancement, Alzheimer’s and Parkinson’s

POTENTIAL FOR DRUG DEVELOPMENT SP-N Agonists for Cognitive Enhancement SP-N Agonists for Alzheimer’s and Parkinson’s SP-N Agonists for new analgesics SP-C Antagonists for schizophrenia

SUBSTANCE P REGULATES CNS DOPAMINE RELEASE SP-C stimulates dopamine release in the mesolimbic system This circuit is over-active in schizophrenia SP-N stimulates dopamine release in the nigro-striatal motor system This circuit is failing in Parkinson’s disease Drugs based on SP-C and SP-N offer promise of fully selective drugs for these diseases. Present drugs have bad cross-over side effects: L-DOPA for Parkinson’s causes Schizophrenia-like symptoms Neuroleptics for schizophrenia cause Parkinson-like symptoms (tardive dyskinesia)

ACTIONS OF SUBSTANCE P AND FRAGMENTS ON BEHAVIOR TESTINTACT SP SP-NSP-C Learning/Memory EnhancesEnhancesBlocks Normal MotorMixedIncreasesReduces Functions Stress-Motivated MixedReducesIncreases Behaviors AggressionInhibitsInhibitsIncreases Pain ResponsesInhibitsInhibitsIncreases

SUBSTANCE P AND ALZHEIMER’S DISEASE Toxic symptoms are caused by the amyloid A  peptide produced by abnormal processing of precursor protein (APP) SP is deficient in Alzheimer’s brains SP-N prevents toxic symptoms of A  peptide Drugs based on SP-N may help Alzheimer’s disease

SUBSTANCE P AND PAIN SENSATIONS SP is a neurotransmitter for peripheral pain signals This action is mediated by SP-C SP acting centrally is analgesic This action is mediated by SP-N SP-N research may yield new analgesics.

SUMMARY 1. SP-N offers great hope for development of new drugs: For Cognitive Enhancement For Parkinson’s disease For Alzheimer’s disease 2. Much research is needed to develop these drugs 3. Financial support is required for progress in this field.