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LAURA TEIXIDÓ Y COLS. AN. R. ACAD. NAC. FARM.

dos zonas diferentes, la corteza frontal y el hipocampo. Las corrientes registradas
fueron activadas por el receptor nicotínico o por el receptor nicotínico o musca-
rínico de la acetilcolina. Se probaron los efectos de diferentes agonistas nicotínicos
como acetilcolina, nicotina y yoduro de 1,1-dimetil-4-fenil-piperazinio (DMPP), y
antagonistas del receptor nicotínico como a-bungarotoxina y d-tubocurarina en los
oocitos transplantados. Detectamos cuatro clases de cinéticas de corrientes nico-
tínicas. Las diferencias en la amplitud y en la carga eléctrica total de las corrientes
provocadas por varios agonistas en el rango de potencial mantenido no fueron
significativas, excepto en el caso del DMPP a un potencial mantenido de -90 mV.
Nuestros resultados indican que las formas a4ß2, a3ß4 y a7 son los principales
receptores nicotínicos en el cerebro humano.

Palabras clave: Córtex humano.—Corrientes nicotínicas neuronales.—Oocitos
de Xenopus.—Trasplante de membrana.—Alzheimer.—Banco de cerebros.

INTRODUCTION

The cholinergic pathways in the central nervous system play a
significant role in cognitive and behavioral functions such as
learning, memory, arousal, cerebral blood flow and metabolism.
Neuronal nicotinic and muscarinic receptors are involved in these
functions (1-3).

The neuronal nicotinic acetylcholine receptors are a family of
acetylcholine-gated ion channels which has been characterized
combining molecular cloning and pharmacology. Several subtypes
with a specific pharmacology, physiology and anatomical
distribution, have been found. A gene family encoding 11 of these
receptors, has been identified, and most of them have been cloned
and expressed in transfected cells (4). Two main subunits have been
documented: a and b chains. To date 8 types of a and 3 types of ß
chains have been detected. Mutations in one of the subunit genes
account for some pathological conditions such as a specific form of
epilepsy or schizophrenia and in neurodegenerative illnesses, such
as Alzheimer’s and Parkinson’s disease, high affinity neuronal
nicotinic acetylcholine receptors sites are reduced (3).

Studies of recombinant neuronal nicotinic receptor expressed in
Xenopus oocytes show that coexpression of the a and ß subunits is
needed to form an active receptor with a pentameric structure.

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