S. Mathison et al., NASAL ROUTE FOR DIRECT DELIVERY OF SOLUTES TO THE CENTRAL-NERVOUS-SYSTEM - FACT OR FICTION, Journal of drug targeting (Print), 5(6), 1998, pp. 415-441
During this century, several investigators reported that certain virus
es, metals, drugs, and other solutes could bypass systemic circulation
and enter the brain and/or cerebrospinal fluid directly following nas
al administration. Although evidence clearly suggests that the olfacto
ry epithelium and its olfactory cells play a major role, little is kno
wn about the mechanisms of direct transport of solutes into the brain.
An overview of what is known about these mechanisms may aid in furthe
r research in this field, including studies of direct drug delivery to
the central nervous system. This review, in addition to summarizing t
he literature to date, clearly describes the intricate association of
the anatomical features involved in direct entry of solutes into the b
rain following nasal administration. To aid in the understanding of th
e possible routes a solute can take after nasal administration, the an
atomy of the olfactory epithelium and surrounding tissues is described
, and a detailed scheme delineating the emerging pathways is presented
. Techniques used in delineating these pathways and studies supporting
a particular pathway are discussed in greater detail. Finally, some f
actors influencing the direct transport of solutes to the cerebrospina
l fluid and brain are summarized.