0-TESTO COMPLETO.pdf - Fondazione Santa Lucia

TEL.14 – Manipulation of serotonin transmission on behavioural and neurochemical deficits…
The mechanism by which excess PHE interferes with brain amine synthesis
is not yet well known. Indeed, excess PHE could influence cortical aminergic
transmission by reducing brain availability of amino acid precursors, tyrosine
and tryptophan, or by inhibiting hydroxylase activity. Submitted data
(see preliminary results, point 3) demonstrated that activity of tryptophan
hydroxylase enzyme (TPH) in pFC is deficient in PKU-affected mice, that
brain tryptophan availability is not deficient, and that 5-hydroxytryptophan
(5-HTP) treatment restore serotonin (5-HT) neurotransmission, also in presence
of high PHE blood levels. These data renew interest for 5-HTP treatment
in hyperphenylalaninemia (HPA): it is commercially available, has been used
clinically for over 30 years, can be easily administered as dietary supplement
and is well tolerated [Turner et al. 2006].
So, effects of 5-HTP treatment, administered during critical developmental
period (P14-P21), on behavioural profile of ENU2 mice, is an important
objective in this project. By these experiments we would to respond to following
question: can you prevent mental retardation in PKU subjects by increasing
pharmachologically (by 5-HTP) serotonin levels during critical period?
Preliminary results demonstrated ability to prevent alterations of spine morphology
in medial pFC neurons of PKU mice (see preliminary data, point 2).
Thus, we hypothesize that preventing deficits of 5-HT levels during a critical
period for brain maturation we prevent behavioural deficits in adult PKU
mice. Effect of 5HTP will be evaluated on behavioural test performances
(Object Recognition Test, Spatial Novelty Test, Spontaneous Alternation Test,
Morris Water Maze in standard and modified protocols) in adult ENU2 mice.
We expect a recovery of more general cognitive deficits (as object and spatial
novelty recognition, and spatial learning in standard Morris Water Maze),
while deficits in more specific frontal-dependent cognitive functions (as learning
and memory in the Spontaneous Alternation Test and in modified Morris
Water Maze) would be maintained.
2. HPA refers any consistent excess of blood PHE levels, including classical
PKU. There are also several intermediate degrees of HPA, in which blood
PHE levels are mildly elevated.
Accumulated evidences indicate that even mildly elevated blood PHE levels
promote cognitive deficits involving pFC. So, our second objective is the
development of animal models of different degrees of HPA (control, mild
HPA, mild PKU and classic PKU) on the base of plasma PHE concentrations.
Different concentrations of blood PHE interfere differently with cognitive
functions. In particular we retain that different forms of HPA present different
profiles, characterized by crescent seriousness of behavioural symptoms moving
from mild HPA to classical PKU forms, and major impairment of brain
aminergic synthesis and transmission. Behavioural and neurochemical phenotyping
will be performed on control, mild HPA, mild PKU and classic PKU
mice.
For behavioural phenotyping, all mice will be submitted to several behavioural
tests to evaluate motor (Open Field Test, Rotarod Test and Grooming
activity), cognitive (Object Recognition Test, Spatial Novelty Test, Spontaneous
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