The expression level of tyrosine hydroxylase (TH) was quantified to
examine if changes in the dopaminergic pathway were affecting the
behavioural responses in both two genotypes. TH is the enzyme
responsible for catalyzing the conversion of the amino acid L-tyrosine
to L-3,4-dihydroxyphenylalanine (L-DOPA) (Molinoff PB, Axelrod J.
Biochemistry of catecholamines. Annual Review of Biochemistry.
1971;40:465–500). In neurons TH is localized in the pre-synaptical
compartment and acts as the rate-limiting enzyme of catecholamine
biosynthesis. Evidence from the RT-qPCR data presented in Fig. 2C
demonstrated that the TH expression level at 2dpf in untreatedpanx1a-/- larvae was significantly lower
compared to panx1a+/+ controls
(p-value <0.0001). 6-OHDA treatment for 72hrs decreased
the expression of TH in both panx1a+/+(p-value= 0.049) and panx1a-/-(p-value= 0.002) groups. No attenuation of TH expression after
6-OHDA treatment was found in panx1a-/- larvae
when compared to untreated age-matched mutants (p-value= 0.064).
This result suggested that a significant reduction in TH expression
occurs when the Panx1a function is lost and that 6-OHDA treatment could
not further aggravate the situation.