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.