Detection of tyrosine hydroxylase (TH) immunoreactivity within the VTA, (low magnification, left panel). VTA combined immunohistochemistry and in situ hybridization showing at high magnification (right panel) neurons expressing TH (green cells), glutamic acid decarboxylase mRNA (GAD 65/67; purple cells), vesicular glutamate transporter 2 mRNA (VGluT2; green or white grain aggregates) or combinations of these cell markers. Abbreviations. Left: RLi- Rostral Linear Nucleus, IF- Interfasicular Nucleus, PBP- Parabrachial Pigmented Nucleus, PN- Paranigral Nucleus, SNc- Substantia Nigra Pars Compacta, fr- fasciculus retroflexus, mp- Mammillary Peduncle, Right: TH- tyrosine hydroxylase, GAD- glutamic acid decarboxylase, VGluT2- vesicular glutamate transporter 2.