Here are 2 studies:
This one says that limonele can inhibit serotonin and dopamine
Limonene inhibits methamphetamine-induced locomotor activity via regulation of 5-HT neuronal function and dopamine release. - PubMed - NCBI
This one says that anti anxiety properties might be related to GABA
Sub-chronic effects of s-limonene on brain neurotransmitter levels and behavior of rats. - PubMed - NCBI
This one says that limonele can inhibit serotonin and dopamine
Limonene inhibits methamphetamine-induced locomotor activity via regulation of 5-HT neuronal function and dopamine release. - PubMed - NCBI
This one says that anti anxiety properties might be related to GABA
Sub-chronic effects of s-limonene on brain neurotransmitter levels and behavior of rats. - PubMed - NCBI