serotonin icon logo on blue circle with brush texture

acetylcholine adenosine adrenaline anandamide anatomy biology brush button care cell chemical circle depression design diagram dopamine education element epinephrine graphic healthcare histamine hormone hydrogen icon illustration logo medicine molecule mood narcotic neuron neurotransmitter nitric norepinephrine opioid oxide oxytocin scheme science serotonin sign signal somatostatin structure substance symbol synapse texture vector