Neurons form extensive and dynamic networks where they transmit information through electrochemical signals called action potentials. Astrocytes are the most abundant glial cells in the brain. Astrocytes play a crucial role in regulating neurotransmitters such as gamma-aminobutyric acid and glutamate, which are essential for neural communication and neurotransmission. However, the role of astrocytes has traditionally received less attention in basic research and medicine.
In her doctoral dissertation, Annika Ahtiainen examined how astrocytes influence neuronal connectivity and modulate electrophysiological and biochemical responses in neuron-astrocyte networks. In her research, Ahtiainen cultured neuron and neuron-astrocyte networks on microelectrode arrays (MEAs), which enable real-time extracellular recording of neuronal electrical activity. The activity of the cells was modulated using chemical compounds such as ketamine and gabazine, as well as by a novel electrical stimulation technique, temporal interference stimulation (TIS).
Ketamine is widely used as an anesthetic and in treating depression. Gabazine, on the other hand, can be used, for example, to model epilepsy in laboratory models, as it increases the electrical activation of neurons, creating epileptic-like conditions. TIS is a novel non-invasive electrical stimulation method that has been shown in animal and human studies to activate deep brain regions. TIS is hoped to provide a safer alternative to invasive deep brain stimulation techniques to treat neurological diseases.
Ahtiainen’s findings reveal that the relative proportion of astrocytes within a neural network significantly affects neuronal electrophysiological and biochemical responses. Astrocytes enhanced neuronal responses to gabazine, increasing neuronal network activity. Additionally, both ketamine and gabazine influenced intracellular signaling pathways in neuronal and neuron-astrocyte networks. Astrocytes also modulated the effects of TIS, reducing its impact on neuronal electrophysiological activity.
"Our results show that astrocytes are much more than just supporting cells. They actively shape neuronal activity and influence how neural networks respond to external stimuli. This study provides new perspectives on how neuron-astrocyte interactions regulate neuronal function under different modulatory mechanisms. These findings may help improve our understanding of central nervous system dysfunctions at the cellular level and their effects on both neurons and astrocytes,” Ahtiainen explains.
"When developing new temporal interference-based deep brain stimulation methods, future studies should focus especially on understanding the mechanisms of TIS at the cellular level. A deeper understanding of the effects of TIS on neurons and astrocytes could help develop more effective and non-invasive electrical stimulation therapies," Ahtiainen adds.
Public defense on Friday 4 April
The doctoral dissertation of MSc Annika Ahtiainen in the field of Neuroscience titled In Vitro Neuron-Astrocyte Networks and Their Modulation on Microelectrode Arrays will be publicly examined at the Faculty of Medicine and Health Technology at Tampere University 12 o’clock on Friday 4.4.2025 in the auditorium F115 at Kauppi campus, Arvo building (Arvo Ylpön katu 34, Tampere). The Opponent will be Professor Anna Herland from KTH Royal Institute of Technology, Stockholm, Sweden. The Custos will be Associate Professor Jarno Tanskanen from Tampere University.