Buznikov_1987_Zh.Evol.Biokhim.Fiziol_23_423

The neurotransmitters found in early ("pre-nervous") embryos of Metazoa operate at the intracellular level. In these embryos, the transmitter receptors (or their functional equivalents) and adenylate cyclase coupled with them are localized intracellularly. Intracellular functions of neurotransmitters may be also found in the differentiated neurons of adult animals.