Assessment of Acetylcholinesterase Enzyme (AChE) Activity in the Developing Brain of TSD Lizard, Calotes Versicolor (Daud.)

Abstract

Acetylcholinesterase (AChE) is a critical enzyme in the neuronal cholinergic system of vertebrates. It is one of the efficient cholinesterases that is involved in the termination of acetylcholine-mediated neurotransmission, rapidly hydrolyzing acetylcholine into acetate and choline. Barring a few reports on the distribution/presence of AChE enzyme activity in the adult reptilian species there are nil reports on the presence of this enzyme activity in the developing brain. Hence, the present investigation aims to evaluate AChE enzyme activity in the developing brain of an oviparous lizard, Calotes versicolor which exhibits a novel Female-Male-Female-Male (FMFM) pattern of temperature-dependent sex determination (TSD). The eggs were collected during breeding season, padded with moist cotton, and incubated in an incubator at 30o C. The whole brain from the embryos was collected during different developmental stages from oviposition (Stage 27) to hatching (stage 42). The AChE enzyme activity was quantified in the brain, according to Ellman’s protocol using a spectrophotometer. The findings reveal that the onset of AChE enzyme activity is observed as early as at oviposition, which reflects the early action of AChE activity in the developing brain. The observed results albeit indirectly suggest the involvement of AChE enzyme activity in the morphogenetic process. Further, an exponential increase in AChE activity during the post-gonadal differentiation phase indicates age-related elevation in AChE enzyme activity which in turn unveils its involvement in neuronal transmission of the embryonic brain. Besides, this specific AChE enzyme activity in the developing brain of Calotes versicolor represents a conserved pattern for the cholinergic system in vertebrates.