Distribution pattern of acetylcholinesterase in the Diencephalic nuclei of Hemidactylus flaviviridis

Abstract

Diencephalon is the part of forebrain which comprises epithalamic, dorsal and ventral thalamic and hypothalamic parts. Neuroanatomically diencephalon is very significant comprising a large area and plenty of nuclear groups. In the present study, distribution pattern of enzyme acetylcholinesterase (AChE) has been carried out in the diencephalon of Indian wall lizard Hemidactylus flaviviridis, by employing a modified histochemical technique to visualize AChE stained nuclei described by Hedreen, J.C. et.al. (1985).
Acetylcholinesterase is an effective marker of cholinergic and cholinoceptive neurons since it hydrolyses neurotransmitter acetylcholine in to choline and acetate at synaptic clefts. Present histochemical results exhibited a widespread distribution of acetylcholinesterase in the different diencephalic nuclei of Hemidactylus flaviviridis from rostral to caudal sections in a mosaic pattern. Most of the thalamic nuclei demonstrated intense activity for acetylcholinesterase. Among the dorsal thalamic nuclei, nucleus dorsolateralis thalami, nucleus medialis thalami and dorsal corpus geniculatum nucleus exhibited intense activity. Among the ventral thalamic nuclei, nucleus ventromedialis thalami, nucleus ventrolateralis thalami, nucleus supra-peduncularis showed intense reaction for AChE. In hypothalamus, magnocellular nuclei demonstrated very high intensity while parvocellular nuclei showed moderate to intense activity at different levels.
Present study establishes that thalamic nuclei are intricately connected to other brain centres with cholinergic involvements and hypothalamus being a neurosecretory part shows mosaic pattern of AChE activity.
In conclusion, the abundance of cholinergic innervations in the thalamic and hypothalamic areas, is a well conserved feature of vertebrates particularly among tetrapods. Present investigation has been compared with the homologous nuclei of other vertebrates studied earlier.