Histochemical study of the pre- and postnatal development of acetylcholinesterase in the rat spinal cord

The distribution of acetylcholinesterase (AChE)-positive structures in the developing rat spinal cord was studied with AChE-histochemistry. AChE-positive perikarya were first seen on embryonic day 14 (E14) in the ventrolateral portion of the spinal cord. From that time onward, AChE-containing cells appeared gradually in the intermediate gray, dorsal horn and lateral spinal nucleus of the spinal cord in a ventral-to-dorsal, and lateral-to-medial order. No obvious rostral-to-caudal sequence was found. At birth, the distribution pattern of AChE-positive perikarya was basically similar to that in adults. After birth a dramatic increase in the AChE staining intensity extended from postnatal day 5 (P5) to postnatal day 21 (P21). In addition, two phases of transient AChE staining were observed in the external surface of the dorsal horn from embryonic day 15 (E15) to embryonic day 21 (E21) and in the marginal layer from embryonic day 21 (E21) to postnatal day 14 (P14), respectively.