Substance P-immunoreactive neurons in the rostromedian area of the midbrain send axons to the lower spinal cord in the chicken

Morphological Analogy of the Rostral Midline Area in the Chicken Midbrain to the Anteromedian Nucleus in the Mammalian Midbrain.

“…In addition, the present study showed that most of the RMA neurons exhibited SP-immunoreactivity and these SP-IR neurons projected to the spinal cord. Corresponding to these data, previous immunohistochemical studies in the spinal cord demonstrated the presence of SP-IR fibers in the spinal preganglionic region in mammals [2] and in birds [4,9]. Furthermore, physiological studies showed that preganglionic neurons in the spinal cord were functionally supported by SP [1,6].…”

“…Sci. 62(8): 909-911, 2000 In the course of our study on substance P (SP)-immunoreactive (SP-IR) neurons in the central nervous system of the chicken, we found that many SP-IR neurons were clustered in the midline area of the rostral midbrain [9]. Cytoarchitecturally, this neuron cluster was identified as a clearly isolated cell group comprised of small neurons deeply stained with cresylviolet (outlined area on the right side of the section in Fig.…”

“…1A). We call this neuron cluster the rostral midline area of the midbrain (RMA) tentatively [9]. On the other hand, it has been known that a small neuron group called the anteromedian nucleus (AM) exists in the midline area of the mammalian midbrain.…”

“…The sections were subjected to the immunohistochemistry for SP as described previously. Finally, the sections were treated with 0.1% DAB-0.003% H 2 O 2 .In the third experiment, to identify whether or not the RMA is a continuation of the Edinger-Westphal nucleus (EW), EW neurons were retrogradely labeled by injection of 30% HRP (10 µl, Type II, Toyobo, Osaka, Japan) into the ciliary ganglion of 2 chickens under anesthesia by sodium pentobarbital (20 mg/kg) (refer to Naito et al [9] for the detailed description of the methods).The most rostral part of the RMA appeared in the midline area at the level of the posterior commissure. Progressing caudally, the RMA shifted dorsolaterally along the central gray substance (Fig.…”

“…In the third experiment, to identify whether or not the RMA is a continuation of the Edinger-Westphal nucleus (EW), EW neurons were retrogradely labeled by injection of 30% HRP (10 µl, Type II, Toyobo, Osaka, Japan) into the ciliary ganglion of 2 chickens under anesthesia by sodium pentobarbital (20 mg/kg) (refer to Naito et al [9] for the detailed description of the methods).…”