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Neurotransmitter phenotypes of intermediate zone reticular formation projections to the motor trigeminal and hypoglossal nuclei in the rat
Author(s) -
Travers Joseph B.,
Yoo JiEun,
Chandran Ravi,
Herman Kenneth,
Travers Susan P.
Publication year - 2005
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20604
Subject(s) - neuroscience , biology , gabaergic , spinal trigeminal nucleus , cholinergic , brainstem , glutamate receptor , hypoglossal nucleus , reticular formation , choline acetyltransferase , vesicular acetylcholine transporter , glutamatergic , cholinergic neuron , anatomy , nucleus , inhibitory postsynaptic potential , biochemistry , receptor , nociception
Abstract Numerous studies suggest an essential role for the intermediate (IRt) and parvocellular (PCRt) reticular formation (RF) in consummatory ingestive responses. Although the IRt and PCRt contain a large proportion of neurons with projections to the oromotor nuclei, these areas of the RF are heterogeneous with respect to neurotransmitter phenotypes. Glutamatergic, GABAergic, cholinergic, and nitrergic neurons are all found in the PCRt and IRt, but the projections of neurons with these phenotypes to the motor trigeminal (mV) and hypoglossal nucleus (mXII) has not been fully evaluated. In the present study, after small injections of Fluorogold (FG) into mV and mXII, sections were processed immunohistochemically to detect retrogradely labeled FG neurons in combination with the synthetic enzymes for nitric oxide (nitric oxide synthase) or acetylcholine (choline acetyltransferase) or in situ hybridization for the synthetic enzyme for GABA (GAD65/67) or the brainstem vesicular transporter for glutamate (VGLUT2). In three additional cases, FG injections were made into one motor nucleus and cholera toxin (subunit b) injected in the other to determine the presence of dual projection neurons. Premotor neurons to mXII (pre‐mXII) were highly concentrated in the IRt. In contrast, there were nearly equal proportions of premotor‐trigeminal neurons (pre‐mV) in the IRt and PCRt. A high proportion of pre‐oromotor neurons were positive for VGLUT2 (pre‐mXII: 68%; pre‐mV: 53%) but GABAergic projections were differentially distributed with a greater projection to mV (25%) compared to mXII (8%). Significant populations of cholinergic and nitrergic neurons overlapped pre‐oromotor neurons, but there was sparse double‐labeling (<10%). The IRt also contained a high proportion of neurons that projected to both mV and MXII. These different classes of premotor neurons in the IRt and PCRt provide a substrate for the rhythmic activation of lingual and masticatory muscles. J. Comp. Neurol. 487:28–47, 2005. © 2005 Wiley‐Liss, Inc.