Mesencephalic trigeminal neurons are innervated by nitric oxide synthase-containing fibers and respond to nitric oxide.
In the present study we found that mesencephalic trigeminal (Mes-V) neurons of the rat are innervated by nitrergic fibers and that nitric oxide (NO) modifies the electrophysiological properties of these cells. Mes-V neurons were surrounded by a network of fibers that contained neuronal nitric oxide synthase (nNOS); these fibers gave rise to terminal-, bouton-like structures which ended in Mes-V cells bodies. These cells, which did not display nNOS-like immunoreactivity were immunoreactive to a cGMP antibody. By performing intracellular recordings in the adult rat brain slice preparation, the effects of diethylenetriamine/NO adduct (DETA/NO) applications were examined. DETA/NO induced a depolarization that averaged 2.2 mV (range: 1-6 mV) in nine of 22 neurons. In 15 of 22 neurons (68% of the cells), there was a decrease in current threshold from 0.74 to 0.60 nA (19%; P<0.001). The excitatory effects of DETA/NO were abolished by ODQ, a blocker of soluble guanylate cyclase. Input resistance (R(in)) decreased in 80% of the cells from a mean of 24.8 to 20.6 Momega (17%; P<0.001) and the membrane time constant (tau(m)) decreased from 7.5 to 5.6 ms (25%; P<0.05). The 'sag' seen in the membrane response of these cells to current pulses was augmented during DETA/NO application. These findings indicate that there is a nitrergic innervation of Mes-V neurons and that these sensory cells are target for NO that may act on them as an excitatory neuromodulator promoting the synthesis of intracellular cGMP.
Pose
Inés
I
Departmento de Fisiología, Facultad de Medicina, Gral Flores 2125, Montevideo, Uruguay.
Sampogna
Sharon
S
Chase
Michael H
MH
Morales
Francisco R
FR
D000818:Animals; D002772:Cholera Toxin; D006152:Cyclic GMP / Q000378:metabolism; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006735:Horseradish Peroxidase; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008406:Masseter Muscle / Q000294:innervation / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009412:Nerve Fibers / Q000187:drug effects / Q000201:enzymology*; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000502:physiology*; D052248:Nitric Oxide Synthase Type I; D011073:Polyamines / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014276:Trigeminal Nerve / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D011073:Polyamines; C005391:diethylenetriamine; D009569:Nitric Oxide; D002772:Cholera Toxin; D006735:Horseradish Peroxidase; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D009252:NADPH Dehydrogenase; D006162:Guanylate Cyclase; D006152:Cyclic GMP