Hyperpolarization-activated channels in trigeminal ganglia innervating healthy and pulp-exposed teeth.
OBJECTIVE
To use immunocytochemistry for determining the expression of HCN1, HCN2 and HCN3 (three subunits of the hyperpolarization-activated cyclic nucleotide-gated current channel) in rodent trigeminal ganglia (TG) that innervate healthy teeth and determine if expression of HCN subunits is increased in TG following pulp exposure.


METHODS
Pulps were exposed in right maxillary incisors of male Sprague-Dawley rats. After fixation, TG were removed, cryostat sectioned, and immunocytochemistry was utilized to study the expression of HCN1-3 subunits. Immunoreactivity of individual neurons from the maxillary region of the TG was determined with ImageJ software. Differences in the number immunopositive neurons amongst groups were tested for statistical significance with either a Yates or Pearson's chi-square or Fisher's exact probability tests depending on neuron sample size. Differences in the intensity of immunoreactivity between groups were tested for statistical significance with a Student's t-test.


RESULTS
The majority of TG neurons were immunopositive for HCN1-3. Moreover, statistically significant increases in the number of TG neurons immunopositive for HCN1 and the intensity of HCN1-3 immunoreactivity were observed within hours of exposing the tooth pulp.


CONCLUSIONS
HCN1-3 expression, as determined by immunocytochemistry, is increased within hours after injury. Given that I(h) can facilitate neuronal excitability, results of the current study suggest that antagonists to HCN1-3 subunits could work as analgesics in the alleviation of orofacial pain.
Wells
J E
JE
School of Dental Medicine, Southern Illinois University, Alton, IL 62002, USA. jwells@siue.edu
Rowland
K C
KC
Proctor
E K
EK
D000818:Animals; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000032:analysis*; D003782:Dental Pulp / Q000293:injuries* / Q000294:innervation; D003789:Dental Pulp Exposure / Q000378:metabolism*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000032:analysis*; D008297:Male; D015221:Potassium Channels / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012668:Trigeminal Ganglion / Q000166:cytology*
D054815:Cyclic Nucleotide-Gated Cation Channels; C578667:Hcn1 protein, rat; C578712:Hcn2 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels