Increase in testosterone metabolism in the rat central nervous system by formalin-induced tonic pain.
The effects of formalin-induced tonic pain (FITP) on testosterone (T) concentrations in the central nervous system (CNS) and serum were investigated in rats. T was nearly eliminated from the brain and spinal cord 1.5 and 24 h after a single subcutaneous injection (100 microl/rat, sc) of 5% formalin and its levels were similar to that seen following castration. In serum, T concentrations were decreased significantly 1.5 h following formalin injection, but after 24 h, the serum level of T was within normal range. T concentrations in the brain, spinal cord, and serum were not modified 20 min after formalin injection. Pretreatment of rats with finasteride, a 5alpha-reductase (5alpha-R) inhibitor (5 mg/kg, sc) blocked T elimination from the brain and spinal cord by FITP, but it failed to prevent decrease in serum T. However, 3 h after administration of exogenous T (5 mg/kg, sc), FITP did not cause a significant decrease in T levels in the CNS and serum. These results suggest that FITP eliminates endogenous T in the brain and spinal cord by increasing 5alpha-R activity in the CNS.
Amini
Hossein
H
Department of Pharmacology, Neuroscience Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran.
Ahmadiani
Abolhassan
A
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002490:Central Nervous System / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018120:Finasteride / Q000494:pharmacology; D005557:Formaldehyde; D008297:Male; D009919:Orchiectomy; D010146:Pain / Q000139:chemically induced* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism; D013739:Testosterone / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D013997:Time Factors
D004791:Enzyme Inhibitors; D005557:Formaldehyde; D013739:Testosterone; D018120:Finasteride