Reduction in cervical probing analgesia by repeated prior exposure to cold-water swims.

Previous work has established that stimulation of the vaginal cervix (cervical probing: CP) and cold-water swims (CWS) each produce analgesia in rats that is affected similarly by catecholaminergic mechanisms, but differentially by serotoninergic and opioid mechanisms. The present study examined whether CP analgesia, like CWS analgesia, would be reduced by prior repeated CWS exposure. Tail-flick latencies were significantly increased by CP and CWS in naive animals. In animals chronically preexposed to 14 daily swims, CP analgesia was reduced and CWS analgesia was reduced at 60, but not 30 min after the swim. After 1 month of recovery, CP analgesia showed a persistent reduction, whereas CWS analgesia was fully recovered. These data suggest that the mechanisms underlying CP and CWS analgesia are interrelated.