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A PERIPHERAL CHOLINERGIC PATHWAY MODULATES STRESS-INDUCED HYPERTHERMIA IN THE RAT EXPOSED TO AN OPEN FIELD.
Citation:
Rowsey, P J., Y. YongLu, AND C J. Gordon. A PERIPHERAL CHOLINERGIC PATHWAY MODULATES STRESS-INDUCED HYPERTHERMIA IN THE RAT EXPOSED TO AN OPEN FIELD. Presented at Experimental Biology, Orlando, FL, 3/30/2001-4/3/2001.
Description:
Exposure to an open-field is psychologically stressful and leads to an elevation in core temperature (Tc). This increase in Tc associated with open-field is usually referred to as stress-induced hyperthermia (SIH) and can be blocked centrally with cyclooxygenase inhibitors such as sodium salicylate and indomethacin. Methyl scopolamine (MS), a peripheral muscarinic antagonist, and pyridostigmine (PYR), a peripheral carbamate that inhibits acetylcholinesterase, do not cross the blood brain barrier and have little effect on Tc in resting, non-stressed animals. However, we have found that MS has an antipyretic effect on Tc caused by handling and cage switch stress. To this end, we assessed the effects of MS and PYR on SIH. Male Sprague Dawley rats at 90 days of age were housed individually at an ambient temperature (Ta)of 22 EC. Tc and motor activity were monitored by radiotelemetry. The open field chamber consisted of an illuminated Plexiglass box (61 x 61 x 61 cm) maintained at a Ta of 22 EC. Rats were dosed IP at 1200 hr with 1.0 mg/kg MS, 0.1 mg/kg PYR, a combination of MS and PYR, or saline and placed immediately inside the open field chamber for 60-min. Tc of controls increased by 1.7 EC during open field exposure. SIH was suppressed immediately by MS and enhanced by PYR. Tc only increased by 0.3 EC in the MS treated animals. The hyperthermic repsonse in the PYR group was nearly 0.6 EC above that of rats dosed with saline. PYR reversed the effect of MS on SIH. These data support a peripheral cholinergic mechanism that controls SIH in the male rat. This abstract does not necessarily reflect US EPA policy.