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Prostaglandin E1 (PGE1) when micro-injected into the preoptic anterior hypothalamus (PO/AH) of conscious rabbits is a potent pyrogenic agent. We have investigated the action of PGE1 on the activity of single units of the PO/AH area using the microelectrophoretic technique. One hundred and thirty-eight PO/AH units were tested both for their response to changes in local PO/AH temperature and for their response to PGE1 application. Less than 9.0% of the total population of units tested showed any response to PGE1 application. When present, the response was invariably one of mild facilitation. No specific unit type (thermally sensitive or insensitive) appeared to be selectively affected by PGE1. Thus, the proportion of units affected by PGE1 was constant at 8-10% for warm-sensitive, cold-sensitive, or thermally insensitive units. There was no evidence to support an antagonistic role for PGE1 on the effects on norepinephrine on PO/AH units. On the basis of these results, we cannot predicate any simple neuronal basis for the action of PGE1 in producing fever in conscious rabbits. However, it is suggested that the action of PGE1 might be the modulation of presynaptic release of neurotransmitter onto the units of the PO/AH area.

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