LATERAL TEGMENTAL FIELD NEURONS SENSITIVE TO MUSCULAR-CONTRACTION - AROLE IN PRESSOR REFLEXES

The medullary lateral tegmental field (LTF) has a major role in sympat hetic nerve discharge (SND) rhythmicity, but its role in presser refle xes generated by hindlimb muscular contraction (MC) is unknown. Theref ore, two sets of experiments were performed in 17 chloralose-urethane anesthetized cats. First, responses of single LTF neurons to MC induce d by L7-S1 ventral root stimulation were examined, The majority (30 of 47) of LTF neurons increased firing during MC. Most LTF neurons had a basal discharge correlated with the 2-10 Hz rhythm of SND or the card iac cycle and responded to increases in blood pressure, Only seven neu rons were inhibited by MC, most having a respiratory rhythm. Second, p resser responses to MC and to caudal hypothalamic stimulation were exa mined before and after bilateral LTF microinjections of a synaptic blo cker (CoCl2) as well as with lidocaine, Microinjection of CoCl2 or lid ocaine significantly attenuating the dominant 2-10 Hz power coefficien t of SND had no effect on the presser responses to MC or caudal hypoth alamic stimulation. Therefore, LTF may be important for basal rhythms in SND and may help synchronize SND during MC, but its contribution to basal rhythms is apparently not required for presser reflexes evoked by hindlimb MC or hypothalamic stimulation.