Real-time monitoring of endogenous noradrenaline release in rat brain slices using fast cyclic voltammetry. 2. Operational characteristics of theα2 autoreceptor in the bed nucleus of stria terminalis, pars ventralis
1993; Elsevier BV; Volume: 607; Issue: 1-2 Linguagem: Inglês
10.1016/0006-8993(93)91498-h
ISSN1872-6240
AutoresPeter Palij, Jonathan A. Stamford,
Tópico(s)Neurotransmitter Receptor Influence on Behavior
ResumoFast cyclic voltammetry (FCV) at carbon fibre microelectrodes was used to monitor stimulated noradrenaline (NA) efflux in slices of the ventral part of the rat bed nucleus of stria terminalis (BSTV) superfused with artificial cerebrospinal fluid at 32°C. NA efflux was evoked by local electrical stimulation (trains of 10–50 pulses, 0.2 ms duration, 10 mA constant current at 10–500 Hz). The effects of four α2 antagonists (yohimbine, rauwolscine, parazosin and WB 4101) and threeα2 agonits (clonidine, oxymetazoline and UK 14304) were examined. All drugs (1 μM) were added via the superfusate. Yohimbine and rauwolscine increased NA efflux on the lower but not the higher frequency trains: maximum increases (on 20 Hz, 50 pulse stimulation) were to392±63% (yohimbine) and243±7% (rauwolscine). There was a threshold train duration for demonstration of autoreceptor antagonism of 500–1000 ms. Prazosin and WB 4101 did notincrease NA efflux but caused a modestdecrease at the higher (100–500 Hz) frequencies. The effects of theα2 agonists were also affected by stimulus train duration. Longer trains reduced agonist (clonidine) effects. When tested on pseudo-one pulse (POP) stimulations (less than 100 ms duration), theα2 agonists decreased NA efflux. UK 14304 reduced NA efflux on 20 pulse/200 Hz stimulation to a g reater degree (86±7%) than the partial agonists clonidine (39±3%) or oxymetazoline (40±8%). The present results demonstrateα2 autoreceptors are a major mechanism in the control of NA efflux in the BSTV. The lack of potentiation of NA efflux by prazosin suggests that the autoreceptor is not of theα2B orα2C subtype while the clear inhibitory action of oxymetazoline suggests anα2A orα2D receptor. With appropriate selection of stimulation conditions, the actions, of both antagonists and agonists (partial and full) can be examined.
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