Behavioral Consequences of Delta-Opioid Receptor Activation in the Periaqueductal Gray of Morphine Tolerant Rats

<table>Changes in
nociception following microinjection of deltorphin into the vPAG. Nociception
was assessed 20 and 50 minutes after deltorphin microinjection into the vPAG of
rats made tolerant to morphine. Pretreatment with morphine produced a slight decrease
in hot-plate latency in rats made tolerant to 10 mg/kg of morphine compared to
the slight increase in rats made tolerant to 20 mg/kg of morphine, although
neither of these changes differed significantly from the effects of deltorphin
administration in saline-pretreated controls. All rats were tested on the hot
plate 20 minutes after deltorphin microinjection (see sample sizes in the
caption of Figure <a href="../fig1/">1</a>), but only a subset was tested at 50 minutes for the saline (<i>N</i>  =  9), 5
(<i>N</i>  =  5), 10 (<i>N</i>  =  10), and 20 (<i>N</i>  =  8) mg/kg morphine groups.</table>

Neural Plasticity

fig2

Figure 2

Figure 2: Behavioral Consequences of Delta-Opioid Receptor Activation in the Periaqueductal Gray of Morphine Tolerant Rats 