Morphine dependence increases the response to a brief pentylenetetrazol administration in rat hippocampal CA1 in vitro.
OBJECTIVE
Herein we used electrophysiologic approaches in hippocampal area CA1 to estimate how morphine treatment alters the pentylenetetrazol (PTZ) effects.


METHODS
Hippocampal slices taken from either control animals or animals made dependent via chronic morphine administration were examined. Changes in the population spike and epileptiform amplitudes were used as indices to quantify the effects of PTZ exposure in the control and morphine-dependent slices. Hippocampal slices taken either from control animals or from animals made dependent upon morphine were exposed to PTZ, either with or without morphine, naloxone, or morphine + naloxone.


RESULTS
Morphine dependence increased a PTZ-induced long-term potentiation (LTP) of the population spike in CA1 in vitro. This LTP was not found in rats that had spontaneously withdrawn morphine or withdrawn with naloxone in vivo after chronic morphine intake. Morphine or naloxone in vitro blocked the PTZ-induced LTP changes in control and morphine-dependent slices. However, PTZ-induced multiple population spikes (epileptiform activity) in CA1 was not blocked by naloxone.


CONCLUSIONS
It is concluded that dependence on morphine enhances PTZ-induced plastic and epileptic changes in CA1 excitability. We suggest that this model of neuronal activity in dependent slices could present an opportunity for studying the mechanisms underlying the increased likelihood of seizures in morphine users.
Jafarzadeh
Zakaria
Z
Department of Physiology, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Fathollahi
Yaghoub
Y
Semnanian
Saeed
S
Omrani
Azar
A
Salmanzadeh
Feresteh
F
Salmani
Mahmoud Elahdadi
ME
D000818:Animals; D003292:Convulsants / Q000494:pharmacology*; D004195:Disease Models, Animal; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects* / Q000503:physiopathology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009020:Morphine / Q000008:administration & dosage; D009021:Morphine Dependence / Q000188:drug therapy / Q000209:etiology / Q000473:pathology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000008:administration & dosage; D009434:Neural Pathways / Q000502:physiology; D010433:Pentylenetetrazole / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D018709:Statistics, Nonparametric; D013375:Substance Withdrawal Syndrome / Q000473:pathology / Q000503:physiopathology
D003292:Convulsants; D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D009020:Morphine; D010433:Pentylenetetrazole