Modulation of hippocampal theta rhythm by the opioid system of the pedunculopontine tegmental nucleus.
The pedunculopontine tegmental nucleus (PPN) belongs to the brainstem system which synchronizes hippocampal activity. Theta relevant intra-PPN circuitry involves its cholinergic, GABA-ergic and glutamatergic neurons and Substance P as neuromodulator. Evidence that PPN opioid elements also modulate the hippocampal theta is provided here. In urethane-anesthetized rats a unilateral microinjection of morphine (MF) (1.5 and 5 microg) increased the maximal peak power of tail pinch-induced theta. The higher dose also increased the corresponding frequency. When the theta was evoked by intra-PPN injection of carbachol (10 microg), the addition of MF (5 microg) prolonged theta latency and shortened the duration of the theta. These effects of MF were blocked by naloxone (5 microg). The results obtained suggest that the PPN opioid system can enhance or suppress the hippocampal theta depending on the actual level of PPN activation.
Leszkowicz
Emilia
E
Department of Animal Physiology, University of Gdańsk, 24 Kładki St., 80-822 Gdańsk, Poland.
Kuśmierczak
Magda
M
Matulewicz
Paweł
P
Trojniar
Weronika
W
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000758:Anesthesia; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000502:physiology; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D018847:Opioid Peptides / Q000502:physiology; D045042:Pedunculopontine Tegmental Nucleus / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical; D013826:Theta Rhythm / Q000187:drug effects*
D000701:Analgesics, Opioid; D018679:Cholinergic Agonists; D018847:Opioid Peptides; D009020:Morphine; D002217:Carbachol