Differential participation of hippocampal formation in cocaine-induced cortical electroencephalographic desynchronization and penile erection in the rat.
We evaluated the role of the hippocampal formation in cocaine-induced cortical electroencephalographic (EEG) desynchronization and penile erection. Adult, male Sprague-Dawley rats anesthetized and maintained by chloral hydrate were used. Intravenous (1.5 or 3.0 mg/kg) administration of cocaine dose-dependently increased intracavernous pressure (ICP), our experimental index for penile erection. This was accompanied by desynchronization of EEG activity recorded from the somatosensory cortex (cEEG), as represented by a decrease in root mean square (RMS) and an increase in mean power frequency (MPF) values. There was a simultaneous increase in the RMS values, without significant changes in the MPF values of EEG signals recorded from the hippocampal formation (hEEG). In animals that received prior application of 10% xylocaine either intrathecally (i.t.) at the L6-S1 spinal levels or directly into the bilateral hippocampal formation, the RMS values of both cEEG and hEEG signals induced by cocaine (1.5 or 3.0 mg/kg, i.v.) were appreciably reduced, along with a further increase in ICP. Unilateral microinjection of cocaine (15 or 30 microg) into the hippocampal formation elicited discernible excitation of both cEEG and hEEG signals. Intriguingly, the ICP underwent a significant and dose-dependent reduction, which was discernibly antagonized by i.t. application of xylocaine. We conclude that cocaine may effect cortical EEG desynchronization but cause a reduction in ICP via an action on the hippocampal formation.
Institute of Pharmacology, National Yang-Ming University, Tapei, Taiwan, Republic of China.
A Y
AY
Chang
J Y
JY
Chan
L Y
LY
Tsen
S H
SH
Chan
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology*; D003344:Cortical Synchronization; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D004569:Electroencephalography / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006624:Hippocampus / Q000033:anatomy & histology / Q000502:physiology*; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D010410:Penile Erection / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects; D013346:Subarachnoid Space / Q000502:physiology
D018765:Dopamine Uptake Inhibitors; D008012:Lidocaine; D003042:Cocaine