Abstract
The median and dorsal (MR and DR) raphe nuclei are the origin of serotonin (5-HT)-containing neurons that innervate the forebrain. Neurons originating in the medial and lateral habenula provide an extensive afferent input to the midbrain that could serve as a negative feedback circuit. The present study was undertaken to establish whether intact habenula nuclie are required to observe the depressant effects of cocaine on the neural activity of 5-HT somata in te DR. To this end, the spontaneous activity of DR.5-HT neurons was assessed in male rats that had previously received bilateral radiofrequency lesions of the habenula complex either 1-4 h (short term) or 7 days (long term) prior to extracellular recordings of single 5-HT neurons of the DR. In rats with short-term lesions, the inhibitory response to cocaine was significantly attenuated. The mean dose to inhibit activity by 50% (ID50) was increased from 0.68 mg/kg in controls to 2.5 mg/kg in lesioned rats. Short-term habenula lesions also significantly decreased the numbers (but not the firing rates) of 5-HT neurons encountered in the DR. In contrast, the dose-response to cocaine as well as the numbers and firing rates of 5-HT neurons found in rats with long-term habenula lesions did not differ from controls. These results suggest that the inhibitory effects of cocaine on DR 5-HT neuronal activity depend in part on the ability of cocaine to affect habenula control of raphe 5-HT function.
Original language | English (US) |
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Pages (from-to) | 555-560 |
Number of pages | 6 |
Journal | Pharmacology, Biochemistry and Behavior |
Volume | 49 |
Issue number | 3 |
DOIs | |
State | Published - Nov 1994 |
Keywords
- Cocaine
- Dorsal raphe
- Electrophysiology
- Habenula
- Rat
- Serotonin (5-HT)
- Single-unit recording
ASJC Scopus subject areas
- Biochemistry
- Toxicology
- Pharmacology
- Clinical Biochemistry
- Biological Psychiatry
- Behavioral Neuroscience