Effects of ethanol on the dorsal raphe nucleus and its projections to the caudate putamen.
Level 5 - mechanism / opinion, no new human data
Non-human animal experimental study.
PubMed 11435023 · doi:10.1016/s0741-8329(01)00126-4
What was done
Adult male Wistar rats received intraperitoneal ethanol to examine its effects on dorsal raphe nucleus (DRN) serotonin neuronal activity and terminal release in the rostral caudate putamen (CPu). In the first experiment, microdialysis measured extracellular serotonin in the CPu after acute ethanol (1.75 and 2.5 g/kg) and evaluated rapid tolerance with a 2.5 g/kg challenge 24 hours after ethanol or saline pretreatment. In the second experiment, firing rates of DRN serotonin neurons were measured after 2.5 g/kg ethanol administration.
What was found
Intraperitoneal ethanol at 2.5 g/kg significantly increased extracellular serotonin in the CPu to 150%–160% of baseline (P < .005). Pretreatment 24 hours earlier with 2.5 g/kg ethanol had no effect on the CPu serotonin response to a 2.5 g/kg challenge. Conversely, 2.5 g/kg ethanol significantly reduced DRN serotonin neuron firing rates to approximately 50% of control (P < .005). No specific numerical data were reported for the 1.75 g/kg dose.
Why it matters
The study demonstrates a dissociation between ethanol's suppression of serotonin cell body firing and its increase of extracellular serotonin at terminal projection sites, indicating local terminal release or reuptake inhibition without 24-hour rapid tolerance.
Limits
The study was conducted in male rodents, limiting direct generalizability to humans and excluding female subjects. Sample sizes were not reported in the abstract. The exact cellular mechanism causing elevated striatal serotonin despite reduced raphe firing was hypothesized but not definitively isolated.
Cited by
- contradicts Alcohol consumption initially stimulates serotonergic neurons in the brainstem, specifically in the median raphe and dorsal raphe, to release more serotonin.