OLFACTORY AND HORMONAL INFLUENCES ON BASAL FORE-BRAIN OF MALE RAT

1. 1. Single units in the medial forebrain bundle and elsewhere in the preoptic area of anesthetized male rats responded to electrical shocks of the olfactory bulb and to odors. The odor responses were mediated by the olfactory bulb. Inhibitory responses were recorded more often in the preoptic area than in the olfactory bulb and were mainly recorded from units located in more ventral and posterior parts of the basal forebrain than units with excitatory responses. 2. 2. Responses to odors were recorded from single units in the mesencephalic reticular formation, and in the EEG. 3. 3. Changes in firing rates of units in the mesencephalic reticular formation were more closely associated with changes in the EEG than firing rates of units in the preoptic area or olfactory bulb. 4. 4. Administration of testosterone directly into the preoptic area or by systemic injection influenced the electrical activity of preoptic units. Direct preoptic administration increased the magnitude of single unit responses to electrical shock of the olfactory bulb and to odors. Systemic administration had more complex effects, including increases in response magnitude and reversals of response direction. 5. 5. Testosterone effects were also detected in single unit recording in the olfactory bulb and the mesencephalic reticular formation, in olfactory bulb wave activity and in the EEG. © 1969.