Serotonin, the superior colliculus, and grooming behavior in cats with neocortical lesions

Bi-directional, chemically specified neural connections between the subfornical organ and the midbrain raphe system

Reports of a serotonin-immunoreactive fiber plexus in the subfornical organ (SFO) and evidence that this input is relevant to the control of thirst and blood pressure by the SFO prompted an investigation of neural connections between the SFO and the serotonergic neurons in the raphe system. Serotonin-immunoreactive fibers were found to enter the SFO by a number of different routes and to form a plexus in the central part, which contains a bed of fenestrated capillaries. Injections of the anterogradely transported lectin, phaseolis vulgaris leucoagglutinin (PHA-L), into the dorsal raphe nucleus produced a pattern of labeled fibers in the SFO comparable to that revealed with the anti-serotonin staining. Injections into the SFO of the retrogradely transported dye, Fast Blue, labeled cell bodies in the dorsal and median raphe nuclei of the midbrain, and at least 60% of these cells also demonstrated serotonin immunoreactivity. Injections of PHA-L into the SFO identified a return projection to this part of the raphe system, where an angiotensin-immunoreactive plexus of fibers and varicosities is found. Injections of True Blue into various parts of the midbrain raphe nuclei reliably labeled neurons in the SFO, and some 56% of them could also be stained with anti-angiotensin. It is suggested that this circuitry is involved in the control of fluid balance by the SFO and that the serotonergic-raphe projection to the SFO may participate in the relay of visceral sensory information, perhaps related to blood pressure, from the nucleus of the solitary tract and the lateral parabrachial nucleus.

Oral dyskinesia in brain-damaged rats withdrawn from a neuroleptic: implication for models of tardive dyskinesia

Rats with ablated frontal sensorimotor cortex and one with ablated sensorimotor connections to forebrain showed more vacuous chewing movements following 6-week chronic administration of a neuroleptic than did occipitally damaged rats or normal controls who were treated in the same way. The effect was still present 1 month after withdrawal. It was not clearly enhanced by subsequent treatments. Other behaviors (e.g., walking, rearing, or grooming) were not similarly affected by drug withdrawal. Additional results of terminal probes with amphetamine, apormorphine, and haloperidol are described, including movements labeled 'sham eating', observed only in frontal rats given apomorphine (AP). The results are interpreted in terms of a Jacksonina model of levels of brain organization; such a model may be applicable to tardive dyskinesia, seen in many schizophrenic patients who are maintained on neuroleptics for long periods.