D. Lundberg

Dopaminergic interaction with the respiratory control system in the rat

Apomorphine given to rats lightly anesthetized with halothane produces a dose dependent increase in respiratory frequency and minute ventilation. Although basal arterial CO2 tensions were not significantly altered by apomorphine, the mechanical response to exogenous CO2 exposure was greatly increased in rats given apomorphine. Haloperidol returned the apomorphine-stimulated respiratory pattern to control values. It is concluded that dopamine neurons may have important interactions with respiratory control.

Evidence that respiratory depression by serotonin agonists may be exerted in the central nervous system

Resting with CO2 stimulated respiration were measured by means of a whole body plethysmograph in rats lightly anesthetized with halothane. The respiratory effects of different doses of the serotonin precursor 5-HTP, and the serotonin agonist 5-methoxy-N,N-dimethyltryptamine were studied as well as the effects of a serotonin antagonist methysergide and p-chlorophenylalanine, an inhibitor of serotonin synthesis. The serotonergic agonists decreased tidal volume and minute volume in a dose dependent manner and produced a respiratory acidosis. The respiratory depressant effect was antagonized by methysergide, and the serotonergic antagonist and synthesis inhibitor alone stimulated respiration. Rats given intraventricular 5-methoxy-N,N-dimethyltryptamine also evidenced a decrease in tidal volume, and this response was greater in animals given 5,7-dihydroxytryptamine. It seems likely that CNS serotonin receptors are involved in the control of both basal and CO2 stimulated respiration.

CENTRAL DOPAMINERGIC MODULATION OF THE RESPIRATORY CONTROL SYSTEM

ABSTRACT Rats treated neonatally with intracisternal (i.c.) 6-hydroxydopamine (6-OHDA) or control rats were lightly anesthetized with halothane and placed in a closed body plethysmograph. Rats treated with 6-OHDA had a decreased basal respiratory frequency and a greater apomorphine-induced elevation in the respiratory rate. Moreover the tidal volume response to CO 2 exposure was also greater than in control rats. It is concluded that central catecholaminergic neurons are involved in the respiratory control system.

IN VIVO CYCLIC NUCLEOTIDE CONTENT: EFFECTS OF DOPAMINERGIC AGONISTS AND ANTAGONISTS

ABSTRACT Apomorphine, methylphenidate and d-amphetamine increased cerebellar guanosine-3′,5′-monophosphate (cGMP) whereas bromocryptine did not. All of the antipsychotic drugs tested except sulpiride antagonized this increase. None of these drugs altered adenosine-3′,5′-monophosphate (cAMP) in the striatum. Paralysis antagonized the apomorphine-induced rise in cerebellar cGMP.