SINGLE CELL RECORDINGS FROM TSETSE (GLOSSINA M-MORSITANS) ANTENNAE REVEAL OLFACTORY, MECHANO AND COLD RECEPTORS

Action potentials from individual cells and receptor potentials were r ecorded from antennae (funiculi) of living tsetse flies, Glossina m.mo rsitans Westwood, using a 'surface-contact' recording technique. Stimu li were pressure of the electrode, changes in temperature and the vapo urs of 1-octen-3-ol, acetone, 3-methylphenol, dichloromethane and CO2. Two types of mechanoreceptive cells were found. One type only fired a ction potentials when pressure was increased, the other type continued firing when pressure was maintained. Of the 182 cells tested for thei r sensitivity to temperature change and the odour stimuli, 19% did not respond to any of the stimuli, suggesting that we are still unaware o f cues which may be of import to the flies, and 4% responded to temper ature only, increasing and decreasing their activity with a decrement and increment in temperature, respectively. Of the 141 cells which wer e olfactory receptors, 52% responded to 1-octen-3-ol and 40% were excl usively sensitive to this substance. For 3-methylphenol these percenta ges were 23 and 18, for acetone 13 and 11, for dichloromethane 12 and 7, for CO2 13 and 13. No clustering of cell types in certain areas of the funiculi was found, nor was a difference apparent between the sexe s. The majority of the olfactory cells responded by increasing their a ctivities on odour stimulation. Inhibition was found in three cells on ly, in which spontaneous activity was suppressed on stimulation with 3 -methylphenol. Spike responses were phasic-tonic and varied between tw o extremes: Cells showing relatively rapid cessation of spike activity after the end of stimulation, and cells which continued firing for se veral seconds or minutes after stimulation. Possible behavioural effec ts of the activities of the various cell types are discussed.