The neural processes of acoustic information was investigated in examples of Ensifera. Sound reception by these insects has two main functions: localization and recognition of the sound source. This study investigated aspects of each of these processes.

This study Is concerned with the behavioural and ecological aspects of the acoustic interaction that occurs when two bush cricket species, Platycleis albopunctata and Metrioptera roeselii. sing together. The effects of the interaction are predominantly one-way and result in inhibition of singing activity by albopunctata, or a change in its song pattern. 'Ibis behaviour was initially described by Broughton in I965 who also described song changes in other species resulting from interactions with singing allospecifics. The present study continues this research into song modification in insects. The extent of natural variation is examined in detail in the song of albopunctata. The acoustic behaviour of this species when singing with conspecifics is also examined in detail. The songs and singing behaviour of some other bush cricket species are analysed and tested for susceptibility to modification. These latter studies, though less detailed than the study on the albopunctata/roeselii interaction, have contributed to the formation of hypotheses as to the causation of song modification. The results indicate that insects with songs of similar frequency content are liable to interact acoustically. Species which show slight readjustments in song output when singing with conspecifics are also liable to song modification especially when the song of the influencing Insect is more continuous in nature than the song of the Influenced insect. The results of the detailed analysis of the albopunctata/roeselii interaction reveal a complex interplay between endogenous rhythms of motivation displayed in the singing activity of albopunctata, and parallel inhibitory and excitatory factors from the song of the roeselii. Much of the fieldwork has been undertaken in France v/here, in many localities, albopunctata and roeselii are sympatric. Song modification in the wild is usually prevented by a negative phonotactic response by albopunctata to the song of roeselii» This response may be derived from preexisting behavioural patterns that result in 'territorial' spacing between males in grassland populations. In habitats where populations overlap, interspecific spacing develops with the onset of singing activity by the adults. In this way albopunctata is excluded from certain localities by high-density roeselii populations due to the acoustic competition between these two species.

The enlarge vagal and facial lobes of the carp are associated with the presence of large numbers of taste buds located respectively, within the oropharynx, especially on the palatal organ, and on the body surface, in particular the barbels.

The taxonomy of the Order Passeriformes, at the family level and above, is still in considerable flux. An historical review of the taxonomy, including traditional studies, and more recent works (particularly DNA-DNA hybridization), is given. The present study attempted to analyse little used characters, i.e. those on the plantar surface of the foot, of over five hundred species of bird. Large amounts of variation and homoplasy were found. Compatibility analysis (by a LeQuesne test computer program) was used to find cliques of compatible characters for families, and other groups of Passeriformes. The polarities of character state changes were hypothesized by outgroup comparison, with non-passerines from a number of orders. Some characters were found to be linked to the scansorial habit, others of reasonable use taxonomically, and yet others, not obviously adaptive, showed so much homoplasy as to be almost worthless taxonomically. Useful characters were then used to describe and define families, and in some cases other taxonomic groups, attempts were made, with varying degrees of success, to allocate 'problem genera'. The same characters were used to construct cladograms, and then other informative characters (i.e. those which define subgroups within the cladogram, but show homoplasy) were added, to produce one or more trees of each group investigated. The results were compared to those of earlier studies, based on morphological, anatomical and biochemical characters. The degree of congruency varied considerably. It was particularly interesting to find that in some cases there was a reasonable fit with the results of DNA-DNA hybridization.

This study Is an investigation into the behaviour of male bushcrickets of the genus Metrioptera. The situation investigated was that arising when the males of different species are placed in the same enclosure. A large number of such experiments was made and in each case observations were made on the movements of the insects, particularly with respect to one another. Their stridulations were recorded and subsequently analyzed with a view to detecting influences by the song of one insect upon song production by the other. Attempts were made to relate the behaviour to that observed in similar circumstances when the two males belonged to the same species. In the latter cases, clearly recognisable aggression and homosexual courtship were much commoner, and there was a much stronger tendency for the defeated insect to return to the victor in one species, influence of pre-conflict caging conditions was studied. Four species of Metrioptera were utilised: M. roeselii (HAGENBACH), M. brachyptera (L.), M. bicolor (PHILIPPI), and M. sepium (YERSIN). Nearly all of the experiments were confined to the first three species. It was found that the stridulations of roeselii and bicolor tended to inhibit song output in brachyptera. In interactions between roeselii and bicolor, either insect could be inhibited, but it was more often bicolor. A visit was made to a German locality where roeselii and bicolor occurred naturally in the same place, and inhibition effects were observed to take place between them in the field. One brachyptera out of thirteen tested produced chirps with more syllables than usual, when exposed to roeselii song. It did not modify its chirps in response to bicolor song, perhaps because of the more discrete nature of the latter. The phenomenon is discussed in relation to Broughton'S (I965) discovery of song modification in Platycleis denticulata (PANZER).

Mammalian spermatozoa acquire the capacity for motility during passage through the epididymis. This study on rat spermatozoa shows that pH, cAMP and protein kinase C (PKC) all play an important role in the initiation of motility. pH has the most critical role and until the initial pH change in spermatozoa has occurred between the caput and caudal epididymal regions of the rat, second messengers are not effective in stimulating motility, but they are involved once such pH change has occurred. The spermatozoa of Fucus serratus differ from mammalian spermatozoa in that they are released into the sea prior to fertilisation and the motility of these spermatozoa is initiated upon their release into sea water. The ionic composition of sea water plays an important role in this activation and it is evident that the presence of Na+ is vital for the Initiation of motility. This study shows that a Na+/H+ exchanger, a N+-dependent bicarbonate/chloride exchanger and a Na+/K+ pump, which regulate the concentration of Na+, are present in Fucus serratus and integrated activity of these exchangers/pumps causes an increase in intracellular pH (pHi). An elevation in pHi correlates to an increase in motility, mediated through the activation of the dynein ATPase of the flagella. Motility and respiration of these spermatozoa are closely linked, probably because the ATP produced by respiration is used primarily by the dynein ATPase. Second messengers have also been Implicated in the initiation/regulation of motility and respiration. Indirect evidence shows cAMP and PKC are present and regulate motility, possibly through the phosphorylation and thereby activation of key regulatory proteins, such as the Na+/H+ exchanger. A rise in intracellular Ca2+ is also associated with the activation of Fucus serratus spermatozoa but the exact mechanism by which such a rise regulates motility remains unclear.

In a series of experiments investigating a possible post-coitum contraceptive, it was observed that the numbers of corpora lutea (CL) of pregnant Sprague-Dawley (CD) rats were greater than in cyclic, unmated control females (p < 0.001). The ontogeny of these supplementary CL (SCL) was established by the recording the mean number of CL in pregnant Sprague-Dawley rats on days 1 to 9 post-coitum (day 1 being the first day post-coitum) using the gross phological dissection of the ovary. Compared to cyclic controls, an initial significant increase in mean CL numbers was recorded on day 1 post-coitum (p < 0.05) with a further significant increase between days 5 and 7 (p < 0.001). This phenomena was neither Sprague-Dawley strain, nor pregnancy specific, as a similar increase was also recorded for Wistar rats between days 4 and 7 postcoitum and identical increases in mean CL numbers were recorded in pseudopregnant rats of both strains. Histological studies of ovarian tissue confirmed the presence of newly formed CL on day 5 and 6 post-coitum and an absence of entrapped ova; follicular development was also present in early pregnancy with Graafian follicles evident on day 4 post-coitum. Plasma progesterone determinations revealed no increase in circulating progesterone as a result of SCL formation in either pregnant or pseudopregnant rats. Supplementary ovulations may be initiated by the preimplantation surge of oestrogen, on day 4 post-coitum, as treatment with the anti-oestrogen. Tamoxifen, inhibits their formation. Investigations into the presence of an appropriately-timed preovulatory surge of gonadotrophins in the early stages of pregnancy however, proved inconclusive. Supplementary ovulation occurs therefore between day 4 and 7 post-coitum in both pregnant and pseudopregnant Wistar and Sprague-Dawley rats, probably initiated by a consistent physiological event. This phenomena therefore obviously has an impact on the estimation of embryo mortality studies in this species.

The effects of antidepressant drugs on central beta-adrenergic and dopaminergic receptor function were investigated using the anorexic effects of low doses of amphetamine and apomorphine as assays of beta-adrenergic function and presynaptic dopamine function respectively. Anorexia was typically examined using a microstructural analysis of feeding, which was validated observationally. Amphetamine anorexia was characterized by a decrease in eating time and an increase in eating rate. At 0.5 mg/kg both beta-adrenergic and dopaminergic antagonists reversed anorexic effects, whilst anorexia at 1.0 mg/kg was reversed by dopaminergic antagonists only. An enhancement of amphetamine anorexia was seen following acute desmethylimipramine treatment! this effect was exactly compensated for over chronic treatment, implying no net change at beta-adrenergic synapses. However, applying amphetamine intracranially showed that approximately 75% of the acute enhancement of amphetamine anorexia was mediated peripherally, suggesting an attenuation of beta-receptor function during chronic antidepressant drug treatment. Some further data suggested that an alpha-adrenergic change could also have contributed to the antidepressant drug-induced attenuation of anorexia. Low doses of apomorphine, specific for presynaptic dopamine receptors, induced an anorexia characterized by decreases in both eating time and eating rate. The dopamine receptor antagonists haloperidol and thioridazine reversed apomorphine anorexia by reversing eating time but not eating rate. Administration of apomorphine into nuclei A9 and A10 reduced total food intake and eating time but not eating rate. These findings imply that presynaptic dopamine receptors mediate the effects of apomorphine on eating time. Acute treatment with desmethylimipramine, enhanced apomorphine anorexia. During chronic treatment the apomorphine-induced reduction in eating time was sometimes attenuated, suggesting a presynaptic dopamine receptor subsensitivity. Anorexia was also enhanced following acute desmethylimipramine treatment with intracranial administration of apomorphine. Again, there was no clear evidence of subsensitivity following chronic treatment, but some evidence for subsensitivity in nucleus A10 during withdrawal. The significance of a reduced beta-receptor function and an increased dopamine function following chronic antidepressant drug treatment are discussed in relation to the biological basis of depression.

Biochemical investigations were undertaken to study the glutamate (L-glu) and aminobutyric acid (GABA) receptors in the central nervous system (CNS) of the American cockroach, Periplaneta americana. The aim was to provide a simple, quick and cost effective method of screening new chemical entities as potential insecticides acting on these systems, and to provide structure activity information once a series had been suggested as active in these systems.

Low doses of dopamine autoreceptor (DA) agonists are presumed to act by stimulating DA autoreceptors on the sona/dendrites and axon terminals of DA neurons. Low doses of apomorphine reduced food Intake, in a microstructural analysis paradigm, by reducing both the time spent feeding and the rate of food ingestion. The reduction of eating time was shown to result from the stimulation of DA autoreceptors located on the cell bodies and dendrites of the mesolimbic DA system. The reduction of eating rate however, appeared to result from the activation of axon terminal DA autoreceptors. The significance of this dissociation is discussed in relation to the mechanisms through which presynaptic DA receptors on the same neuron may subserve different behavioural functions. The observation that apomorphine administration resulted in a selective manipulation of the microstructural parameters of feeding, was then used to assess the action of antidepressant drugs on DA autoreceptor function. In both normal and chronically stressed rats, chronic antidepressant treatment failed to alter the sensitivity of DA autoreceptors. However, on withdrawal, the sensitivity of cell body DA autoreceptors appeared reduced, as apomorphine no longer in any way influenced the time spent feeding in the microstructural paradigm. The Implications of these findings are discussed in relation to the hypothesis that antidepressant drugs increase DA function by reducing the sensitivity of presynaptic DA receptors.